research papers on black rice

Recent advances on bioactivities of black rice

Affiliation.

• 1 aCollege of Biotechnology, Universidade Federal do Pará & Centre for Valorization of Amazonian Bioactive Compounds, Belém-PA, Brazil bCenter of Investigation in Clinical Nutrition, Université catholique de Louvain, Louvain-la-Neuve, Belgium cLife Sciences Institute, Université catholique de Louvain, Louvain-la-Neuve, Belgium dPharmacognosy research group, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium.
• PMID: 28858891
• DOI: 10.1097/MCO.0000000000000417

Purpose of review: Black rice has been consumed for centuries in Asian countries such as China, Korea or Japan. Nowadays, extracts and derivatives are considered as beneficial functional foods because of their high content in several bioactive molecules such as anthocyanins, other phenolics and terpenoids. The purpose of this review is to summarize and discuss recent developments on black rice bioactivities.

Recent findings: Some sterols and triterpenoids with potential anticancer properties already tested in vitro and in vivo have been isolated and identified from bran extracts of black rice. Protection against osteoporosis has been suggested for the first time for black rice extracts. Because of its antioxidant and anti-inflammatory properties, black rice also protects liver and kidney from injuries. One clinical study reported the interest of black rice in case of alcohol withdrawal.

Summary: Several advances have been recently achieved on the understanding of the potential biological effects of black rice and its derivatives. They further confirm that black rice should be considered as a promising source of health-promoting functional foods targeting a large set of noninfectious diseases. However, more clinical studies are needed to support the findings highlighted in this review.

Publication types

• Anthocyanins / analysis
• Anti-Inflammatory Agents / analysis
• Anti-Inflammatory Agents / pharmacology
• Antineoplastic Agents / analysis
• Antineoplastic Agents / pharmacology
• Antioxidants / analysis
• Antioxidants / pharmacology
• Diabetes Mellitus / prevention & control
• Functional Food*
• Gastrointestinal Tract / metabolism
• Kidney / metabolism
• Liver / metabolism
• Nervous System Diseases / prevention & control
• Obesity / prevention & control
• Oryza / chemistry*
• Oryza / classification*
• Osteoporosis / prevention & control
• Phenols / analysis
• Phenols / pharmacology
• Phytochemicals / analysis
• Phytochemicals / pharmacology
• Terpenes / analysis
• Terpenes / pharmacology
• Anthocyanins
• Anti-Inflammatory Agents
• Antineoplastic Agents
• Antioxidants
• Phytochemicals

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Effect of black rice flour with different particle sizes on frozen dough and steamed bread quality

Protective effect of two thai pigmented rice cultivars against h2o2-induced oxidative damage in ht-29 cell culture.

Radicals derived from exogenous and endogenous sources are considered to be the principal cause of genetic damage. Exogenous and endogenous radicals participate in the reactive oxygen species (ROS) formation, which leads to damages in the DNA, RNA, proteins and lipids. However, dietary compounds, mainly from pigmented rice, are an essential source of antioxidants that help protect cells from damage. This study seeks to determine the antioxidant properties and cytoprotective effect of two Thai pigmented rice extracts namely the glutinous black rice (native name: Neaw dum moa37) and red rice (native name: Hom gradung-nga57) on H2O2-induced damage in HT-29 cells. The bioactive compound contents, as well as antioxidant activities of both rice extracts, were investigated. The protective effect of rice extracts on H2O2-induced damage was executed following the co-incubation method. HT-29 cells were exposed to H2O2 and different rice extract concentrations for 3 h and an MTT assay was used to measure the viability of the cell. The ROS level was determined using the 2′,7′-dichlorofluorescin diacetate (DCFDA). The result showed that glutinous black rice extract contained significantly higher contents of all analysed antioxidants and activities than red rice extract. Glutinous black rice showed a higher cytotoxic effect compared to red rice. At the non-toxic concentration of both rice extracts, the HT-29 cells were guarded against the H2O2 induced oxidative stress. Besides, the intracellular ROS accumulation result from H2O2 exposure was significantly reduced in the presence of rice extracts for both glutinous black rice and red rice compared to control. Hence, this study has demonstrated the potential properties of both pigmented rice extracts in alleviating H2O2-mediated damage in HT-29 cells.

Ultrasound‐assisted extraction of anthocyanin from black rice bran using natural deep eutectic solvents: Optimization, diffusivity, and stability

Black rice anthocyanins alleviate hyperuricemia in mice: possible inhibitory effects on xanthine oxidase activity by cyanidin 3-o-glucoside, phenolic profiles and bioactivities of different milling fractions of rice bran from black rice, sustainable dyeing and functionalization of wool fabrics with black rice extract, metabolite profiling of black rice (oryza sativa l.) following xanthomonas oryzae pv. oryzae infection, growth kinetics and survival of lactobacillus acidophilus in black rice milk, sensory evaluation and antimicrobial activity of snack bar from black soybean and black rice containing anthocyanins.

Snack bars made from black soybean and black rice could be used as a food product to complement the energy and nutrients needs. Both have anthocyanins content in black soybean and black rice as well as the potential as an antimicrobial agent. The purpose of this study was to obtain an optimal formula, evaluate the sensory acceptance, analyze the total monomeric anthocyanin content of the snack bars, and compare the growth of probiotic and pathogenic bacteria in anthocyanins crude extracts from the snack bars. The production of snack bars was done by using three variations of main ingredients, including 30% of black soybean + 70% of black rice (formula 1), 50% of black soybean + 50% of black rice (formula 2), and 70% of black soybean + 30% of black rice (formula 3). The results performed that consumers acceptance for formulas 2 and 3 was not significantly different (P > 0.05), but significantly higher (P < 0.05) than formula 1. Total monomeric anthocyanin content analyzed by the pH differential method in these three snack bars formulas had no significant difference (P > 0.05). The growth analysis of probiotic and pathogenic bacteria showed that the percentage of growth inhibition of Escherichia coli and Salmonella enterica serovar Typhi bacteria was significantly higher (P = 0.00) compared to Lactobacillus acidophilus. Also, formulas 1 and 2 could significantly inhibit E. coli and S. enterica ser. Typhi bacteria (P = 0.00) compared to formula 3. It could be concluded that formula 2 showed the best snack bar based on sensory evaluation and pathogenic bacteria inhibition assay.

Evaluation of Phytochemical Contents and In Vitro Antioxidant, Anti-Inflammatory, and Anticancer Activities of Black Rice Leaf (Oryza sativa L.) Extract and Its Fractions

Black rice leaves (Oryza sativa L.) are a major part of rice straw left in open fields after rice harvest as agricultural waste. In this study, crude ethanolic extract (CEE) and various solvent fractions (hexane (Hex), ethyl acetate (EtOAc), n-butanol (n-BuOH), and aqueous fractions) of black rice leaves were investigated for their bioactive compound contents as well as antioxidant, anti-inflammatory, and anticancer activities. The results demonstrated that among all the fractions, the n-BuOH fraction presented the greatest contents of total phenolics and flavonoids, while anthocyanins were found to be abundant in the n-BuOH and aqueous fractions, which also exhibited powerful antioxidant abilities according to DPPH and ABTS radical-scavenging assays and a reducing power assay. Regarding anti-inflammatory activity, CEE and EtOAc reduced the production of NO and cytokine secretion (PGE2, IL-6, and IL-1β) but displayed less effect on tumor necrosis factor α (TNF-α) release in lipopolysaccharide (LPS)-induced RAW 264.7 cells. They also significantly decreased iNOS and COX-2 protein expression. Additionally, the phenolics-rich ethyl acetate fraction showed the greatest activity against HepG2 liver carcinoma cells, inhibited cell growth, increased the Sub-G1 population, and induced apoptosis via mitochondrion-dependent mechanisms. In conclusion, black rice leaves, a byproduct of rice, exhibited strong antioxidant, anti-inflammatory, and anticancer capacities and might be useful for application in functional foods and the pharmaceutical industry.

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Research, History and Development

• © 2016
• U.K.S Kushwaha 0

Nepal Agricultural Research Council,, Agriculture Botany Division, Lalitpur, Nepal

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Summary of current scientific research on black rice

Unique historical accounts of the origin of black rice

Health benefits and consumption advice on black rice

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Table of contents (10 chapters)

Front matter.

• U. K. S. Kushwaha

Nutrition Profiles of Black Rice

Black, brown, and red rices, economic importance, black rice applications, black rice cultivation, health benefits of black rice, black rice recipes, back matter.

• Rice Crop Genetics
• Anthocyanin
• Anti-Oxidant
• Reactive Oxygen Species
• Health Benefits

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U.K.S Kushwaha

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Bibliographic information.

Book Title : Black Rice

Book Subtitle : Research, History and Development

Authors : U.K.S Kushwaha

DOI : https://doi.org/10.1007/978-3-319-30153-2

Publisher : Springer Cham

eBook Packages : Biomedical and Life Sciences , Biomedical and Life Sciences (R0)

Copyright Information : Springer International Publishing Switzerland 2016

Hardcover ISBN : 978-3-319-30152-5 Published: 04 April 2016

Softcover ISBN : 978-3-319-80733-1 Published: 25 April 2018

eBook ISBN : 978-3-319-30153-2 Published: 19 February 2016

Edition Number : 1

Number of Pages : XX, 192

Number of Illustrations : 6 b/w illustrations, 59 illustrations in colour

Topics : Agriculture , Nutrition , Oxidative Stress , History of Science

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• J Food Sci Technol
• v.57(10); 2020 Oct

Development of lightly milled black rice with easy cooking and retaining health benefits

Porntip sirisoontaralak.

Division of Food Science and Nutrition, Faculty of Agricultural Product Innovation and Technology, Srinakharinwirot University, Nakhon Nayok, 26120 Thailand

Supreeya Keatikasemchai

Chanon mancharoen, nantarat na nakornpanom.

Consumers are reluctant to eat pigmented rice due to cooking difficulties and harder texture than white rice. In this study, paddy samples of black rice (Hom Nil cultivar) were milled for 0, 10, 30, 60 and 100 s and degree of milling (DOM) ~ 0, 6, 12, 22 and 30% were obtained. Head rice yield, physicochemical properties, cooking qualities, nutrients, resistant starch content, antioxidant properties, and sensorial qualities were studied. Milling at 10 s (DOM ~ 6%) did not remove all bran fractions. Head rice yield retained at 70.33%. Lightness (L*) and redness (a*) of black rice remained constant until DOM ~ 20% but yellowness (b*) gradually increased. Nutrients were embedded at different locations in grain kernels. All nutrients decreased with DOM but in different extents. Milling at 10 s generated loss of anthocyanin (70%), fat (44%), ash (33%) and phenolic compounds (31%). Comparably tiny losses were observed in protein (15%) and dietary fiber (25%). However, cooking qualities of black rice were substantially improved. Cooking time reduced from 22 to 15 min with increases in water uptake ratio and volume expansion ratio. Additionally cooked black rice had impressively softer texture. Panelist appreciated the change in odor, flavor, texture attributes and palatability of the rice.

Introduction

Rice ( Oryza sativa L.) is the main staple diet in many Asian countries. With growing health concerns and enlarging markets of healthy food products, some particular rice cultivars are increasingly produced and introduced to consumers in Thailand and worldwide. Among these rice cultivars, black rice is unpolished rice that contains a high content of natural anthocyanin compounds such as cyanidin 3-glucoside and peonidin 3-glucoside in the aleurone layer (Hu et al. 2003 ). It has other valuable antioxidants, including polyphenolics, flavonoids, vitamin E, phytic acid, and γ-oryzanol. Black rice has received wide interest from consumers and food industry owing to antioxidative, anti-inflammatory, antiatherosclerotic, anticancer and lower cholesterol properties (Hu et al. 2003 ). In addition, black rice is a good source of fiber, minerals, and several essential amino acids (Itani et al. 2002 ).

In order to consume rice, the hull is removed from rough rice to obtain brown rice. Brown rice (hulled rice) composes of the embryo (2–3% by weight), surface bran (6–7%), and endosperm (around 90%). Milling (whitening process) subsequently removes germs and bran layers from hulled rice by abrasive or friction forces and provides well-milled, reasonably well-milled, lightly milled, and undermilled rice depended on degree of milling (DOM). DOM is expressed by the weight percentage of bran removed or indicated by visual examination, chemical composition, and optical measurements. Milling induces grain breakage resulting in reduction of head rice yield (Reid et al. 1998 ; Yadav and Jindal 2008 ) and causes losses of food nutrients including fat (Chen and Siebenmorgen 1997 ), neutraceutical lipid (Ha et al. 2006 ), protein (Lamberts et al. 2007 ), dietary fiber (Lai et al. 2006 ), ash (Singh et al. 2000 ; Lamberts et al. 2007 ), phosphorus, magnesium, calcium, copper, manganese, molybdenum, chromium (Doesthale et al. 1979 ), iron (Prom-u-thai et al. 2007 ), zinc (Liang et al. 2008 ) and selenium (Liu et al. 2009 ). For antioxidant properties, phenolic, flavonoids, and anthocyanin content and antioxidant activity decreased after milling (Hu et al. 2003 ; Zhou et al. 2004 ; Walter et al. 2011 ) because more than 50% of polyphenols is in removed pericarp.

Milling devalues the nutritional and health benefits of hulled rice. However, it improves the cooking and sensory quality of rice. Thus, the majority of the consumers prefer well-milled rice, especially in countries where rice is the principal food. Researchers have reported a reduction of cooking time and increases in water absorption during cooking, volume expansion ratio, and length expansion ratio after milling (Mohapatra and Bal 2006 , 2007 ). As a result of change in cooking quality, improved cooked rice texture was observed which included decline in hardness, firmness and chewiness and increases in cohesiveness, adhesiveness and stickiness (Park et al. 2001 ; Mohapatra and Bal 2006 ). Moreover, alteration of sensory attributes in terms of texture and flavor intensity have been reported by Park et al. ( 2001 ). The panelists preferred cooked milled rice more than cooked brown rice (Piggott et al. 1991 ).

Usually, DOM increases with milling time. But, deviations of obtained DOM could be detected among rice cultivars due to differences in kernel characteristics, grain morphological characteristics including grain thickness, grain length, and length-to-width ratio that play an important role in gained DOM (Chen and Siebenmorgen 1997 ; Prom-u-thai et al. 2007 ). Most of the reported works, however, involved rice grains with light brown pericarp color. For this reason, little is known about the effects of milling on DOM and the qualities of black rice.

