A perspective on the benefits of consumption of parboiled rice over brown rice for glycaemic control.

PURPOSE: Rice is a staple food for over 3.5 billion people worldwide. The nutritional content of rice varies with different post-harvest processing techniques. Major varieties include brown rice (BR), white rice (WR) and parboiled rice (PBR). While consumption of BR is advocated due to its higher nutritional content compared to other varieties, some studies have indicated lower post-prandial blood glucose (PPBG) levels when PBR is consumed. This apparent benefit of PBR consumption is not well publicised and no commentaries on underlying mechanisms are available in literature. METHODS: In this review, we looked into differential nutrient content of PBR, as compared to BR and WR, and tried to understand how their consumption could be associated with glycaemic control. Various roles played by these nutrients in mechanisms of insulin secretion, insulin resistance, nutrient absorption and T2DM-associated inflammation were reviewed from literature-based evidence. RESULTS: We report differential nutritional factors in PBR, with respect to BR (and WR), such as higher calcium and selenium content, lower phytic acids, and enriched vitamin B6 which might aid PBR's ability to provide better glycaemic control than BR. CONCLUSION: Our interpretation of reviewed literature leads us to suggest the possible benefits of PBR consumption in glycaemic control and its inclusion as the preferred rice variant in diets of T2DM patients and at-risk individuals.

Fractionation of Raw and Parboiled Rice Husks with Deep Eutectic Solvents and Characterization of the Extracted Lignins towards a Circular Economy Perspective.

In the present work, rice husks (RHs), which, worldwide, represent one of the most abundant agricultural wastes in terms of their quantity, have been treated and fractionated in order to allow for their complete valorization. RHs coming from the raw and parboiled rice production have been submitted at first to a hydrothermal pretreatment followed by a deep eutectic solvent fractionation, allowing for the separation of the different components by means of an environmentally friendly process. The lignins obtained from raw and parboiled RHs have been thoroughly characterized and showed similar physico-chemical characteristics, indicating that the parboiling process does not introduce obvious lignin alterations. In addition, a preliminary evaluation of the potentiality of such lignin fractions as precursors of cement water reducers has provided encouraging results. A fermentation-based optional preprocess has also been investigated. However, both raw and parboiled RHs demonstrated a poor performance as a microbiological growth substrate, even in submerged fermentation using cellulose-degrading fungi. The described methodology appears to be a promising strategy for the valorization of these important waste biomasses coming from the rice industry towards a circular economy perspective.

Bioremediation and biomass production from the cultivation of probiotic Saccharomyces boulardii in parboiled rice effluent.

The parboilization of rice generates 2 L of effluent per kilogram of processed grain. Several methodologies have previously been tested with the aim of reducing the environmental impact of this effluent. The objective of this study was to evaluate the bioremediation of parboiled rice effluent supplemented with sucrose or residual glycerol from the biodiesel during the cultivation of the Saccharomyces boulardii probiotic. In the first stage of the experiment, cultures were grown in orbital shaker, and five media compositions were evaluated: 1) parboiled rice effluent; 2) effluent supplemented with 1% sucrose; 3) effluent supplemented with 3% sucrose; 4) effluent supplemented with 15 g.L-1 of biodiesel glycerol and 5) standard yeast culture medium (YM). The addition of 1% of sucrose generated the most promising results in terms of cell viability, removal of nitrogen, phosphorus and chemical oxygen demand (COD). From these results, four independent cultures were grown in a bioreactor using effluent +1% of sucrose as the medium. This assays generated a mean of 3.8 g.L-1 of biomass, 1.8 × 1011 CFU.L-1, and removal of 74% of COD and 78% of phosphorus. Therefore, the cultivation of Saccharomyces boulardii in parboiled rice effluent supplemented with 1% sucrose may represent a viable method by which the environmental impact of this effluent can be reduced while simultaneously producing probiotic culture for use in animal production.

Influence of sodium chloride and vacuum impregnation on the quality and bioactive compounds of parboiled glutinous rice.

This study investigated the effect of NaCl (2 and 4% (w/v)) and vacuum impregnation (VI) (150, 200, 250, and 300 Pa) on the quality parameters (water uptake, elongation ratio, visual color, and texture), tocols, γ-oryzanol and phenolic compounds of parboiled rice. Parboiling with NaCl and VI resulted in increased lightness and higher concentrations of bioactive compounds than rice parboiled by the traditional method. The highest concentration of tocopherols, γ-oryzanol, and phenolic acids (syringic, and ferulic acids) were obtained from parboiled rice with NaCl concentration at 2% (w/v) and VI at 250 and 300 Pa. As the NaCl concentration and VI levels increased the hardness L*, b* and ΔE values also increased, but the a* value and water uptake decreased. Results suggested that NaCl-VI soaking was observed to be an effective method for parboiling which promoted the visual color and enhanced the concentration of bioactive compounds in the parboiled rice.