Certainly, milling creates adverse effects but simultaneously amended rice qualities. However, these changes are dependent on the extent of milling. Thus, the objective of this study was to evaluate the effects of milling on qualities of black rice. The suitable degree of milling was assessed to produce easy-to-cook black rice that exhibit softer texture, desirable sensory quality, and reasonable nutritional and health benefits. It is anticipated that the results of this work will promote black rice consumption among the young generation.

Materials and methods

Dehusking and milling.

Paddy of fragrant black rice, Hom Nil cultivar, was purchased from a local rice mill in Nakorn Sawan province, Thailand. Freshly harvested paddy was cleaned by air classifier to remove the filth. It was dried at 30 °C using a circulated air incubator to a final moisture content of 12–14%. Paddy sample was stored dry and cool (~ 25 °C) less than 30 days before milling and analysis.

Paddy samples (250 g) were dehusked on a laboratory scale rubble roll husker (THU 35A, Satake, Japan). Whole and intact black rice kernels (150 g) were milled in triplicate for 0, 10, 30, 60, and 100 s in the laboratory scale abrasive rice polisher (SKD-DBKK, Satake, Japan) equipped with an automatic timer to obtain rice with different DOM (0–25%). The DOM (the weight percentage of kernel layers removed by milling) was calculated from the weight of rice before and after milling. The screen and rotor of the polisher were thoroughly brushed to remove rice bran and rice kernels. After the whitening process, broken kernels were removed using a test rice length grader set with a 6.2 mm groove grading screen and receiving trough set at an angle of 30° from vertical. (TRG05A, Satake, Japan). The head rice with different DOM was conveyed to quality analysis.

Determination of head rice yield, color and cooking quality

Head rice yield.

After rice kernels milled at different DOM were graded, head rice was separated and weighed. Head rice yield was expressed as a percentage of the weight of milled head rice kernels to the total weight of paddy.

Color of rice grain

Color of rice grain was measured in terms of L* value (lightness), a* value (redness), and b* (yellowness) using a CIE LAB Color Meter (ColorFlex E2, Hunter Lab, USA).

Cooking time

In order to assess the cooking time (C T ), five gram of rice sample was cooked in boiling water (rice: water = 1:20). Cooking time was recorded when nine from ten kernels were completely gelatinized.

Water uptake ratio, volume expansion ratio, length expansion ratio

Water uptake ratio (W UR ), volume expansion ratio (V ER ) and length expansion ratio (L ER ) were determined by cooking 1 g of rice in 15 mL boiling water until the predetermined cooking time (Mohapatra and Bal 2006 ). The water uptake ratio was determined by the weighing of initial raw rice and cooked rice using a digital balance. It was expressed as the ratio of water absorbed during cooking to uncooked rice weight. For volume expansion ratio, the volume of raw rice and cooked rice was measured using the toluene displacement method. The ratio of cooked rice volume to raw rice volume was reported. Similarly, lengths of rice kernels before and after cooking (20 kernels per replicate) were determined by a digital micrometer. The length expansion ratio was presented as the ratio of cooked rice length to raw rice length. In order to evaluate overall cooking quality, the cooking index (CI) was calculated by the formula as follows

Cooked rice hardness

For cooked rice hardness, 10 g of black rice kernels were placed in a beaker and added with 15 mL of water. The rice was cooked in an automatic rice cooker for 45 min with 800 mL of water was poured into the inner pot. The cooked rice sample was kept in the rice cooker for 10 min more. The samples were taken out and cooled at room temperature for 45 min. Then, the texture of cooked black rice was measured using back extrusion tests with a texture analyzer (TA 500, Lloyd Instruments, UK) equipped with a 50 kg-capacity compression load cell. The crosshead speed was 50 mm/min. The back extrusion test cell consisted of a stainless steel cylinder and a spherical-shaped stainless steel plunger. About 4 g cooked rice sample was placed in the cylinder. The plunger was allowed to move downward until it stopped 1 mm above the cell base. The hardness of cooked rice was determined from the maximum extrusion force in terms of Newton (N).

Determination of pasting property

Black rice samples were ground and screened through a 100-mesh sieve. Paste viscosity of black rice flours was determined with a Rapid Visco Analyser (RVA, Model 4D, Newport Scientific, Australia) using the AACC Approved Method 61-02 (AACC 2000 ). The pasting parameters were peak viscosity, breakdown (peak viscosity-minimum viscosity), final viscosity, consistency (final viscosity-minimum viscosity), and setback (final viscosity-peak viscosity).

Determination of nutrients

The protein content of black rice was determined by the combustion method, whereas fat content was measured after solvent extraction (AOAC 2000 ). Ash content was measured using the AACC Approved method 08-01 (AACC 2000 ). Dietary fiber was determined by the AOAC Method 985.29 (AOAC 2000 ).

Determination of phenolic content

Black rice samples were ground and screened through a 40-mesh sieve. Total phenolic content was extracted by modifying the method of Liyana-Pathirana and Shahidi ( 2006 ). Black rice flours (1 g) were extracted at room temperature with 8 mL of 80% ethanol containing 2 mL of NaOH (6 mol/L) in a shaker at 150 rpm for 24 h. Around 2 mL of HCl (5 mol/L) was added to adjust pH of extracts to 1–2 and the flasks were shaken for another 10 min. The extracts were subsequently centrifuged at 12,000 g for 10 min and the supernatants were pooled and stored at 4 °C.

Total phenolic content was measured by the Folin-Ciocalteu colorimetric method. Extracts (2 mL) were mixed with 1 ml Folin-Ciocalteu reagent (0.5 N), and the reaction was neutralized with saturated sodium carbonate (75 g/L). They were incubated at 25 °C for 1 h before the blue color occurred was measured at 760 nm using a spectrophotometer (Spectronic 21, Milton Roy Company, USA) and ethanol as a blank. A calibration curve was prepared using a gallic acid solution. Total phenolic contents were expressed as mg of gallic acid equivalent per 100 g of rice (mg GAE/100 g).

Determination of anthocyanin content

Anthocyanin in the black rice flours was extracted by the method described by Zhu et al. ( 2010 ) with slight modification. Black rice flours (1 g) were extracted by mixing with 10 mL of 80% ethanol acidified with 0.5 mL of HCl (5 mol/L) and stirring on a shaker at 150 rpm for 24 h. The extracts were centrifuged at 12,000× g for 10 min, and the supernatants were decanted to amber bottles for anthocyanin determination.

The total anthocyanin content in black rice was measured by the pH differential method. The anthocyanin extracts (≤ 10 mL) was diluted with 0.025 mol/L potassium chloride buffer (pH 1.0) and 0.4 mol/L sodium acetate buffer (pH 4.5), and subsequently, the absorbance of diluted test portions were read at 520 and 700 nm. Anthocyanin content was expressed as cyanidin-3-glucoside equivalents, as follows:

where A = (A 520nm  − A 700nm )pH 1.0 − (A 520nm  − A 700nm )pH 4.5; MW (molecular weight) = 449.2 g/mol for cyanidin-3-glucoside (cyd-3-glu); DF = dilution factor; l = pathlength in cm; ε = 26 900 molar extinction coefficient, in L  ×  mol –1  × cm –1 , for cyd-3-glu; and 10 3  = factor for conversion from g to mg.

Determination of DPPH radical scavenging activity

Black rice flours (1 g) were extracted by mixing with 25 mL of 80% ethanol acidified with HCl (1% v/v) and stirring on shaker at 150 rpm for 24 h. The extracts were centrifuged at 4000× g for 15 min, and the supernatants were decanted to amber bottles for anthocyanin determination.

Each 1 mL of crude extract was added to 3 mL of 2,2-diphenyl-l picrylhydraxyl (DPPH) (0.05 mmol/L). The mixture was vigorously shaken and left to stand for 30 min at room temperature in the dark. The absorbance of the reaction solution was then measured at 515 nm using a spectrophotometer (Spectronic 21, Milton Roy Company, USA) and ethanol as a blank. A calibration curve was prepared using an ascorbic acid solution. DPPH radical scavenging activity was expressed as mg of ascorbic acid equivalent per 100 g of rice (mg AA/100 g).

Determination of resistant starch content

Resistant starch was analyzed according to Goni et al. ( 1997 ). Around 50 mg of rice flour sample (dry weight) was added with 5 mL distilled water, adjusted pH to 2.0 and incubated with 0.2 mL pepsin solution, which was prepared by dissolved pepsin enzyme with enzyme-to-protein ratio of 1:17 in 0.01 mol/L HCL, at 37 °C for one h. Then it was hydrolyzed at 37 °C for 16 h after adjusting pH to 7.0 and adding 100 μL of α-amylase. Samples were subsequently centrifuged, and the precipitate was added with 2 mL of 2 mol/L KOH. The solution was incubated with 0.1 mL of amyloglucosidase enzyme from Aspergillus niger at 50 °C for 30 min after pH was adjusted to 3.6–4.2. After centrifugation, glucose concentration in the supernatant was determined using the glucose oxidase–peroxidase kit. A factor of 0.9 was applied to convert glucose concentration into starch content.

Assessment of sensory properties

For sensory analysis, black rice samples were cooked in an electric rice cooker for 45 min using rice to water ratio of 1:1.5. Sensory evaluation was performed by 30 Thai students in the Division of Food Science and Nutrition, Srinakharinwirot University, Thailand. A hedonic scale (1 = extreme dislike, 9 = extreme like) was applied to determine panelist’s preference to cooked rice samples. Sensory attributes of cooked rice that were subjected to evaluation were appearance, color, odor, flavor, texture, and overall acceptability.

Data analysis

The milling treatments and all analyses were performed in triplicate. Data were subjected to analysis of variance followed by Tukey’s range test to compare means at p  < 0.05 using SPSS v. 12.0 software. Regression coefficients obtained for the relationship between DOM and black rice qualities were subjected to analysis of variance using SigmaPlot software v.11.0.

Results and discussion

Relationship of milling time and degree of milling.

Black rice was abrasively milled for 0–100 s and various DOM (0–30%) was obtained. Changes of DOM during milling are shown in Fig.  1 . DOM was not linearly increased with milling time. The alteration rate (slope) differed during the milling process. A power function relationship between milling time and DOM was indicated ( R 2  = 0.9951). A decreasing of the slope was observed when milling time was less than 20 s (DOM < 9%). A lower gradient was consistently observed when milling time was during 20–100 s (DOM > 9%).

Effect of milling time on the degree of milling of black rice

Around 9% rice layer removal was indicated as the bran fraction. Lamberts et al. ( 2007 ) further designated 9–15%, 15–25% and > 25% removal as outer, middle and core endosperm fraction respectively. Hardness of rice bran was different from that of endosperm. Outer layer of rice bran was harder than inner layer, whereas the hardness of the three fraction of endosperm was similar. Thus, decreasing of the slope was noticed in the rice bran layer (DOM < 9%) and the shift of slope was subsequently perceived at the edge of bran and outer endosperm fraction (DOM > 9%). This agreed with the findings of Lamberts et al. ( 2007 ).

Additionally, fragrant black rice (Hom Nil cultivar) was easily milled. Milling at 100 s yielded high DOM (~ 30%), whereas it was around 25% for long-grain brown rice (Lamberts et al. 2007 ). Grain morphology affected DOM, particularly in grain length and length-to-width ratio (Prom-u-thai et al. 2007 ). At the same milling time, DOM of long-slender grain was higher than other shapes. The grain of Hom Nil rice was long (length of 7.2 mm) and slender (length-to-width ratio of 3.61). Thus comparatively high DOM was noticed. Singh et al. ( 2000 ) also reported that the percentage of bran removed at successive milling intervals differed significantly in different cultivars due to differences in shape and grain hardness. The loss of bran during milling increased with the length-to-width ratio as well.

Figure  2 a shows the quadratic equation for the relationship between head rice yield and DOM ( R 2  = 0.9732). The removal of bran layers increased with milling duration and consequently, head rice yield (HRY) reduced. At the beginning (milling at 10 s or DOM ~ 6%) HRY was 70.33% and reduced remarkably to 58.97% at 20 s (DOM ~ 9%). A gradually slow reduction of HRY was subsequently noticed with successive milling. It was 27.50% at the end of milling (DOM ~ 30%).

Effect of degree of milling on a head rice yield and b color of black rice

Non-linear relationship between HRY and DOM was confirmed with Yadav and Jindal ( 2008 ). They found that the reduction in HRY was a power function of the milling duration. Sun and Siebenmorgen ( 1993 ) informed dissimilar findings of a linear relationship between DOM and HRY, which implied that rice was milled to greater extents, the HRY decreased linearly. However, the cultivar and milling moisture content significantly influenced the rate at which HRY changes with DOM (Reid et al. 1998 ). The decrease in HRY with DOM was smaller at high moisture content at which the rice was milled. Bran layers were more easily removed when milling moisture content increased. Moreover, there was an indication of a relationship between kernel thickness of a cultivar and the HRY versus DOM slope. Kernel thickness distributions affected interkernel abrasion in friction milling. Lower HRY was obtained when a thickness less than 1.88 mm or more than 2.03 mm (Sun and Siebenmorgen, 1993 ). Black rice (HOM Nil) has a thickness of 1.77 mm; thus comparatively lower HRY was reported. These factors might contribute to the different relationships between HRY and DOM observed among the studies.

Grain color, cooking quality, texture and pasting property of black rice

Figure  2 b presents the quadratic equation for the relationship between Lightness (L*), redness (a*), yellowness (b*), and DOM. R 2 were 0.9807, 0.9439 and 0.9534 respectively. Lightness (L*) of black rice sharply increased (22.8–56.2) until DOM ~ 15% and the increase was subsequently gradual (62.1–69.4). Then L* remained almost constant at DOM ~ 25%. At 15% DOM, bran and outer endosperm were completely removed. Redness of black rice (a*) remained almost constant (4.9–4.3) until DOM ~ 20% before it was gradually decreased (3.5–0.9). Yellowness (b*) of black rice gradually increased (3.1–9.9) until DOM ~ 20% and then it remained almost constant (11.0–11.3).

The bran hull (outermost layer of black rice) contains high anthocyanin content, which contributes to the dark purple color of the black rice kernel. Changes of grain color during milling black rice indicated that the amount of pigment decreased from the bran surface to the middle endosperm fractions. Bran and outer endosperm fraction contained more pigments than the other portions. The distribution of pigments was consistent in the core endosperm in which the pigment extent was meager. Although Chen and Siebenmorgen ( 1997 ) reported the linear relationship of grain whiteness and DOM, Lamberts et al. ( 2007 ) and Yadav and Jindal ( 2008 ) confirmed a rapid increase of grain lightness at the beginning and a gradual increase in latter stages of milling. They claimed that the bran layer was quickly removed when compared to a mixture of bran and starchy endosperm layer. Distribution of pigments in brown rice kernels might be slightly different from those in black rice kernels. In brown rice, lightness remained unchanged in the middle and core endosperm fraction due to the removal of red and yellow pigments mostly located in bran layers. Distinct increase at the early stage of milling was due to significant loss of purple pigment in bran layers. However, the lightness of black rice still increased in middle endosperm fraction. This occurred concurrently with an increase of yellowness.

Cooking qualities of black rice milled for different milling times are shown in Table ​ Table1. 1 . The cooking time of black rice was around 22 min, and it was significantly shortened to 15 min ( p  < 0.05) at 10 s milling (DOM ~ 6%). The water uptake ratio (0.66) and volume expansion ratio (1.39) significantly increased ( p  < 0.05) when milling at 10 s as well. There was no significant difference between the length expansion ratio and milling time ( p ≥  0.05). Conclusively cooking index significantly increased ( p  < 0.05) with 30 s milling.

Effect of milling on cooking qualities and pasting viscosity of black rice

All values are means ± standard deviation (n = 3)

Breakdown = peak viscosity-minimum viscosity, Consistency = final viscosity-minimum viscosity, Setback = final viscosty-peak viscosity

Different letters within the same column are significantly different at p  < 0.05

In addition to cooking quality, the texture of cooked black rice changed with different milling time (Table ​ (Table1). 1 ). Cooked black rice had a hardness of 34.75 N, but the substantially softer texture was noticed when milling only 10 s (22.37 N). Milling for a longer time (30–100 s) did not generate notable changes of texture ( p ≥  0.05).

Good cooking qualities of rice are high volume expansion ratio, length expansion ratio, water uptake ratio and minimum cooking time. Removing of bran layers after milling assisted more water diffusion into the kernels during cooking because total protein content and surface lipid reduced. Starchy endosperm without fibrous bran layer was easily cooked and had a short cooking time. Positive effects of the degree of milling on water uptake, volume expansion, and cooking index were exhibited in the study of Mohapatra and Bal ( 2006 ) and Mohapatra and Bal ( 2007 ) as well. A sharp increase in cooking index was also observed at 9–14% DOM. Cooking qualities did not change much when most of the bran layer was removed at high DOM. However, they found a linear increase in length expansion with DOM. Thickness and surface area of fragrant black rice might differ from three varieties of brown rice used in their study. Similarly, DOM had a negative effect on the hardness of cooked brown rice. Existence of bran layer induced rigidity to cooked rice kernels. Moreover, the effect of DOM on cooking qualities varied with ranges of DOM, cooking method (cooking using fixed water-to-rice ratios or cooking using excess water), and pretreatment (parboiled rice or non-parboiled rice) (Brilliris et al. 2012a , b ).

From Table ​ Table1, 1 , peak viscosity, final viscosity, and breakdown increased ( p  < 0.05) after milling. Significant difference ( p  < 0.05) was attained at 30 s of milling (DOM ~ 12%). But setback decreased ( p  < 0.05) significantly when milling at the same milling time. There was no significant difference found among consistency values ( p ≥  0.05).

Total starch increased linearly with DOM when bran, outer, and middle endosperm fractions were removed (Lamberts et al. 2007 ). More starch portions in the flour sample increased peak viscosity, final viscosity, and breakdown of high DOM rice. Additionally, starchy endosperm without fibrous bran layer readily absorbed water and swelled comfortably. This finding agreed with Park et al. ( 2001 ). However, milling and grinding induced starch damage (Lamberts et al. 2007 ). Degradation of starch molecules lowered the reassociation of amylose and amylopectin when cooling. Thus low setback viscosity, which indicated a low rate of starch retrogradation, was noticed in high DOM rice.

Nutrients of black rice

Prominent nutrients of black rice are shown in Fig.  3 a. The protein content of black rice decreased from 9.58 to 6.67 g/100 g during milling for 100 s. Milling for 10 s caused considerable reduction of protein ( p  < 0.05), and afterward, it was constantly diminished with consecutive milling. Black rice contained high ash content of 2.14 g/100 g. It significantly reduced ( p  < 0.05) to 1.43 g/100 g when milling for 10 s. Trivial changes was shown during milling 30–100 s. Ultimately the remained content was 0.37 g/100 g at the end of milling. Similarly fat content in black rice (4.63 g/100 g) decreased significantly ( p  < 0.05) to 2.61 g/100 g at 10 s because bran layers were removed. Fat content gradually decreased with successive milling. At 100 s milling, well-milled black rice was obtained with a fat content of 0.31 g/100 g.

Effect of milling on a nutrients and b resistant starch content and dietary fiber content of black rice. In a group, bars with different letters were significantly different at p  < 0.05 (n = 3)

Milling removes nutrients from rice kernels, but losses are varied. Protein, minerals, and fat were not consistently allocated in the black rice kernels. The effect of milling on protein content is less than fat content because a large amount of protein is in the endosperm. A similar finding on protein distribution was reported by Lamberts et al. ( 2007 ) that most of the protein in long-grain brown rice (~ 84.2%) existed in endosperm (DOM > 9%). For black rice, endosperm was attained when they were milled for longer than 10 s, and protein content in endosperm was around 82% of the entire protein in rice kernel. Protein in black rice still locates densely in the bran layer; thus substantial loss of protein (1.44 g/100 g) was displayed when almost bran fraction was removed (milling 10 s or DOM ~ 6%).

For brown rice, ash content distributed most in bran fraction (61%), and they uniformly scattered in the middle and core endosperm (Lamberts et al. 2007 ). Quadratic and exponential equations were presented for the relationship between ash content and milling duration (Singh et al. 2000 ). Similarly, most of the ash content in black rice located in the bran fraction, and the remainder was in the endosperm. But it steadily reduced with milling time. Hence the relationship between ash content and milling duration varied among rice cultivars with different grain compositions and kernel shapes. High ash loss was noticed in a cultivar with a low length–width ratio (Singh et al. 2000 ). Moreover, losses of specific minerals (iron, zinc, and selenium) during milling differed in their locations in grain kernels (Prom-u-thai et al. 2007 ; Liang et al. 2008 ; Liu et al. 2009 ).

Fat in black rice is largely located in the bran layer (> 44%), and it decreased distinctly when bran fraction was removed. This was consistent with findings in studies done by Chen and Siebenmorgen ( 1997 ) and Ha et al. ( 2006 ), who reported a reduction of total fat content, surface lipid content, and neutraceutical lipid of brown rice with DOM.

Resistant starch and dietary fiber of black rice

From Fig.  3 b, the resistant starch content of black rice (6.30 g/100 g) did not significantly change when milling for 10 s (11.79 g/100 g) ( p ≥  0.05), but it increased when milling for 100 s (16.66 g/100 g) ( p  <  0.05 ). However, dietary fiber of black rice (5.73 g/100 g) notably reduced ( p  < 0.05) to 4.27 and 0.79 g/100 g when milling for 10 s and 100 s, respectively.

Although an obvious trend was not exhibited, resistant starch slightly increased with DOM. This might be due to more starch fractions in high DOM rice. Dietary fiber mostly located in bran fraction, and it reduced with DOM. This agreed with Lai et al. ( 2006 ), who reported contraction of total dietary content in brown rice included pectic substance, hemicellulose, and cellulose with DOM. The total dietary fiber of brown rice was more than that of milled rice around 3–4%. However, milling of black rice for 10 s (DOM ~ 6%) did not remove much bran fraction, and dietary fiber still existed almost 75% of total dietary fiber.

Rice with the bran layer is not simply digested. Brown rice is classified as low and medium GI food, whereas milled rice was high GI food. Glucose released during digestion of brown rice was lower than those of milled rice (Leonora et al. 2006 ) because brown rice had more dietary fiber, fat, phytic acid, and polyphenols. Additionally, bran layers inhibited water and acid absorption and gastric juice diffusion during simulated gastric digestion; thus breakage, solubility, and digestibility of rice kernels was hindered (Kong et al. 2011 ).

Antioxidant properties of black rice

Black fragrant rice (Hom Nil cultivar) was claimed as a good source of antioxidants. It contained total phenolic and anthocyanin content of 186.20 mg GAE/100 g and 24.55 mg/100 g, respectively (Fig.  4 ). Phenolic content sharply reduced to 127.82 mg GAE/100 g when milling for 10 s ( p  < 0.05), and then it gradually decreased to 61.01 mg GAE/100 g at 100 s milling. A similar pattern was observed in changes in anthocyanin content during milling. Anthocyanin in raw black rice suddenly decreased to 7.46 mg/100 g at 10 s milling ( p  < 0.05) before petty alterations were noticed during 30–60 s. Lastly, milling for 100 s completely removed anthocyanin pigments from black rice kernel. Antioxidants were eliminated during milling. Therefore, DPPH scavenging activity of raw black rice (227 mg AAE/100 g) indubitably reduced to 175 mg AAE/100 g when milling only 10 s ( p  < 0.05). Additional milling (30–100 s) caused a slight decline of DPPH activity to 118 mg AAE/100 g.

Effect of milling on phenolic content (mg GAE/100 g), anthocyanin content (mg/100 g) and DPPH scavenging acivity (mg AAE/100 g) of black rice. In a group, bars with different letters were significantly different at p  < 0.05 (n = 3)

Black rice contains beneficial antioxidants comprised of polyphenolics, flavonoids, vitamin E, phytic acid, and γ-oryzanol. At 85% degree of milling, Kong and Lee ( 2010 ) found a large amount of free polyphenols and flavonoids in the bran fraction of black rice, and a small amount was in the endosperm. For Hom Nil black rice, a moderate amount of phenolic compounds (58.38 mg GAE/100 g or 31%) was eliminated after milling for 10 s (DOM ~ 6%). When all bran (calculated as the difference in contents of black rice and rice milled for 30 s or DOM ~ 12%) was entirely removed, phenolic compounds lost around 102.17 mg GAE/100 g or 55%. Other researchers (Zhou et al. 2004 ; Walter et al. 2011 ) reported a relatively higher amount of phenolic compounds in the light brown pericarp (70–90%) and black pericarp (92–97%). Variations were due to cultivar, particularly phenolic compounds contained in rice kernels, degree of milling, and extraction methods used to determine total phenolic content.

Almost 85% of anthocyanin, which was one of the flavonoids, was in bran layers of black rice (Hu et al. 2003 ). In this study, milling at 10 s (DOM ~ 6%) did not remove all bran layer, and consequently, 30% of total anthocyanin remained in rice kernels.

Antioxidant activity reduced with decreasing in antioxidants after milling. Milling of black grains affected antioxidant activity similar to the effect on polyphenols. It reduced around 88% when black rice was polished (Walter et al. 2011 ). In this study, only 35% decline of antioxidant activity was perceived when all bran (milling for 30 s or DOM ~ 12%) was confidently removed. Black rice milled at 10 s (DOM ~ 6%) still had 77% of the antioxidant activity of black rice.

Sensory quality of cooked black rice

Black rice samples with different degrees of milling were cooked, and sensory qualities evaluated by the panelists are presented in Table ​ Table2. 2 . Overall, acceptability and color scores of raw black rice were not significantly different ( p  ≥ 0.05) from those of black rice milled for 10–100 s. Appearance scores increased with milling time with obvious notice at 30 s (DOM ~ 12%) of milling ( p  < 0.05). However, panelists apparently preferred cooked rice milled for 10 s (DOM ~ 6%) when odor, flavor, and texture were inquired.

Effect of milling on sensory qualities of black rice

All values are means ± standard deviation (n = 30)

The outer seed coat of raw rice caused unpleasant flavor and texture. Removing a small portion of the bran layer produced cooked rice without strong bran flavor and tough texture. Panelists preferred mostly on well-milled and lightly milled rice. Park et al. ( 2001 ) described the detail of changes of sensorial qualities with DOM. Panelists detected decreasing of color, grain integrity, puffed corn flavor, raw rice flavor, wet cardboard flavor, hay-like flavor and bitterness of cooked rice, whereas glossiness, plumpness, sweetness increased. For texture, agglomeration, adhesiveness, cohesiveness, inner moisture, tooth packing of cooked rice increased, but hardness and chewiness decreased.

Improving odor, flavor, and texture acceptance of cooked black rice when milling at 10 s (DOM ~ 6%) concurrently perceived with reducing of instrumental textural hardness and fat content.

Milling definitely diminishes healthful compounds in black rice; however, losses depend on their locations in grain kernels. Milling at 10 s (DOM ~ 6%) did not remove all bran fractions. Small losses of protein (15%) and dietary fiber (25%) were noticed, whereas evident losses of ash (33%), fat (44%), phenolic compounds (31%) and anthocyanin (70%) were observed. In contrast, milling at 10 s appreciably improved the cooking qualities of black rice by reducing cooking time (~ 7 min) and increasing water uptake ratio and volume expansion ratio. Additionally, cooked black rice had impressively softer texture. Panelists preferred odor, flavor, and texture of cooked lightly milled black rice to cooked unmilled black rice.

Acknowledgements

This work was granted from Srinakharinwirot University (Project No. 114/2557). The assistance from Professor Athapol Noomhorm and the Asian Institute of Technology, Thailand, is gratefully acknowledged.