Temperature dependence on hydration kinetic model parameters during rehydration of parboiled rice.

A study was carried out to relate the hydration behaviour with processing conditions of low amylose content parboiled rice which was dried at various temperatures (40, 50 and 60 °C). The rehydration characteristics of the parboiled rice (dehusked only) was then studied at various soaking temperatures (30, 40 and 50 °C) and time ( upto 3 h at every 30 min interval) and equilibrium moisture content of rehydration (EMC) was determined. The data were tested on three hydration equations viz., Peleg's, Exponential and Weibull equations. The experimental data were used to determine the model parameters. The goodness of fit for the models were evaluated by coefficient of determination (R(2)) and sum of square error (SSE). The results were indicated that the Weibull model fits better than the exponential model and Peleg's equation. Also, water transfer to paddy, was described by applying the Fick's diffusion model and the moisture diffusivity (D) was calculated. The Diffusivity values varied between 1.06 and 4 × 10(-11) m(2)/s.

Effect of ingredients on sensory profile of idli.

Idli is a traditional fermented food and is consumed in India and Srilanka. The objective of the present study is to select the ingredients for optimum desirable product characteristics and to identify the optimum ratios of ingredients and fermentation time with respect to sensory attributes using Response Surface Methodology (RSM). The sensory attributes included were color, appearance, texture, taste and overall quality. Preliminary trials were conducted using five variants of rice and common black gram dhal before framing a model using Central Composite Rotatable Design (CCRD). From the study it was found that a desirable score of 0.7439 was obtained for sensory attributes of idli made with the ratio of 3: 1.475 for IR20 idli rice and ADT3 variety black gram (with husk removed after soaking) fermented for 10.2 h. Principal Component Analysis (PCA) helped to discriminate the samples and attributes within the data matrix, depending upon their inter relationships.

The Glycemic Index of Indica and Japonica Subspecies Parboiled Rice Grown in Italy and the Effect on Glycemic Index of Different Parboiling Processes.

Rice is generally considered a high-glycemic index (GI) food, but numerous studies show that parboiling reduces the GI. There are no studies on GI of Indica and Japonica subspecies parboiled rice grown in Italy. The aim of this study was (1) to evaluate GI in different varieties of parboiled rice (ribe, white and brown long B, basmati, black, red, roma, and arborio); (2) to evaluate GI of same variety of rice subjected to different rice parboiling processes (parboiled ribe and parboiled long B with two different methods: flora and conventional method); (3) to evaluate GI of two by-products of parboiled rice: white and brown rice cake. Participants were 10 healthy individuals (20-30 years old, body mass index 18.5-25 kg/m2). Proximate composition and GI were determined by using standard methods. All parboiled rice assessed is low-GI (brown long B 48.1 ± 6.4 by flora method, ribe 52.0 ± 1.8 GI by flora method, black rice 52.3 ± 7.6 by flora method, long B 52.4 ± 3.9 by flora method, long B 53.4 ± 5.1 by conventional method, ribe 54.4 ± 4.3 GI by conventional method, Roma 54.4 ± 7.9 GI by flora method, and arborio 54.4 ± 7.9 GI by flora method), except red rice that is of medium-GI (56.1 ± 7.0 GI), and both classic and brown cakes that are high-GI (respectively, 83.3 ± 8.9 GI and 102.2 ± 5.5 GI). Parboiled rice is low-GI and so is favorable for the dietary management of metabolic disorders and celiac disease. Clinicaltrials.gov (NCT05333081).

Is contract arrangement source of income gain among parboiled rice stakeholders in Benin? A doubly robust analysis.

Rice supply remains insufficient for the world's consumption despite the agro-ecological potential, including the sub-Saharan African countries. The organization of the rice sector in Benin aims to a better profitability and above all in the increase in rice income of producers and processors. With this in mind, the objective of this study is to assess the impact of the contractual system on the earnings of parboiled rice stakeholders in the hill departments of Benin. For this reason, a random sample of 650 rice farmers spread over 400 producers and 250 processors made it possible to estimate of the Endogenous Switching Regression (ESR). The results of the estimates revealed that adherence to the agricultural contract as a function of socio-demographic factors such as human capital; gender; membership of an agricultural cooperative; have access to agricultural extension innovations and economic-institutional factors such as free entry into the market; access to quality agricultural products and access to credit. These results also confirm the positive effects of the acceptance of contracts on the parboiled rice income of the two actors. Adherence to agricultural contracts remains an effective agricultural policy likely to increase rice income in developing countries and in particular in the department of Collines which has a very high potential for arable land. The effective exploitation of these lowlands is a real source of increasing the rice supply in the perspective of insurance and guaranteeing better levels of food and nutritional security in Benin.