Publisher's Note

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• Published: 14 October 2022

Two decades of rice research in Indonesia and the Philippines: A systematic review and research agenda for the social sciences

• Ginbert P. Cuaton   ORCID: orcid.org/0000-0002-5902-3173 1 &
• Laurence L. Delina   ORCID: orcid.org/0000-0001-8637-4609 1  

Humanities and Social Sciences Communications volume  9 , Article number:  372 ( 2022 ) Cite this article

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While rice studies are abundant, they usually focus on macro-level rice production and yield data, genetic diversity, cultivar varieties, and agrotechnological innovations. Moreover, many of these studies are either region-wide or concentrated on countries in the Global North. Collecting, synthesizing, and analyzing the different themes and topic areas in rice research since the beginning of the 21st century, especially in the Global South, remain unaddressed areas. This study contributes to filling these research lacunae by systematically reviewing 2243 rice-related articles cumulatively written by more than 6000 authors and published in over 900 scientific journals. Using the PRISMA 2020 guidelines, this study screened and retrieved articles published from 2001 to 2021 on the various topics and questions surrounding rice research in Indonesia and the Philippines—two rice-producing and -consuming, as well as emerging economies in Southeast Asia. Using a combination of bibliometrics and quantitative content analysis, this paper discusses the productive, relevant, and influential rice scholars; key institutions, including affiliations, countries, and funders; important articles and journals; and knowledge hotspots in these two countries. It also discusses the contributions of the social sciences, highlights key gaps, and provides a research agenda across six interdisciplinary areas for future studies. This paper mainly argues that an interdisciplinary and comparative inquiry of potentially novel topic areas and research questions could deepen and widen scholarly interests beyond conventional natural science-informed rice research in Indonesia and the Philippines. Finally, this paper serves other researchers in their review of other crops in broader global agriculture.

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Introduction

Rice feeds the majority of the world’s population and employs millions, especially in developing countries in the Global South (Muthayya et al., 2014 ). Rice consumption has increased globally over the last decade. Statista data show that, in the cropping year 2020/2021, the world population consumed about 504.3 million metric tons of rice, increasing from 437.18 million metric tons in 2008/2009 (Shabandeh, 2021 ). These data highlight the crop’s global contribution and importance, especially in realizing the Sustainable Development Goals (SDGs), the blueprint for global prosperity (Gil et al., 2019 ). The SDGs call for systems transformation, including in agriculture, guided by the principles of sustainability and equity, driven by the leave-no-one-behind aphorism, to address the root causes of perennial poverty and chronic hunger.

Pathologist M. B. Waite ( 1915 ) pointed out that the apparent indicator of progress in modern agriculture is the application of scientific research and the subsequent modification and improvement of farming systems based on those research. For example, the Green Revolution resulted in increased agricultural production in developing countries due to the transfer of agrotechnological innovations from countries in the Global North to countries in the Global South. Although, we acknowledge that this project came with a cost (Glaeser, 2010 ; Pielke and Linnér, 2019 ; Pingali, 2012 ).

Regional rice studies have proliferated in Europe (Ferrero and Nguyen, 2004 ; Kraehmer et al., 2017 ), the Americas (Singh et al., 2017 ), Africa (Zenna et al., 2017 ), the Asia Pacific (Papademetriou et al., 2000 ), and South Asia (John and Fielding, 2014 ). Country studies on rice production have also emerged in Australia (Bajwa and Chauhan, 2017 ), China (Peng et al., 2009 ), and India (Mahajan et al., 2017 ). Scholars have also systematically reviewed rice’s phytochemical and therapeutic potentials (Sen et al., 2020 ), quality improvements (Prom-u-thai and Rerkasem, 2020 ), and its role in alleviating the effects of chronic diseases and malnutrition (Dipti et al., 2012 ).

These extant studies, however, are limited on at least three fronts. First, their foci were on rice production, yield, and operational practices and challenges at the macro level. Second, there have been zero attempts at synthesizing this corpus since the 21st century. Third, there are also no attempts at examining the various rice research areas that scholars, institutions, and countries need to focus on, especially in developing country contexts, and their nexuses with the social sciences. This paper addresses these gaps by unpacking and synthesizing multiple rice studies conducted in the emerging Southeast Asian economies of Indonesia and the Philippines from 2001 to 2021. A focus on these developing countries matters since they are home to over 35 million rice farmers (IRRI, 2013 ).

We conducted our review from the Scopus database, using a combination of bibliometric and quantitative content analyses. Section “Results and discussions” reports our results, where we discuss (1) the most relevant and influential rice scholars and their collaboration networks; (2) the most rice research productive institutions, including author affiliations, their countries, and their research funders; and (3) the most significant articles and journals in rice research. This section also identifies 11 topic areas belonging to four major themes of importance for rice research in the two countries. Section “Contributions from and research agenda for the social sciences” provides a research agenda, where we identify and discuss the contributions of our review in terms of future work. Despite the preponderance of rice research in the last two decades and more in Indonesia and the Philippines, contributions from the social sciences remain marginal. Thus, in the section “Conclusion”, we conclude that emphasis is needed on expanding and maximizing the contributions of social scientists given the many opportunities available, especially for conducting interdisciplinary and comparative rice research in these Southeast Asian countries.

Review methods and analytical approach

We used bibliometric and quantitative content analyses to systematically categorize and analyze more than two decades of academic literature on rice in Indonesia and the Philippines. Bibliometric methods, also known as bibliometrics, have grown to be influential in evaluating various research fields and topic areas. Bibliometrics mushroomed because of the increasing availability of online databases and new or improved analysis software (Dominko and Verbič, 2019 ). Bibliometrics quantitatively and statistically analyze research articles using their bibliographic data, such as authors, affiliations, funders, abstracts, titles, and keywords. These data are analyzed to identify and assess the development, maturity, research hotspots, knowledge gaps, and research trends (Aria and Cuccurullo, 2017 ). For example, bibliometrics have been used in reviewing hydrological modeling methods (Addor and Melsen, 2019 ), business and public administration (Cuccurullo et al., 2016 ), and animals’ cognition and behavior (Aria et al., 2021 ).

This review article used bibliometrix , a machine-assisted program that offers multiple options and flexibility to map the literature comprehensively (Aria and Cuccurullo, 2017 ). We run this program using R Studio version 4.1.2 (2021-11-01; “Bird Hippie”) for its source code readability, understandability, and easy-to-do computer programming (Cuaton et al., 2021 ). We used bibliometrix in three critical analytical phases: (a) importing and converting data to R format, (b) identifying our dataset’s collaboration networks and intellectual and conceptual structures, and (c) processing, presenting, and analyzing our dataset. Bibliometrix, however, is unable to produce specific data that we want to highlight in this paper; examples of these are our coding criteria on interdisciplinarity and author gender, where such information was not captured in the articles’ bibliographic data in Scopus. We addressed these issues by conducting a quantitative content analysis (QCA) of our dataset. QCA is a method to record, categorize, and analyze textual, visual, or aural materials (Coe and Scacco, 2017 ). QCA has been applied in other reviews, such as in energy research development in the social sciences (Sovacool, 2014 ), the concepts of energy justice (Jenkins et al., 2021 ), and in examining agricultural issues in Botswana (Oladele and Boago, 2011 ) and Bangladesh (Khatun et al., 2021 ).

Search strategies

We constructed our dataset from the Scopus database, which we accessed via our institution’s online library on 14 November 2021. Scopus is a scientific database established in 2004 and owned by Elsevier Ltd. (Elsevier, 2021 ). We excluded other databases, such as Google Scholar, ScienceDirect, Web of Science, and EBSCO, suggesting one potential bias in our review (Waltman, 2016 ; Zupic and Čater, 2015 ). Our decision to exclusively use Scopus arises from two main reasons. First, the database has broader coverage than others, including the abovementioned (Falagas et al., 2008 ). Scopus includes new and emerging journals published in developing countries like Indonesia and the Philippines, our focus countries. Second, Scopus has a user-friendly interface and its search options allow researchers to flexibly explore its universe of indexed articles based on authors, institutions, titles, abstracts, keywords, and references (Donthu et al., 2021 ).

We followed the PRISMA 2020 Guideline (Preferred Reporting Items for Systematic reviews and Meta-Analyses) (Page et al., 2021 ) in our search for potential rice-related studies in Indonesia and the Philippines (see Fig. 1 ). We used the initial search string: “rice” AND “Indonesia*” OR “Philippine*” (asterisk or “*” was used as a wildcard search strategy) and limited the year coverage from 2001 to 2021. Our first round of searches resulted in 3846 documents (results as of 14 November 2021). We filtered these documents by including only peer-reviewed, full-text English articles on rice. We did not include any documents from the grey literature (e.g., news items, press releases, government or corporate reports), and other document types indexed in Scopus such as reviews, books, conference papers, errata, comments, editorials, and short reports.

Our initial result of 3846 documents (results as of 14 November 2021) was filtered by including only peer-reviewed, full-text English articles on rice, resulting in 2243 eligible documents.

We also excluded articles with irrelevant keywords by using the following combined queries:

This resulted in 2243 eligible documents. We downloaded these documents as raw files in BibTex format and imported them to Biblioshiny , a web interface in Bibliometrix, where they were further filtered. Our verified final dataset comprises 2243 full-text English articles cumulatively written by 6893 authors and published across 909 journals (see Table 1 ).

Structure and analytical approach

We examined the authors’ profiles based on their gender, relevance in the study, and global impact. For gender, we coded them into ‘man,’ ‘woman,’ and ‘undetermined’ because some did not put enough information that helps in gender identification. We identified their gender by counter-checking their Scopus profiles to their verified accounts in Google Scholar, ResearchGate, Publons/Web of Science, or institutional profiles. We measured the authors’ relevance and impact against their (a) productivity, (b) citations, and (c) H-indices. We acknowledge, however, that some Filipino and Indonesian scholars, whose papers may not be indexed in Scopus, could also be prolific based on different parameters, but we excluded them. We proceeded to map the collaboration networks of these authors to identify “who works with whom on what.” A collaboration network illustrates nodes (circle shape) as authors and links (connecting lines) as co-authorships (Glänzel and Schubert, 2005 ).

Institutions, countries, funders

Following Sovacool ( 2014 ), we categorized the authors’ institutions into four: (1) University and research included authors who are researchers, instructors/lecturers/professors, other academic faculty from various non-university research think tanks, institutes, and national and local research centers; (2) Government consisted country or state departments, bureaus, ministries, and other government regulatory bodies; (3) Interest groups and NGOs included intergovernmental bodies, such as the United Nations Food and Agriculture Office (FAO) and international organizations like the International Rice Research Institute (IRRI) and Oxfam; and (4) Banking and finance encompassed players from the finance sector, including multilateral development banks such as the Asian Development Bank (ADB), World Bank, and the International Fund for Agricultural Development (IFAD). After coding and categorizing, we analyzed the authors’ institutional collaboration networks.

We identified the country’s productivity and coded them by global region based on their geographical location: (a) Asia, (b) Australia, New Zealand, and South Pacific, (c) Europe, (d) North America, (e) South America, and (f) Africa. We did this to show how various countries have been researching rice in Indonesia and the Philippines since the 21st century.

We then constructed a country collaboration map as a visual macro-representation of countries working together on rice research using these data. Bibliometrix, however, measured the country’s productivity based on the corresponding authors’ affiliations. We, therefore, noted two critical points here. First, many corresponding authors may have multiple institutional affiliations. For example, one corresponding author may belong to more than two affiliations (e.g., a corresponding Filipino author may have concurrent institutional affiliations in Japan, Australia, and New Zealand). Second, the corresponding authors may not necessarily be nationals of that country. Note that the unit of analysis is based on the corresponding authors’ institutional affiliations at the time of publication and not on their country/ies of citizenship or nationality. Despite these, our findings still provide insight into the macro-level productivity of countries conducting rice research in Indonesia and the Philippines.

We analyzed the funders using Scopus’ in-house Analytics Tool and determined their relevance based on the number of articles mentioning them in the Funding source or Acknowledgment section in the paper. We categorized the funders into six: (1) government (e.g., ministries, departments, or regulatory agencies), (2) research (e.g., research councils, research centers, and national academies), (3) foundations and non-government organizations (NGOs), (4) universities, (5) private companies and corporations, and (6) intergovernmental organizations/IGOs, including multilateral development banks.

Articles and journals

In terms of interdisciplinarity, we coded the articles as (a) interdisciplinary, (b) disciplinary, or (c) unidentified by using the authors’ department or division affiliation/s as a proxy to determine their disciplinary training. We coded an article as interdisciplinary if it belonged to any of the three criteria: (1) it had an author that had training or belonged to a department/division in at least two conventional disciplines (e.g., agriculture, anthropology, sociology, biology); (2) it had an author that had a self-identified interdisciplinary department (e.g., interdisciplinary division, sustainability, agriculture economics, etc.); or (3) it had at least two authors with different disciplinary training or expertise (e.g., business and economics; crop science and political science, etc.). We coded an article as disciplinary if its author/s had only belonged to one conventional department/division affiliation (e.g., Division of Agriculture, Department of Economics, Division of Environmental Science, etc.). On the other hand, we coded an article as undetermined when the authors had only indicated the name of their institutions or did not indicate their departmental or division affiliations (e.g., only the University of the Philippines, IRRI, Universitas Gadja Mada, etc.).

We examined the articles based on their local relevance and global influence. Bibliometrix measured the articles’ relevance based on their “local citations” or citations received from the 2243 articles of our sample dataset. We did this to determine which papers are considered relevant by authors studying various areas of rice research in Indonesia and the Philippines. Global influence is measured based on the articles’ citations from the global research community or other scientific works beyond our sample dataset. We also conducted a co-citation analysis of the cited references. Co-citation is the frequency by which articles cite together two or more articles relevant to the topic areas of inquiry (Aria and Cuccurullo, 2017 ). Bibliometrix had identified some co-cited articles published before our timeline of interest (i.e., pre-2001) which provide scholars with a more profound understanding of rice research in the two countries.

On the other hand, Bibliometrix identified the most relevant journals based on the number of papers the journals had published and the local citations of the articles. These data guide readers and researchers on which journals to look for on rice studies in Indonesia and the Philippines.

Knowledge hotspots

Bibliometrix creates a thematic map that allows researchers to identify which study areas have been adequately explored and which areas need further investigation or re-investigation to identify knowledge hotspots and research gaps (Aria and Cuccurullo, 2017 ). Della Corte et al. ( 2019 , pp. 5–6) discussed the major themes in Bibliometrix in the following:

“Themes in the lower-right quadrant are the Basic Themes , characterized by high centrality and low density. These themes are considered essential for a research field and concerned with general topics across different research areas.

Themes in the upper-right quadrant are the Motor Themes , characterized by high centrality and density. Motor themes are considered developed and essential for the research field.

Themes in the upper-left quadrant are the highly developed and isolated themes or Niche Themes . They have well-developed internal links (high density) but unimportant external links, which could be interpreted as having limited importance for the field (low centrality).

Themes in the lower-left quadrant are known as Emerging or Declining Themes . They have low centrality and density, making them weakly developed and marginal.”

Contributions from and research agenda for the social sciences

As interdisciplinary environmental and social scientists, we also focused our review on the social studies of rice in the two countries. This section highlighted the gaps between the natural and the social sciences in rice research and advanced a research agenda for interdisciplinary and comparative social scientists.

Limitations

As in any systematic review, we acknowledge certain limitations to our work. We discuss four of these.

First, to keep a certain level of reliability, we focused only on peer-reviewed full-length research articles written in the English language and indexed in the Scopus database. Therefore, we may have excluded some relevant articles, including those written in Filipino, Indonesian, and other local or indigenous languages and published in local or international journals but are not indexed in Scopus. Our review also excluded conference papers, commentaries, book reviews, book chapters, conference reviews, data papers, errata, letters, notes, and non-academic publications like policy briefings, reports, and white papers.

Second, in our quantitative content analysis, we acknowledge the highly cis-heteronormative approach we used in coding the author’s gender as “man” or “woman.” We identified these genders from the names and pictures of the authors in their verified Scopus, Publons/ Web of Science, and institutional profiles. It is not our deliberate intention to neglect the varying genders of researchers and scientists beyond the traditional binary of man or woman.

Third, we recognize that our analysis cannot directly identify how much each funder provided as the unit of analysis in bibliometrix may depend on how prolific researchers were in publishing articles despite smaller funds. For instance, one research project supported by Funder A with US$1 million may have published only one article based on their project design or the funder's requirement. Since the authors published only one paper from this project, the data could show that Funder A only funded one research. Another research project, supported by Funder B, with only US$300,000 in funding, may have published more than five papers; therefore, more articles counted as funded by Funder B. This issue is not within the scope of our review.

Lastly, it should be noted that the future research works we discussed were highly influenced by our research interests and the general overview of the literature, and thus neither intend to cover nor aim to discuss the entire research topics that other scholars could study.

Despite these limitations, we strongly argue that our review provided relevant insights and proposed potentially novel topic areas and research questions for other scholars to explore, especially social scientists, in deepening and widening rice research in Indonesia and the Philippines. To end, we hope that researchers heed our call to conduct more interdisciplinary and comparative rice-related studies in these two emerging Southeast Asian countries.

Results and discussions

Our dataset comprises 2243 peer-reviewed journal articles cumulatively written by 6893 authors who cited around 80,000 cumulative references. The average annual publications from 2001 to 2013 were only 57 papers but elevated to hundreds beginning in 2014 (Fig. 2 ).

The average number of annual publications on rice research in Indonesia and the Philippines from 2001 to 2013 was only 57 papers but elevated to hundreds beginning in 2014.

Of the 159 authors, one had a duplicate profile; thus, we identified 158 authors publishing on rice studies; the majority (66%) are men. The top 50 most prolific scholars produced a little over 25% (567 articles) of the total articles. Australian ecologist Finbarr Horgan topped this list ( n  = 21), followed by Bas Bouman and Grant Singleton—each with 20 articles. The top 10 authors with the highest number of publications have affiliations with the IRRI, the University of the Philippines, the University of Gadjah Mada, and the Philippine Rice Research Institute (PhilRice). For the full list of prolific scholars with at least 10 articles published, see Supplementary Table 1 .

In terms of the authors with the most local citations, although Finbarr Horgan has the most documents, Johan Iskandar ( n  = 36 citations) from the Universitas Padjadjaran, who studies rice genetic diversity, is the most cited. Local citations refer to the citations received by authors from our sample dataset of 2243 articles. Muhidin Muhidin from the Universitas Halu Oleo and Ruhyat Partasasmita from the Universitas Padjadjaran, followed him with 30 and 28 local citations, respectively. Common to these three authors are their Biology background/expertise and interest in rice genetic diversity. To check the top 20 most locally cited scholars, refer to Supplementary Table 2 .

The H-index is the author-level measure of publications’ productivity and citation impacts (Hirsch, 2005 ). Bas Bouman (H-index = 18) leads the top 10 scholars among rice-related researchers in Indonesia and the Philippines. Yoshimichi Fukuta (H index = 13) and Shaobing Peng (H index = 13) followed him. These three authors are affiliated with or have collaborated with the IRRI. To check the top 10 scholars with the highest H-indices, refer to Supplementary Table 3 .

Figure 3 reveals the top 80 authors who collaborate across eight major clusters of rice research. The Red cluster shows Finbarr Horgan as the most prominent author with at least four significant collaborators in pest management, specifically on rice stemborers (Horgan et al., 2021 ), anthropods’ biodiversity in tropical rice ecosystems (Horgan et al., 2019 ), and virulence adaptations of rice leafhoppers (Horgan et al., 2018 ). In the Purple Cluster, Yoshimichi Fukuta has multiple publications with at least six collaborators in the study of rice blast (Ebitani et al., 2011 ; Kadeawi et al., 2021 ; Mizobuchi et al., 2014 ). In the Brown cluster, Bernard Canapi from the IRRI has collaborated with at least five scholars in the study of rice insect pest management (Cabasan et al., 2019 ; Halwart et al., 2014 ; Litsinger et al., 2011 ), farmers’ preference for rice traits (Laborte et al., 2015 ), and the drivers and consequences of genetic erosion in traditional rice agroecosystems in the Philippines (Zapico et al., 2020 ). The Gray cluster shows that Siti Herlinda has collaborated with at least four scholars to study anthropods in freshwater swamp rice fields (Hanif et al., 2020 ; Herlinda et al., 2020 ) and the benefits of biochar on rice growth and yield (Lakitan et al., 2018 ).

The authors’ collaboration networks show eight major clusters of rice research in Indonesia and the Philippines.

Institutions

Author affiliations.

In terms of institutional types, Fig. 4 shows that most rice researchers in Indonesia and the Philippines have affiliations with “University and research.” Figure 5 shows the top 20 institutions in terms of research productivity led by the IRRI, the University of the Philippines System, the PhilRice, the Institute Pertanian Bogor/IPB University, and the University of Gadja Mada. These 20 institutions produced 66% of the articles in our dataset.

The majority of rice researchers in Indonesia and the Philippines have affiliations with “University and research”.

The top 5 most productive institutions in terms of rice research in Indonesia and the Philippines are the IRRI, the University of the Philippines System, the PhilRice, the Institute Pertanian Bogor/IPB University, and the University of Gadja Mada.

Scholars affiliated with the IRRI have written the most papers (at least 19% or 358 articles) in our dataset. The range of topics covers both regional and country studies. Some regional examples include the drivers of consumer demand for packaged rice and rice fragrance in South and Southeast Asia (Bairagi et al., 2020 ; Bairagi, Gustafson et al., 2021 ). Country studies, for example, include an investigation of rice farming in Central Java, Indonesia (Connor et al., 2021 ), the cultural significance of heirloom rice in Ifugao in the Philippines (Bairagi, Custodio et al., 2021 ), and the distributional impacts of the 2019 Philippine rice tariffication policy (Balié and Valera, 2020 ).

The University of the Philippines System, with rice scholars affiliated with their campuses in Los Baños, Diliman, Mindanao, and Manila, produced the next largest number of papers (more than 200 or 10%) on topics about rice pests and parasites (Horgan et al., 2019 , 2021 ; Vu et al., 2018 ), weed control (Awan et al., 2014 , 2015 ; Fabro and Varca, 2012 ), and climate change impacts on rice farming (Alejo and Ella, 2019 ; Ducusin et al., 2019 ; Gata et al., 2020 ). Social studies of rice conducted by the University of the Philippines researchers include indigenous knowledge on climate risk management (Ruzol et al., 2020 , 2021 ), management options in extreme weather events (Lopez and Mendoza, 2004 ), agroecosystem change (Aguilar et al., 2021 ; Neyra-Cabatac et al., 2012 ), and the development and change over time of rice production landscapes (Santiago and Buot, 2018 ; Tekken et al., 2017 ).

PhilRice, a government-owned corporation under the Department of Agriculture (Official Gazette of the Philippines, 2021 ), is the third most prolific rice research-producing institution (122 papers) on topics ranging from nematodes or rice worms (Gergon et al., 2001 , 2002 ) and arthropods (invertebrates found in rice paddies) (Dominik et al., 2018 ), hybrid rice (Perez et al., 2008 ; Xu et al., 2002 ), alternate wetting-and-drying technology (Lampayan et al., 2015 ; Palis et al., 2017 ), and community development strategies on rice productions (Romanillos et al., 2016 ).

The IPB University, a public agrarian university in Bogor, Indonesia, investigates rice productivity and sustainability (Arif et al., 2012 ; Mucharam et al., 2020 ; Setiawan et al., 2013 ), irrigation (Nugroho et al., 2018 ; Panuju et al., 2013 ), extreme weather events such as drought (Dulbari et al., 2021 ), floods (Wakabayashi et al., 2021 ), and emerging social issues such as food security (Putra et al., 2020 ), land-use change (Chrisendo et al., 2020 ; Munajati et al., 2021 ), and sustainability (Mizuno et al., 2013 ). This university has 23 research centers, including those which focus on environmental research; agricultural and village development; engineering applications in tropical agriculture; Southeast Asian food and agriculture; and agrarian studies.

Universitas Gadja Maja in Yogyakarta, Indonesia, hosts 21 research centers, including its Agrotechnology Innovation Centre. It carries out research incubation and development activities, product commercialization, and integration of agriculture, animal husbandry, energy, and natural resources into a sustainable Science Techno Park. Some of their published studies focused on drought-tolerant rice cultivars (Salsinha et al., 2020 , 2021 ; Trijatmiko et al., 2014 ), farmers’ technical efficiency (Mulyani et al., 2020 ; Widyantari et al., 2018 , 2019 ), systems of rice intensification (Arif et al., 2015 ; Syahrawati et al., 2018 ), and climate change adaptation (Ansari et al., 2021 ).

In terms of institutional collaboration, the IRRI tops the list with at least eleven collaborators (Fig. 6 ), including the Japan International Center for Agricultural Sciences, the PhilRice, the University of the Philippines System, and the Indonesian Center for Rice Research.

The IRRI, as an international organization focused on many aspects of rice, is not surprising to have the greatest number of institutional collaborators ( n  = 11 institutions).

Rice studies’ authors are from at least 79 countries; the majority of them are working in Asia (79%), followed by Europe (13%) and North America (9%). At least 90% of rice scholars are in Indonesia, and more than 51% have affiliations in the Philippines, followed by Japan, the USA, and China. For the list of the top 20 most productive countries researching rice in Indonesia and the Philippines, see Supplementary Table 4 . Figure 7 shows a macro-level picture of how countries have collaborated on rice-related projects in Indonesia and the Philippines since 2001, suggesting that rice research in both countries has benefited from international partnerships.

A macro-level picture of how countries have collaborated on rice-related projects in Indonesia and the Philippines since 2001. It suggests that rice research in both countries has benefited from international partnerships.

Only around 47% (1050 studies) of our dataset acknowledged their funding sources, where most received financial support either from governments (45%), research (27%), or university funders (16%) (Fig. 8 ). To see the top 15 funders that supported at least 10 rice-related research projects in Indonesia and the Philippines from 2001 to 2021, refer to Supplementary Table 5 . Of over 150 rice research funders, Indonesia’s Ministry of Education, Culture, and Research (formerly the Ministry of Research and Technology) funded ~6% (62 out of 1050 studies). The Japan Society for the Promotion of Science and Japan’s Ministry of Education, Culture, Sports, Science and Technology came in as the second and third largest funders, respectively.

The majority of rice research projects in Indonesia and the Philippines were funded by governments (45%), research (27%), and university institutions (16%).

Half of all articles in the dataset were borne out of interdisciplinary collaboration. More than a quarter of the articles, however, were unidentified, showing an apparent undercount of the total number of disciplinary collaborations. Most of these collaborative pieces of work (~61%) belong to the natural science subject areas of agricultural and biological sciences; biochemistry, genetics, and molecular biology; and environmental science (see Table 2 ). Note that the cumulative number of articles in Table 2 is more than the total number of the sample dataset since an article may belong to multiple subject areas as indicated by its authors in Scopus. Less than 9% (354) of all papers were written by social scientists, highlighting their marginal contribution to rice research. The social studies of rice can increase our understanding of the many facets of rice production, including their socio-political, economic, and cultural aspects.

Our review shows that there are 10 major networks of rice research co-citations (Fig. 9 ). The papers by Bouman et al. ( 2005 ), Bouman et al. ( 2007 ), Bouman and Tuong ( 2001 ), and Tuong and Bouman ( 2003 ) were co-cited by scholars studying the relationship between water scarcity management vis-à-vis rice growth and yield (the purple cluster in Fig. 9 ). Papers by Yoshida et al. ( 2009 ), De Datta ( 1981 ), and Peng et al. ( 1999 ) were co-cited by scholars researching the genetic diversity, yield, and principles and practices of rice production in Indonesia (the red cluster in Fig. 9 ). Papers by Ou ( 1985 ), Mackill and Bonman ( 1992 ), Sambrook et al. ( 1989 ), Kauffman et al. ( 1973 ), Iyer and McCouch ( 2004 ), and Mew ( 1987 ) were considered essential references in studying rice diseases (blue cluster in Fig. 9 ). The top-cited article on rice research in Indonesia and the Philippines, based on their overall global citations, is a study on water-efficient and water-saving irrigation (Belder et al., 2004 ). This study detailed alternative options for typical water management in lowland rice cultivation, where fields are continuously submerged, hence requiring a continuous large amount of water supply (Belder et al., 2004 ). Global citations refer to the citations received by the articles within and beyond our sample dataset of 2243 articles. To see the top 10 most globally cited articles on rice research in Indonesia and the Philippines, refer to Supplementary Table 6 .

There are 10 major networks of rice research co-citations in Indonesia and the Philippines.

The journal Biodiversitas: Journal of Biological Diversity published the most number of papers on rice research in the two countries. Biodiversitas publishes papers “dealing with all biodiversity aspects of plants, animals, and microbes at the level of gene, species, ecosystem, and ethnobiology” (Biodiversitas, 2021 ). Following its indexing in Scopus in 2014, Biodiversitas has increasingly published rice studies, most of which were authored by Indonesian researchers. To see the top 10 most relevant journals for rice research in Indonesia and the Philippines based on the number of documents published since 2001, refer to Supplementary Table 7 .