Starch gelatinization in the surface layer of rice grains is crucial in reducing the stickiness of parboiled rice.

Parboiled rice has high nutritional value but unpleasant palatability. In this study, rice stickiness was significantly reduced by steaming during the parboiling process; however, continuing steaming past certain durations no longer affected rice stickiness. It was also found: (i) the degree of starch gelatinization (DSG) increases and starch crystallinity decreases with increasing steaming time; (ii) the molecular size and chain length distribution (CLD) of leached starch for both white and parboiled rice are significantly different from those of native starch; (iii) the relation between leached amylopectin amount and rice stickiness explains the reduced stickiness by parboiling; and (iv) starch gelatinization in the surface layer of rice grains during parboiling might be critically important in blocking starch leaching, consequently leading to a less sticky texture. This study supplies a way to manage glutinous rice stickiness by parboiling for the production of non-sticky rice foods.

The influence of processing parameters of parboiled rice on its physiochemical and texture properties.

The impact of different parboiled rice process conditions on physical (whiteness and yellowness), chemical (amylose and fat contents), and texture (hardness and toughness) properties was studied. The parboiled rice was produced from the Suphanburi 1 variety. The correlation between chemical and texture properties was also analyzed. To study the effect of the soaking process, the time (2, 3, and 6 hr) and temperature (65 and 75°C) of soaking were altered, while the steaming condition was fixed at 100°C for 20 min. To study the effect of the steaming process, the soaking condition was fixed at 65°C for 6 hr while steaming condition was altered, including time (10 and 20 min) and temperature (90 and 100°C). The results show that the different conditions influenced the physical and chemical properties of parboiled rice. The amylose content was negatively correlated (Hardness, r = -0.52) (Toughness, r = -0.38) and fat content was positive low correlated (Hardness, r = 0.20) (Toughness, r = 0.12) with textural properties. Due to the specification of parboiled rice for exportation varying according to customer requirements, the results of this research provided some useful information for parboiled rice factories.

Relationship of starch changes to puffing expansion of parboiled rice.

'Intan' variety of paddy (Oryza sativa) was tested for puffing. It was parboiled under a wide range of paddy moisture content, steaming pressure and time, as also temperature and time of sand heating. The resulting milled rices were studied for their diverse properties including puffing. Indices of starch changes in the samples were calculated as: (1) gelatinisation index from the solubility of amylose in 0.2 N KOH; (2) amylopectin retrogradation from the post-production drop in room-temperature hydration power of the parboiled paddy during air-drying, (3) thermal breakdown of starch from the drop in gel permeation chromatographic fraction I of starch; lipid-amylose complexation indirectly from (4) drop in rate of water uptake during cooking and (5) cooked-rice firmness. It was found that the puffing expansion was very highly correlated with the combined above 5 indices of starch changes, as much as 90% of the variation in puffing being explainable on that basis. Puffing was promoted by gelatinisation as well as lipid-amylose complexation, but was retarded by amylopectin retrogradation and probably starch breakdown.

Microwave Parboiling: Reduction in Process Time, Browning of Rice and Residual Phosphorus Content in the Waste Water.

The conventional prolonged parboiling process results in high operation cost and grain darkening, which may limit consumption. Moreover, residue generation by rice industries is another challenge. The objective of this study was to evaluate the use of microwave irradiation during soaking and gelatinization stages of parboiling rice. Processing time, colorimetric profile, broken and nongelatinized grains, sucrose and glucose content, free 5-hydroxymethyl-2-furfural, and residual phosphorus were evaluated. As the soaking and gelatinization times during microwave treatments increased, the colorimetric parameters increased; however, the values were lower than those with the conventional process. Regardless of soaking time, a decrease in broken and nongelatinized grains was obtained by using the lowest steaming time (5 min). Additionally, lower residual phosphorus content was found in soaking water (10 and 20 min) when using microwave irradiation. Under favorable conditions, a reduction in the levels of broken and nongelatinized grains, residual phosphorus, and color changes was observed, indicating that microwave irradiation may be more beneficial than conventional parboiling. PRACTICAL APPLICATION: Parboiling requires a high volume of water and soaking time, which leads to high costs, underutilization of infrastructures, and high residue in the water after processing. The rapid parboiling process involves the use of microwaves during the soaking and gelatinization stages. The main advantages of the microwave parboiling process include reduced processing time, ranging from 83% to 95%, higher gelatinization, greater yield, reduced darkening, and reduced residual phosphorus in the effluents by 60%. This report can aid industries in streamlining their processes, thereby providing a high-quality, lower cost, and environmentally safe product.