Based on their local citations, the journals Field Crops Research , Theoretical & Applied Genetics , and Science are the most relevant. Field Crops Research focuses on crop ecology, crop physiology, and agronomy of field crops for food, fiber, feed, medicine, and biofuel. Theoretical and Applied Genetics publishes original research and review articles in all critical areas of modern plant genetics, plant genomics, and plant biotechnology. Science is the peer-reviewed academic journal of the American Association for the Advancement of Science and one of the world’s top academic journals. To see the top 30 most relevant journals for rice research in Indonesia and the Philippines based on the number of local citations, refer to Supplementary Table 8 .

The most used keywords found in 2243 rice research papers published between 2001 and 2021 in Indonesia and the Philippines are food security, climate change, drought, agriculture, irrigation, genetic diversity, sustainability, technical efficiency, and production (Fig. 10 ). We found 11 clusters across four significant themes of rice research in these countries (Fig. 11 ).

The most used keywords found in 2243 rice research papers published between 2001 and 2021 in Indonesia and the Philippines are food security, climate change, drought, agriculture, irrigation, genetic diversity, sustainability, technical efficiency, and production.

There are four major themes composed of 11 clusters of rice research in Indonesia and the Philippines since 2001.

Basic themes

We identified four major clusters under ‘basic themes’ (refer to Fig. 11 ):

The Red Cluster on studies in the Philippines related to rice yield and productivity, drought, nitrogen, the Green Revolution, and the use and potential of biomass;

The Blue Cluster on studies in Indonesia related to food security, climate change, agriculture, upland rice, irrigation, technical efficiency, and sustainability vis-à-vis rice production;

The Green Cluster on rice genetic diversity, bacterial blight diseases, resistant rice genes, aerobic rice, and brown planthoppers; and

The Gray Cluster on the nutritional aspects of rice, including studies on biofortified rice cultivars.

Agriculture suffers from climate change impacts and weather extremes. Rice researchers in Indonesia and the Philippines are identifying drought-tolerant rice cultivars that can produce high yields in abiotic stress-prone environments (Afa et al., 2018 ; Niones et al., 2021 ). These hybrid cultivars are vital for increasing rice productivity, meeting production demand, and feeding the growing Filipino and Indonesian populations (Kumar et al., 2021 ; Lapuz et al., 2019 ). Researchers have also looked at alternative nutrient and water management strategies that farmers can use, especially those in rainfed lowland areas during drought (Banayo, Bueno et al., 2018 ; Banayo, Haefele et al., 2018 ). There were also studies on the socio-cultural dynamics under which farmers adapt to droughts, such as how past experiences of hazards influence farmers’ perceptions of and actions toward drought (Manalo et al., 2020 ).

Motor themes

We identified three significant clusters of ‘motor themes’ (refer to Fig. 11 ):

The Pink Cluster on yield loss and integrated pest management of rice fields;

The Blue-Green Cluster on biodiversity, ecosystem services, remote sensing, and water productivity; and

The Orange Cluster on the antioxidant properties of rice bran and black rice.

In both countries, pests, including weeds (Awan et al., 2014 , 2015 ), insects (Horgan et al., 2018 , 2021 ), and rodents (Singleton, 2011 ; Singleton et al., 2005 , 2010 ), have significant impacts on yield loss in rice production and human health. To address these, many farmers have embraced chemical-heavy pest management practices to prevent yield loss and increase economic benefits. Pesticides began their use in Indonesia and the Philippines and rapidly expanded from the 1970s to the 1980s (Resosudarmo, 2012 ; Templeton and Jamora, 2010 ). However, indiscriminate use of pesticides caused an ecological imbalance that exacerbated pest problems (Templeton and Jamora, 2010 ) and contributed to farmers’ acute and chronic health risks (Antle and Pingali, 1994 ; Pingali and Roger, 1995 ).

Integrated pest management was introduced, applied, and studied in both countries to address these issues. This approach combines multiple compatible pest control strategies to protect crops, reduce pesticide use, and decrease farming costs (Gott and Coyle, 2019 ). For example, Indonesia’s 1989 National Integrated Pest Management Program trained hundreds of thousands of farmers and agricultural officials about its principles, techniques, and strategies (Resosudarmo, 2012 ). In the Philippines, the government of then-President Fidel V. Ramos (1992–1996) prohibited using hazardous pesticides and instituted a “multi-pronged approach to the judicious use of pesticides” (Templeton and Jamora, 2010 , p. 1). President Ramos’ suite of policies included deploying Integrated Pest Management “as a national program to encourage a more ecologically sound approach to pest control” (Templeton and Jamora, 2010 , p. 1). This pesticide policy package benefited the Philippine government in terms of private health costs avoided (Templeton and Jamora, 2010 ).

To address weed problems, farmers traditionally use manual weeding, a labor-intensive practice. However, as labor costs for manual weeding increased, herbicide use became economically attractive to farmers (Beltran et al., 2012 ). Herbicide experiments were made to address common rice weeds including barnyard grass ( Echinochloa crus-galli ) (Juliano et al., 2010 ), crowfoot grass ( Dactyloctenium aegyptium ) (Chauhan, 2011 ), three-lobe morning glory ( Ipomoea triloba ) (Chauhan and Abugho, 2012 ), and jungle rice ( Echinochloa colona ) (Chauhan and Johnson, 2009 ). Knowledge gained from these experiments contributed to the development of integrated weed management strategies.

Yet, many factors come into play when farmers decide to use herbicides. Beltran et al. ( 2013 ) reported that farmers’ age, household size, and irrigation use are significant determinants of adopting herbicides as an alternative to manual weeding. Beltran et al. ( 2013 ) further showed that economic variables, like the price of the herbicide, household income, and access to credit, determined farmers’ level of herbicide use (Beltran et al., 2013 ). Their study highlights the complex decision-making process and competing factors affecting weed management in the Philippines.

Apart from weeds, insects, like brown planthoppers ( Nilaparvata lugens ) and green leafhoppers ( Cicadella viridis ) and their accompanying diseases, affect rice production. In Java, Indonesia, Triwidodo ( 2020 ) reported a significant influence between the insecticide use scheme and the brown planthopper ( Nilaparvata lugens ) attack rates in rice fields. Brown planthopper attacks increased depending on the frequency of pesticide application, their varieties, and volume (Triwidodo, 2020 ). In the Philippines, Kim and colleagues ( 2019 ) developed a rice tungro epidemiological model for a seasonal disaster risk management approach to insect infestation.

Some social studies of integrated pest management included those that looked at the cultural practices that mitigate insect pest losses (Litsinger et al., 2011 ) and farmers’ knowledge, attitudes, and methods to manage rodent populations (Stuart et al., 2011 ). Other social scientists evaluated the value of amphibians as pest controls, bio-monitors for pest-related health outcomes, and local food and income sources (Propper et al., 2020 ).

Niche themes

We identified two ‘niche themes’ consisting of studies related to (a) temperature change and (b) organic rice production (refer to Fig. 11 ). Temperature change significantly affects rice farming. In the Philippines, Stuecker et al. ( 2018 ) found that El Niño-induced soil moisture variations negatively affected rice production from 1987–2016. According to one experiment, high night temperature stress also affect rice yield and metabolic profiles (Schaarschmidt et al., 2020 ). In Indonesia, a study suggests that introducing additional elements, such as Azolla, fish, and ducks, into the rice farming system may enhance rice farmers’ capacity to adapt to climate change (Khumairoh et al., 2018 ). Another study produced a rainfall model for Malang Regency using Spatial Vector Autoregression. This model is essential as rainfall pattern largely determines the cropping pattern of rice and other crops in Indonesia (Sumarminingsih, 2021 ).

Studies on organic rice farming in the Philippines include resource-poor farmers’ transition from technological to ecological rice farming (Carpenter, 2003 ) and the benefits of organic agriculture in rice agroecosystems (Mendoza, 2004 ). Other studies on organic rice focused on its impacts on agricultural development (Broad and Cavanagh, 2012 ) and climate resilience (Heckelman et al., 2018 ). In Indonesia, Martawijaya and Montgomery ( 2004 ) found that the local demand for organic rice produced in East Java was insufficient to generate revenue enough to cover its production costs. In West Java, Komatsuzaki and Syuaib ( 2010 ) found that organic rice farming fields have higher soil carbon storage capacity than fields where rice is grown conventionally. In Bali, farmers found it challenging to adopt organic rice farming vis-à-vis the complex and often contradictory and contested administration of the Subaks (MacRae and Arthawiguna, 2011 ) and the challenges they have to confront in marketing their produce (Macrae, 2011 ).

Emerging or declining themes

We identified two clusters of ‘emerging/declining themes’ or areas of rice research that are weakly developed and marginal (refer to Fig. 11 ). The Purple Cluster (emerging) studies rice straw, rice husk, methane, and rice cultivation, while the Light Blue Cluster (declining) pertains to local rice research.

In this section, we present and discuss the contributions of the social sciences, highlight key gaps, and provide a research agenda across six interdisciplinary areas for future studies. In Table 3 , we summarized the various topic areas that other scholars could focus on in their future studies of rice in Indonesia and the Philippines.

Economic, political, and policy studies

Political scientist Ernest A. Engelbert ( 1953 ) was one of the earliest scholars to summarize the importance of studying agricultural economics, politics, and policies. Engelbert ( 1953 ) identified three primary reasons scholars and laypeople alike need to understand the nature of political processes in agriculture. First, the rapid change and highly contested political environment where agriculture operates often places agriculture last on national policy agenda. Second, the formulation of agricultural policies intersects with contemporary national and economic contexts by which these policies revolve. Third, understanding the political processes around agriculture can help avoid political pressures and machinations aimed at undermining agricultural development.

Politics play a crucial role in better understanding rice- and agriculture-related policies, their evolution, dynamics, challenges, developments, and futures. Grant ( 2012 , p. 271) aptly asks, “Who benefits [from government policies, regulations, and programs]?” . Knowing, understanding, and answering this question is crucial since policymaking is a highly contested process influenced and negotiated not only by farmers and decision-makers but also by other interest groups, such as people’s organizations and non-government organizations. On the other hand, understanding macro- and micro-economic government arrangements come hand-in-hand in analyzing how policies impact farmers and consumers. Using tariffs as an example, Laiprakobsup ( 2014 , p. 381) noted the effects of government interventions in the agrarian market:

“… when the government implements consumer subsidy programs by requiring the farmers to sell their commodities at a cheaper price, it transfers the farmers’ incomes that they were supposed to earn to the consumers. Moreover, the government transfers tax burdens to the farmers via export taxes in that the agricultural industry is likely to purchase the farmers’ commodities as cheaply as possible in order to make up for its cost.”

The two countries have compelling economic, political, and policy-oriented rice studies. Some examples of this type of research in the Philippines are the following. Intal and Garcia ( 2005 ) argued that the price of rice had been a significant determinant in election results since the 1950s. Fang ( 2016 ) analyzed how the Philippines’ colonial history bolstered an oligarchy system, where landed elite politicians and patronage politics perpetuated corruption to the detriment of rice farmers. Balié and Valera ( 2020 ) examined rice trade policy reforms’ domestic and international impacts. San Juan ( 2021 ) contends that the 2019 Rice Tariffication Law of the Philippines only encouraged the country to rely on imports and failed to make the local rice industry more competitive.

In Indonesia, some political studies on rice production are the following. Putra et al. ( 2020 ) analyzed how urbanization affected food consumption, food composition, and farming performance. Noviar et al. ( 2020 ) provided evidence that households in the rice sub-sector have achieved an insufficient level of commercialization in their rice production. Rustiadi et al. ( 2021 ) investigated the impacts of land incursions over traditionally rice farming regions due to Jakarta’s continuous expansion. Satriawan and Shrestha ( 2018 ) evaluated how Indonesian households participated in the Raskin program, a nationwide rice price subsidy scheme for the poor. Misdawita et al. ( 2019 ) formulated a social accounting matrix and used a microsimulation approach to assess the impacts of food prices on the Indonesian economy.

Future work

Social science researchers could further explore and compare the local, regional, and national similarities and differences of the abovementioned issues or conduct novel research related to land-use change, land management, urbanization, food and agricultural policies, trade policies, irrigation governance, and price dynamics. Comparative social studies of rice could also lead to meaningful results. As social policy scholar Linda Hantrais noted:

“Comparisons can lead to fresh, exciting insights and a deeper understanding of issues that are of central concern in different countries. They can lead to the identification of gaps in knowledge and may point to possible directions that could be followed and about which the researcher may not previously have been aware. They may also help to sharpen the focus of analysis of the subject under study by suggesting new perspectives.” (Hantrais, 1995 , p. n/a).

Sociological, anthropological, and cultural studies

Biologists dominated agricultural research until the mid-1960s (Doorman, 1991 ). Agriculture, in other words, was no social scientist’s business. However, this situation gradually changed when governments and scholars realized the long-term impacts of the Green Revolution from the 1950s to the 1980s, which underscores that the development, transfer, and adoption of new agrotechnology, especially in developing countries, is driven not only by techno-biological factors but also by the socio-economic, political, and cultural realities under which the farmers operate. Since then, sociologists, anthropologists, and cultural scholars have become indispensable in answering the “how”, “what”, and “why” agrarian communities follow, adopt, utilize, or, in some cases, prefer local/traditional production technologies over the technological and scientific innovations developed by engineers, biologists, geneticists, and agriculturists. Nyle C. Brady, a soil scientist and the former Director-General of the IRRI pointed out:

“… we increasingly recognize that factors relating directly to the farmer, his family, and his community must be considered if the full effects of agricultural research are to be realized. This recognition has come partly from the participation of anthropologists and other social scientists in interdisciplinary teams … during the past few years.” (IRRI, 1982 ).

Since the late 19th century, many rice studies have tried to answer the roles of social scientists in agricultural research. Social sciences have contributed to agricultural research in many ways, especially regarding technology adoption by farmers (DeWalt, 1985 ; Doorman, 1990 ). Doorman ( 1991 , p. 4) synthesized these studies and offered seven roles for sociologists and anthropologists in agricultural research as follows:

“Accommodator of new technology, ex-post and ex-ante evaluator of the impact of new technology, an indicator of the needs for new technology, translator of farmer’s perceptions, broker-sensitizer, adviser in on-farm research, and trainer of team members from other disciplines.”

Social studies of rice are especially critical in Indonesia and the Philippines—home to hundreds of Indigenous cultural communities and Indigenous peoples (Asian Development Bank, 2002 ; UNDP Philippines, 2010 ). Regardless of the highly contested debates surrounding “indigeneity” or “being indigenous,” especially in Indonesia (Hadiprayitno, 2017 ), we argue that Indigenous cultural communities and Indigenous peoples have similarities (i.e., they are often farming or agrarian societies) but also recognize their differences and diversity in terms of their farming practices, beliefs, traditions, and rituals. These socio-cultural factors and human and non-human interactions influence rice production; thus, these differences and diversity bring front-and-center the importance of needs-based, community-driven, and context-sensitive interventions or projects for rice farming communities. These are research areas best explored by sociologists, anthropologists, and cultural scholars.

Today, agriculture’s sociological, anthropological, and cultural research have gone beyond the classic technology adoption arena. In Indonesia, studies have explored farmers’ technical efficiency in rice production (e.g., Muhardi and Effendy, 2021 ), the similarities and differences of labor regimes among them (e.g., White and Wijaya, 2021 ), the role of social capital (e.g., Salman et al., 2021 ), and the reciprocal human–environmental interactions in the rice ecological system (e.g., Sanjatmiko, 2021 ). Disyacitta Nariswari and Lauder ( 2021 ) conducted a dialectological study to examine the various Sundanese, Javanese, and Betawi Malay words used in rice production. Rochman et al. ( 2021 ) looked into the ngahuma (planting rice in the fields) as one of the inviolable customary laws of the Baduy Indigenous cultural community in Banten, Indonesia.

In the Philippines, Balogbog and Gomez ( 2020 ) identified upland rice farmers’ productivity and technical efficiency in Sarangani. Aguilar et al. ( 2021 ) examined the drivers of change, resilience, and potential trajectories of traditional rice-based agroecosystems in Kiangan, Ifugao. Pasiona et al. ( 2021 ) found that using the “modified listening group method” enables farmers’ peer-to-peer learning of technical concepts. Sociologist Shunnan Chiang ( 2020 ) examined the driving forces behind the transformation of the status of brown rice in the country.

Social scientists could further look into the social, cultural, technological, and human–ecological interactions in the temporal and spatial studies of different rice farming regions in Indonesia and the Philippines. Other topics could include the cultural practices and the techno-social relationships of rice farmers (e.g., Shepherd and McWilliam, 2011 ) and other players in the rice value chain, local and indigenous knowledge and practices on agrobiodiversity conservation, historical and invasive pests and diseases, agricultural health and safety, farmer education, and aging agricultural infrastructures. Lastly, future researchers can explore the impacts of adopting rice farming technologies in the different stages or processes of the rice value chain. They can look into its short- and longer-term effects on farmers’ livelihoods and conduct comparative analyses on how it improves, or not, their livelihoods, and whether farmers regard them better compared to the traditional and indigenous practices and beliefs that their communities apply and observe in rice farming.

Social and environmental psychology

Our review yielded no article published on the social and environmental psychology aspects of rice farming in Indonesia and the Philippines, suggesting a new research frontier. The increasing demand for and competition over agricultural and natural resources due to climate change and population expansion (Foley et al., 2011 ) opens up new and emerging sociopsychological dilemmas for society to understand, answer, and, hopefully, solve. Social and environmental psychologists can help shed light on these questions, such as those related to understanding farmers’ pro-environmental agricultural practices (Price and Leviston, 2014 ), sustainable sharing and management of agricultural and natural resources (Anderies et al., 2013 ; Biel and Gärling, 1995 ), and understanding the psychosocial consequences of resource scarcity (Griskevicius et al., 2013 ). Broadly, social psychology examines human feelings, thoughts, and behaviors and how they are influenced by the actual, imagined, and implied presence, such as the effects of internalized social norms (Allport, 1985 ). Social psychologists look at the many facets of personality and social interactions and explore the impacts of interpersonal and group relationships on human behavior (American Psychological Association, 2014b ). On the other hand, environmental psychology examines psychological processes in human encounters with their natural and built environments (Stern, 2000 ). Environmental psychologists are interested in studying and understanding people’s responses to natural and technological hazards, conservation, and perceptions of the environment (American Psychological Association, 2014a ).

Using the Asian Journal of Social Psychology and the Journal of Environmental Psychology as benchmarks, we recommend that scholars explore the following uncharted or least studied areas of rice research in Indonesia and the Philippines: sociopsychological processes such as attitude and behavior, social cognition, self and identity, individual differences, emotions, human–environmental health and well-being, social influence, communication, interpersonal behavior, intergroup relations, group processes, and cultural processes. Researchers could also investigate the psycho-behavioral areas of nature–people interactions, theories of place, place attachment, and place identity, especially in rice farming. Other topics may include farmers’ perceptions, behaviors, and management of environmental risks and hazards; theories of pro-environmental behaviors; psychology of sustainable agriculture; and the psychological aspects of resource/land management and land-use change.

Climate change, weather extremes, and disaster risk reduction

Indonesia’s and Philippines’ equatorial and archipelagic location in the Pacific Ring of Fire (Bankoff, 2016 ; Parwanto and Oyama, 2014 ), coupled with their political, social, and economic complexities (Bankoff, 2003 , 2007 ; UNDRR and CRED, 2020 ), expose and render these countries highly vulnerable to hazards, such as typhoons, strong winds, tsunamis, storm surges, floods, droughts, and earthquakes. The accelerating global climate change increases the frequency and intensity of some of these hazards, such as prolonged droughts, torrential rainfalls causing floods, and super typhoons (IPCC, 2014 ). For example, torrential flooding, induced by heavy rains caused by low pressures and southwest monsoons, has been damaging lives and livelihoods, including rice production (Statista, 2021 ). The 2020 droughts caused over 12 trillion pesos (~US$239.40 billion) of economic losses in the Philippines (Statista, 2021 ) and affected millions of Indonesians (UNDRR, 2020 ). Prolonged drought in Indonesia has also exacerbated fire hazards, which caused transboundary haze pollution in neighboring countries, like Singapore and the Philippines, inflecting environmental health damages (Aiken, 2004 ; Sheldon and Sankaran, 2017 ; Tan-Soo and Pattanayak, 2019 ). Increasing sea-level rise due to anthropogenic climate change puts cities like Jakarta and Manila at risk of sinking in the next 30–50 years (Kulp and Strauss, 2019 ). The high vulnerability, frequent exposure, and low capacities of marginalized and poor Indonesians and Filipinos turn these hazards into disasters (Gaillard, 2010 ; Kelman, 2020 ; Kelman et al., 2015 ), negatively affecting rice agriculture.

Given these contexts, climate change, weather extremes, and disaster risks, vis-à-vis its impacts on the rice sector, are issues of profound interest to scholars and the Indonesian and Philippine governments. In the Philippines, climate adaptation studies include re-engineering rice drying systems for climate change (Orge et al., 2020 ) and evaluating climate-smart farming practices and the effectiveness of Climate-Resiliency Field Schools in Mindanao (Chandra et al., 2017 ). In Indonesia, where some rice farming communities are vulnerable to sea-level rise, scholars are experimenting to identify rice cultivars with high yields under different salinity levels (Sembiring et al., 2020 ). Hohl et al. ( 2021 ) used a regional climate model to develop index-based drought insurance products to help the Central Java government make drought-related insurance payments to rice farmers. Aprizal et al. ( 2021 ) utilized land-use conditions and rain variability data to develop a flood inundation area model for the Way Sekampung sub-watershed in Lampung, Sumatra. Others also looked at the science behind liquefaction hazards caused by irrigation systems for wet rice cultivation in mountainous farming communities like the 2018 earthquake-triggered landslides in Palu Valley, Sulawesi (Bradley et al., 2019 ).

Examples of climate mitigation-related studies in the Philippines include investigating the social innovation strategies in engaging rice farmers in bioenergy development (Minas et al., 2020 ) and evaluating the environmental performance and energy efficiency of rice straw-generated electricity sources (Reaño et al., 2021 ). Doliente and Samsatli ( 2021 ) argue that it is possible to combine energy and food production to increase farm productivity and reduce GHG emissions with minimal land expansion. Other studies have looked into the potential of alternate wetting and drying irrigation practices to mitigate emissions from rice fields (Sander et al., 2020 ).

Future work could explore the following topic areas: demand-driven research and capacity building on climate information and environmental monitoring; nature-based solutions for climate mitigation and adaptation; water–energy–food nexus in rice farming; the nexus of climate change and conflict in rice farming communities; the potentials and pitfalls of social capital in farmer’s everyday adaptation; just energy transitions in rice farming; vulnerabilities from and traditional/local/indigenous ways of adapting to climate change, including the various learning strategies communities use for its preservation; and examples, potentials, and barriers in adopting climate-smart agriculture technologies and practices.

Demographic transitions and aging farmers

Farmers are in various stages and speeds of aging globally (Rigg et al., 2020 ). Evidence of aging farmers in the Global North has been reported in Australia (O’Callaghan and Warburton, 2017 ; Rogers et al., 2013 ), the Czech Republic (Zagata et al., 2015 ), England (Hamilton et al., 2015 ), Japan (Poungchompu et al., 2012 ; Usman et al., 2021 ), and the United States of America (Mitchell et al., 2008 ; Reed, 2008 ; Yudelman and Kealy, 2000 ). Similarly, in the Global South, HelpAge International ( 2014 , p. 21) reported that “there has been a universal trend of an increase in the proportion of older people… attached to agricultural holdings… across [Low and Middle-income Countries in] Asia, sub-Saharan Africa, Latin America, and the Caribbean.” Moreover, farming populations are aging rapidly in East and Southeast Asia (Rigg et al., 2020 ) and southern Africa (HelpAge, 2014 ). Despite this, the literature on aging farmers in Southeast Asian countries remains scant, except for case studies conducted in some villages and provinces in Thailand (Poungchompu et al., 2012 ; Rigg et al., 2018 , 2020 ) and the Philippines (Moya et al., 2015 ; Palis, 2020 ).

Rice farmers’ quiet but critical demographic transformation in Indonesia and the Philippines has not received much attention from scientists, policymakers, and development practitioners. The impacts of aging farmers on the micro-, meso-, and macro-level agricultural processes and outcomes are important issues that require urgent attention. Studies done in other countries could guide future work to explore these questions in Indonesia and the Philippines. These include aging’s potential negative implications in terms of agricultural efficiency and productivity (e.g., Tram and McPherson ( 2016 ) in Vietnam, and Szabo et al. ( 2021 ) in Thailand), food security (e.g., Bhandari and Mishra ( 2018 ) in Asia), farming continuity and sustainability (e.g., O’Callaghan and Warburton ( 2017 ) in Australia, Palis ( 2020 ) in the Philippines, and Rigg et al. ( 2018 , 2020 ) in Thailand), aging and feminization of farm labor (e.g., Liu et al. ( 2019 ) in China), cleaner production behaviors (e.g., Liu et al. ( 2021 ) in Northern China), youth barriers to farm entry (e.g., Zagata and Sutherland ( 2015 ) in Europe), and health and well-being of aging farmers (Jacka, 2018 ; Rogers et al., 2013 ; Ye et al., 2017 ).

Other critical new topics include the (dis)engagement and re-engagement of young people in rice farming; gender dynamics—including structures and systems of inclusion and/or exclusion—in rice production; the impacts of migration and return migration to farming households; community-based and policy-oriented case studies that provide examples of successfully engaging and retaining youth workers in farming; and social protection measures for aging farmers, to name a few.

Contemporary and emerging challenges

One of the biggest and most visible contemporary global challenges is the Covid-19 pandemic. Most pronounced is the pandemic’s impacts on the healthcare system and the economic toll it caused on the lives and livelihoods of people, including rice farmers. Only 0.18% (4 articles) of our dataset have investigated the impacts of Covid-19 on rice systems in Indonesia and the Philippines. Ling et al. ( 2021 ) assessed the effects of the pandemic on the domestic rice supply vis-à-vis food security among ASEAN member-states. They found that Singapore and Malaysia were highly vulnerable to a pandemic-induced rice crisis, while Brunei, Indonesia, and the Philippines are moderately vulnerable. They argued that Southeast Asian rice importers should consider alternative import strategies to reduce their high-risk reliance on rice supply from Thailand and Vietnam and look for other suppliers in other continents.

Rice prices did not change in the early months of the pandemic in Indonesia (Nasir et al., 2021 ); however, as the health emergency progressed, distributors and wholesalers incurred additional costs due to pandemic-induced mobility restrictions (Erlina and Elbaar, 2021 ). In the Philippines, San Juan ( 2021 ) argues that the global rice supply disruption due to the pandemic proves that the country cannot heavily rely on rice imports; instead, it should work on strengthening its domestic rice supply. To realize this, he recommended drastic investments in agriculture and research, rural solar electrification, and the promotion of research on increasing rice yields, boosting productivity, and planting sustainably as feasible steps on the road to rice self-sufficiency.

The ways and extent to which the pandemic negatively affected or exacerbated the vulnerabilities of rice farmers and other value chain actors remain an understudied area in the social studies of rice. Scholars could study the pandemic’s impacts in conjunction with other contemporary and emerging challenges like climate change, weather extremes, aging, conflict, and poverty. Scholars could also explore the medium- and longer-term impacts of the pandemic on rice production, unemployment risks, rice supply and nutrition security of farming households, and the potential and extent to which economic stimulus can benefit rice farmers, to name a few. Most importantly, the pandemic allows researchers and governments to assess the business-as-usual approach that resulted in the disastrous impacts of the pandemic on different sectors, including rice farmers, and hopefully devise strategies to learn from these experiences.

From our review of 2243 articles, cumulatively written by 6893 authors using almost 80,000 references, we conclude that a voluminous amount of rice research has been conducted in Indonesia and the Philippines since 2001. As in other reviews, (e.g., on energy research by Sovacool, 2014 ), our results show that women scholars remain underrepresented in rice research in Indonesia and the Philippines. While interdisciplinary collaboration is abundant, most of these studies belong to the natural sciences with minimal contributions from the social sciences, arts, and humanities. University and research institutions contributed the most to rice research in Indonesia and the Philippines: from hybrid rice cultivars, water management, and technology adoption to socio-cultural, political, economic, and policy issues. Influential scholars in the field were affiliated with the IRRI, which can be expected given the institute’s focus on rice, and key agriculture-focused universities and government bureaus such as the University of the Philippines and the PhilRice in the Philippines, and the Institut Pertanian Bogor University and the Universitas Gadja Maja in Indonesia. We also discussed some examples of economic, political, and policy studies; social, anthropological, and cultural research; social and environmental psychology; climate change, weather extremes, and disaster risk reduction; demographic transitions; and contemporary and emerging issues and studies on rice in the two Southeast Asian countries. Ultimately, we hope that this systematic review can help illuminate key topic areas of rice research in Indonesia and the Philippines and magnify the crucial contributions from and possible research areas and questions that interdisciplinary and comparative social scientists can further explore.