Iron-fortified parboiled rice - A novel solution to high iron density in rice-based diets.

The present study pioneered an investigation of a novel and cost-effective approach to fortify Fe in rice and to greatly improve Fe nutrition in rice-based diets through parboiling, though it remains at its preliminary phase. Rice grains of seven cultivars were parboiled in deionised water containing different levels of Fe chelate made by mixing different proportions of Fe sulfate (FeSO4) with ethylenediaminetetra-acetic acid disodium salt (Na2EDTA). Adding Fe to the parboiling water resulted in an increased Fe concentration in the most grain, effectively where FeSO4 and Na2EDTA were mixed at 2:1 molar ratio (11.16g Fe per 100g raw paddy grain). This treatment resulted in Fe concentrations in white rice milled for 60s and 120s, which were 20-50 times higher than those in the unfortified milled raw rice grains. The Fe concentrations in milled rice grains were 50-150mg Fe kg(-1) in 60s milled grains with a slight reduction in 120s milled grains. Perls Prussian blue staining of the cross section of Fe-fortified parboiled rice grains suggested inward movement of added Fe into the endosperm through the apoplastic pathway in the dorsal region of the rice grain. The retention rates of fortified Fe varied among the different cultivars, possibly due to different physical-chemical properties of the grains. The percentages of soluble fraction of the total Fe were higher than 50% in all cultivars tested, indicating its high bioavailability potential, though it remains to be evaluated. The present findings provided a preliminary basis for further investigation of this innovative technique, before its adoption by parboiled rice industry, such as optimising the levels of Fe addition and industrial process and Fe bioavailability in Fe-fortified-parboiled rice.

The Effect of Cold Treatment of Parboiled Rice with Lowered Glycaemic Potency on Consumer Liking and Acceptability.

A significant reduction in rice starch digestibility and subsequent postprandial blood glucose responses following extended cold treatment (at 4 °C for 24 h) have been demonstrated in both in vitro and in vivo studies, respectively. The impact of cold treatment was more significant for parboiled rice compared to other rice varieties. This study aimed to investigate consumer liking of sensory characteristics that may influence consumer acceptability of three available rice products in the Auckland region (medium grain white, medium grain brown and parboiled rice, which were either freshly boiled or cold-treated and reheated). The consumer liking of sensory characteristics (colour, taste, flavour, and texture) of each rice sample were accessed using visual analogue scales (VAS) in a randomized single blind setting. In the second stage, the participants evaluated their acceptability on VAS after the nutritional value and the characteristics of the rice samples were revealed. Sixty-four rice consumers reported higher likings of sensory characteristics of cold-treated parboiled rice and medium grain brown rice. The effect of cold treatment on the liking of sensory characteristics was more significant for parboiled rice (p < 0.05). Participants who are between 36 and 55 years old and consume rice domestically more than 10 times per month preferred cold-treated brown rice (73.8% of the participants' population (67.4%, 80.2%)) and parboiled rice (74.3% of the participants' population (67.9%, 80.7%)) (p < 0.001). As a result, cold-treated reheated parboiled rice received higher likings and acceptability and could be recommended and accepted as a healthier replacement of the daily staple meal.

Parboiled rice metabolism differs in healthy and diabetic individuals with similar improvement in glycemic response.

BACKGROUND: White rice is a popular staple food; however, its high glycemic effect makes it an unfavorable choice for people with type 2 diabetes. OBJECTIVES: We hypothesized that the consumption of parboiled rice (PBR) reduces postprandial blood glucose concentration and appetite similarly to brown rice (BR) in diabetic people compared to white rice (WR). The objectives were to explore the effect of PBR on the pattern of blood glucose concentration and satiety in type 2 diabetic patients compared with healthy individuals. METHODS: Subjects were randomly administered 50 g of available carbohydrate from PBR, WR, or BR. Blood glucose and appetite were measured at 0, 15, 30, 45, 60, 90, and 120 min after ingestion of the rice samples. RESULTS: The postprandial blood glucose responses were significant among the healthy and diabetic subjects after consumption of the three rice samples. On the subjective appetite assessment, the response to the amount of food subjects could consume was significantly lower for healthy subjects after ingestion of PBR only. Despite these differences in rice metabolism between the two study groups, the area under the curve for the blood glucose response was reduced by 35% and 38% after consumption of PBR in diabetic and healthy subjects, respectively. Blood glucose responses to WR and BR however, were not significantly different from each other in either group. CONCLUSIONS: We conclude that PBR is a better alternative to WR or BR for diabetic individuals to control postprandial hyperglycemia.