Data availability

The dataset analyzed in this study is available in the Figshare online repository via https://doi.org/10.6084/m9.figshare.17284814.v2 . All codes about Bibliometrix are available at https://bibliometrix.org/ .

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Acknowledgements

The work described in this paper was substantially supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. HKUST 26600521). Partial funding was also made available by the HKUST Institute for Emerging Market Studies with support from EY.

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Cuaton, G.P., Delina, L.L. Two decades of rice research in Indonesia and the Philippines: A systematic review and research agenda for the social sciences. Humanit Soc Sci Commun 9 , 372 (2022). https://doi.org/10.1057/s41599-022-01394-z

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Research Shows That Black Rice Can Be Very Beneficial for Your Eye Health

[table-of-contents] stripped

For years, you’ve probably heard that brown rice is a healthier choice than white rice . But could black rice be an even better option to fill your bowl? Perhaps.

Also known as “forbidden rice,” this type of rice isn’t actually black or forbidden. “In ancient China, it was known as forbidden rice because it was reserved for royalty, and ‘common’ people were not allowed to consume it,” explains Philadelphia nutritionist Stacey Woodson , RD, who is also an author of nutrition books for children. “But today, it is more widely available and enjoyed by people around the world.”

Though this whole grain looks black in the bag, it turns a dark shade of purple once it’s cooked (which gives it the other, more accurate nickname of “purple rice”). “Black rice has been part of the Asian diet for thousands of years,” says Natalie B. Allen , RD, a clinical associate professor of nutrition and dietetics at Missouri State University. “The deep color comes from anthocyanins, which are pigments found in purple and blue foods, and are typically lacking in the average American diet.” Like brown rice, black rice is unrefined, which means it contains all parts of the grain, including the fiber-filled bran and germ, giving it a nutritional edge over white rice, which has been stripped of those healthy parts.

Nutrition facts

Serving Size: 100-gram (from the brand Nature's Earthly Choice)

• 372 calories
• 3.49g total fat
• 0g saturated fat
• 79.1g total carbohydrates
• 4.7g dietary fiber
• 2.33g sugar
• 11.6g protein
• 0mg calcium (0% DV)
• 1.67mg iron (9% DV)
• 0mg vitamin C (0% DV)
• 0IU vitamin A (0% DV)

Health benefits

• It's high in antioxidants: We often think of fruits and vegetables when it comes to foods high in antioxidants — which are important for fighting off cell-damaging free radicals in the body —but whole grains often have a higher amount and more diverse array of antioxidants as well as the disease-fighting plant compounds called phytochemicals. The anthocyanins in black rice don’t just give the grain its pop of color: “Because of the presence of anthocyanins, black rice has a higher antioxidant content than other rice grains,” says New York nutritionist Melissa Rifkin , RD, who points out that this boost of antioxidants in your diet may help reduce the risk of heart disease , cancer, stroke and type 2 diabetes.
• It's a good source of fiber: Fiber is crucial to maintain a health digestive system —it can also reduce risk of cardiovascular diseases and type 2 diabetes. And some brands of black rice contain 4.7 g of dietary fiber per 100g . “Black rice is rich in nutrients and is higher in fiber, protein and iron than both white rice and brown rice,” says Chicago nutritionist Sara Chatfield , RDN. All that fiber as another benefit: It can help you feel full. “The higher protein and fiber content of black rice can help increase satiety at meals and may help with weight management,” Chatfield says.
• It boosts eye health: While certain red, yellow and orange foods such as carrots are well-known for containing carotenoids (pigments that can give your eye health a boost), black rice surprisingly contains them, too — specifically, lutein and zeaxanthin, says Allen. Numerous studies have shown that these two carotenoids can help protect the macula from damage by blue light, and improve visual acuity, and have been linked with reduced risk of age-related macular degeneration and cataracts.
• It has a lower glycemic index than white rice: One of the downsides of white rice is its high glycemic index (GI), which can cause a spike in blood sugar. If you’re concerned about your blood sugar levels because of type 2 diabetes or another reason, black rice is a tasty option that has a lower GI. And the vibrant addition of black rice to a meal isn’t just an aesthetic win: a diet that has different colors of fruits and vegetables is the best way to get the vitamins, minerals, and nutrients you need, according to the American Heart Association.

What does black rice taste like?

“I personally love black rice,” Chatfield says, calling it "a little chewier than other varieties of rice [with] a pleasant, nutty flavor.” She recommends pairing black rice with curries and stir-fries. “It will take a little longer to cook black rice than white rice, similar to brown rice,” Chatfield notes.

Allen prefers to prepare hers in a pressure cooker : “It's hands-off, but you can also steam or boil it,” says Allen. She adds, “It has a nutty flavor and goes well in a variety of dishes.”

Woodson recommends soaking the rice before cooking it: “Like many whole grains, black rice contains phytic acid, an antinutrient that can bind to minerals and reduce their absorption,” she says. “Soaking or fermenting the rice before cooking can help mitigate this effect.”

Is black rice healthier than white rice?

When choosing between black and white, it's helpful to remember how white rice is produced. Rice is naturally made up of three edible parts: the bran (the outer part that gives rice its color), the germ (an inner "embryo" that can grow into a new plant) and the endosperm (the substantial white part, within the bran). During the milling process, rice is "refined" by removing the bran and the germ. This process removes about 1/4 of the protein in a grain, and 1/2 to 2/3 or more of many of the nutrients, according the Whole Grains Council. However, enriched white rice will still provide some of the benefits that are lost during the refining process. So yes, black rice does have more nutritional value, but white rice may be more soothing for an upset stomach or as a dose of comfort food.

Can I eat black rice every day?

As with most delicious things in life, it’s all about moderation. “Black rice is high in fiber, which is a good thing overall, but don’t overdo it, since eating too much fiber too quickly could cause an upset stomach or gas,” warns Allen. “While black rice is highly nutritious, rather than eating it daily, it’s best to rotate it with other whole grain options for more dietary variety and to reduce your intake of arsenic [which is found in most types of rice],” says Chatfield.

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New study finds that Black and Latinx youth online engagement can foster a positive sense of self

Building on data from a project led by USC Rossier professor Brendesha Tynes, Naila Smith is the lead author of a new research paper that examines how online spaces created by Black and Latinx youth benefit their ethnic-racial identity development.

With social media use among many youth nearly constant, we often read reports of the adversities that young people encounter online, from impacts on their mental health to the dangers that meeting malicious strangers in real life can pose. While the negative effects of social media usage for teens should not be discounted, there are some benefits for Black and Latinx youth in particular as they navigate their ethnic-racial identity (ERI) online. Brendesha M. Tynes, Dean's Professor of Educational Equity at the USC Rossier School of Education, is a co-author of a newly published article led by Naila A. Smith, assistant professor of education at the University of Virginia, and supported by Daisy E. Camacho-Thompson, that shows how the race/ethnic- and civic-related online experiences of Black and Latinx adolescents are connected to their ERI development.

Black and Latinx youth tend to spend more time engaged online than their White peers, and they also spend more time than youth of other ethnic-racial groups making sense of what their ERI means to them and engaging civically and politically online. Exploring and seeking out information about one’s race/ethnicity, refining how one understands one’s race/ethnicity, and feeling positively or negatively about one’s race/ethnicity are factors in ERI development. 

Research on Black and Latinx adolescents’ online experiences has shown that they do face additional risks such as online racial discrimination and hate and viewing traumatic racial content. Online social connection can help Black and Latinx youth cultivate a sense of belonging to a social group that may help them make meaning of their identity as they encounter some of the harms in online spaces. This newly published article builds on some of Tynes’ previous work about how content youth are exposed to online impacts their ERI exploration.

Using data from the Teen Life Online and in Schools Project (TLOS), which Tynes directs, Smith and her team found that youth who can establish relationships online with friends of the same race/ethnicity experience more adaptive outcomes over time, meaning that in fostering online relationships with same-age, same ethnic/racial group peers these young people can better cope with some of the harmful information that they encounter online. 

Tynes’s TLOS data was one of the first datasets to investigate teens' online experiences across multiple years (three years) using both survey and interview data and a multi-racial sample of adolescents. While Tynes created the dataset, her collaborators and mentees led studies that were not previously included in the original proposal. 

Smith’s research interests include the development of racial and ethnically minoritized youth over time. She was curious about youths’ experiences in the online space over time and sought to examine the role of socio-cultural resources and assets in the experiences of Black and Latinx youth.  

“I was really interested in examining what factors contributed to ethnic-racial identity development, which is a sociocultural asset for Black and Latinx youth. In examining aspects of youths’ race- and civic-related online experiences and looking at how young people curate or create online spaces that meet their needs, we were able to show that there are these different ways that Black and Latinx adolescents are engaging online in their exploration of their world and their ethnic-racial background,” said Smith.

The study also found that earlier online activity is connected with ERI development one year later, meaning that race and civic-related online activities are important for young people’s feelings and behaviors in terms of their future ERI. Having a clearer idea of what their ERI means to Black and Latinx youth is associated with having better outcomes academically and mental health benefits.

“A major goal of the TLOS Project was to see what cultural resources youth bring to online spaces that might buffer them from some of the negative outcomes we might see that have been published in journals and in news articles. I wanted to paint a more holistic view of young people’s experiences online,” said Tynes. “Most of what we have published has been on the negative side, but I’m excited to have this manuscript focus on the positive experiences that young people are having online.” 

Smith started her collaboration with Tynes because of her advocacy for students and her deep knowledge of youth development. The two met at an academic conference when Smith was a graduate student.

“I wanted to meet Brendesha specifically because she was the foremost scholar on the online experiences of Black and Latinx youth, and I wanted to develop my expertise in the role of the internet in youth development. Her tremendous productivity and creativity are built on deep knowledge of a wide range of fields that inform her innovation in thinking about how we can support Black and Brown youth in their development specifically in online spaces,” concluded Smith. 

Smith and her co-authors want teachers and parents to know that Black and Latinx youth can benefit positively from the time they spend online, and that access to online information and experiences can support meaningful identity exploration. According to Smith, parents and teachers can help guide youth in their online ERI exploration and engage them in conversations about what they are learning to help them process the information that they are consuming. In schools where Black and Latinx youth may be in the minority or where they may not have access to materials in the curriculum that allow them to learn about their cultures and identities, supporting online activities around ERI is even more critical.

“With new laws banning certain books or talking about Black people’s history in the classroom in some states, people have to make an effort to make sure that kids are getting what they need to explore who they are,” said Tynes. “The digital literacy that young people need to sift through stereotypes and misinformation about their racial-ethnic group becomes more important in these places where the students cannot rely on their teachers to provide accurate information.”

The team’s findings may be used to support the creation of interventions to help adolescents create and curate online spaces where they can meet peers in their age range and ethnic/racial groups to help them with their relationship-building skills.

“Instead of the internet being a place where people are in constant danger, youth can craft spaces where their experiences are actually beneficial for their development, and these young people are doing that on their own,” said Tynes . “Parents and educators can support that exploration and provide guidance.”

Tynes is supporting that guidance by building a digital literacy and mental health intervention with a $4.6 million Transformational Research Award NIH grant. With the funds, Tynes seeks to research and provide adolescents with tools to cope with the negative messages they receive online and the skills to use digital media as a tool to excel in school. Tynes’s goal is to help youth thrive in their everyday lives as they navigate digital spaces. The newly designed, first-of-its-kind platform will have several modules and virtual reality experiences to help adolescents practice how to respond to some of their experiences online. The alpha version of this intervention is scheduled to launch in September 2024.

Brendesha Tynes

• Professor of Education and Psychology
• Director of CELDTECH

Center for Empowered Learning and Development with Technology

Article Type

Article topics, related news & insights.

April 4, 2024

Annual conference challenges presenters to dismantle racial injustice and construct educational possibilities

The 2024 American Educational Research Association Conference to feature over five-dozen USC Rossier scholars.

Yasemin Copur-Gencturk named Katzman/Ernst Chair for Educational Entrepreneurship, Technology and Innovation

As chair, Copur-Gencturk will work to address the underlying causes of inequity in the K–12 education system and create an environment that produces stronger educational outcomes for all.

Featured Faculty

• Yasemin Copur-Gencturk

March 28, 2024

Center for Education, Identity and Social Justice hosts USC Hybrid High students for visit and releases report on study of the school

The final report finds students’ sense of belonging to their high school and college declines after graduation and provides recommendations to improve student support.

• Shafiqa Ahmadi
• Darnell Cole

MINI REVIEW article

This article is part of the research topic.

Bioconversion of Insect Resources for Sustainability

Metabolic performance and feed efficiency of black soldier fly larvae Provisionally Accepted

• 1 Department of Chemistry and Bioscience, Aalborg University, Denmark

The final, formatted version of the article will be published soon.

The black soldier fly (BSF), Hermetia illucens is used in entomoremediation processes, because its larvae can utilize a variety of organic residues with high efficiency. However, feed efficiencies are variable and characterized by uncertainties. Recently developed growth and metabolic performance models predict that BSF larvae have utilized 53-58% of the feed components they have assimilated, in terms of carbon equivalents, for growth throughout their lifetime when reared on chicken feed across different studies. This is termed their average net growth efficiency. The remainder carbon has been lost as CO2. However, mass balances made under similar conditions show that the weight gained by BSF larvae corresponds to only 14-48% of the feed substrates removed, the substrate conversion efficiency. Both performance indicators show even greater variability if more feed substrates are considered. Feed assimilation and growth rates, costs of growth, maintenance and larval lifespan have been shown to affect how efficiently BSF larvae convert feed into growth. The differences between average net growth efficiencies and substrate conversion efficiencies further indicate that feed is often not utilized optimally in entomoremediation processes, and that the overall yield of such processes is not determined by larval performance alone but is the result of processes and interactions between larvae, substrates, microbes, and their physical environment.The purpose of this paper is to illustrate how quantification of the metabolic performance of BSF larvae can help to improve our understanding of the role of the larvae in entomoremediation processes.

Keywords: Hermetia illucens, Growth models, Metabolic models, Substrate conversion efficiency, Net growth efficiency

Received: 06 Mar 2024; Accepted: 08 Apr 2024.

Copyright: © 2024 Eriksen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Niels T. Eriksen, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark

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