Effect of modified atmosphere packaging on the quality of germinated parboiled brown rice.

Germinated parboiled brown rice (GPBR) is a healthy Thai food. To extend the quality of GPBR cv. KDML 105 with 8.06% moisture content, the effects of three packaging conditions on the characteristics of GPBR were investigated. GPBR in laminated (nylon/LLDPE) bags was sealed as follows: vacuum-sealed, 40% N2-sealed with 60% CO2 (60% CO2+40% N2), or 100% N2-sealed before storage under ambient conditions (30±2°C, 70±5% RH) for 15 months. GPBR in all the packages exhibited delayed fungal proliferation and very low aflatoxin B1 contamination (<0.82 µg/kg). The 100% N2-sealed package was the best treatment to preserve GPBR quality, as indicated by the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity and free fatty acid content as well as the least rancidity and brownness. As observed through a scanning electron microscope, compared with vacuum-sealed packages and those sealed with 60% CO2+40% N2, the lowest hardness texture and the least elongation of cooked rice in 100% N2-sealed package were linked to a lesser compact GPBR endosperm ultrastructure.

Improvement of the quality of parboiled rice by using anti-browning agents during parboiling process.

Browning occurs in parboiled rice as a result of the Maillard reaction that negatively affects consumers' acceptability. The aim of this study was to evaluate the ability of gallic acid, glycine, reduced glutathione and l-cysteine at 0.1, 0.5, 1.0 and 2.0% levels to inhibit browning reactions during the parboiling of rice. Gallic acid and l-cysteine did not exhibit browning inhibition effect at the studied levels. On the other hand, glycine and the higher concentrations of reduced glutathione (1.0 and 2.0%) were able to promote a whiter color and a low free 5-hydroxymethyl-2-furaldehyde content (HMF). The highest level of 2.0% for glycine and reduced glutathione favored protein extractability and a weaker protein-starch matrix, roughly increasing the broken grains percentage. Cooking time changed just for reduced glutathione-treated rice, as a result of their weaker protein-starch matrix and the greater ability of the grains to soften during cooking.

Effect of Cold Storage and Reheating of Parboiled Rice on Postprandial Glycaemic Response, Satiety, Palatability and Chewed Particle Size Distribution.

Background: Globally, hot cooked refined rice is consumed in large quantities and is a major contributor to dietary glycaemic load. This study aimed to compare the glycaemic potency of hot- and cold-stored parboiled rice to widely available medium-grain white rice. Method: Twenty-eight healthy volunteers participated in a three-treatment experiment where postprandial blood glucose was measured over 120 min after consumption of 140 g of rice. The three rice samples were freshly cooked medium-grain white rice, freshly cooked parboiled rice, and parboiled rice stored overnight at 4 °C. All rice was served warm at 65 °C. Chewing time was recorded. Results: incremental area under the curve (iAUC) of the control rice, freshly cooked medium-grain white rice, was the highest: 1.7-fold higher (1.2, 2.6) than reheated parboiled rice (p < 0.001) and 1.5-fold higher (1.0, 2.2) than freshly cooked parboiled rice (p = 0.001). No significant difference in postprandial glycaemic response was observed between freshly cooked and reheated parboiled rice samples (p = 0.445). Chewing time for 10 g cold-stored parboiled rice was 6 s (25%) longer and was considered more palatable, visually appealing and better tasting than freshly cooked medium-grain (all p < 0.05). Conclusions: For regular consumers of rice, reheating cooked rice after cold storage would lower the dietary glycaemic load and, in the long term, may reduce the risk for type 2 and gestational diabetes. More trials are needed to identify the significance.

Effects of the traditional method and an alternative parboiling process on the fatty acids, vitamin E, γ-oryzanol and phenolic acids of glutinous rice.

The impacts of traditional and alternative parboiling processes on the concentrations of fatty acids, tocopherol, tocotrienol, γ-oryzanol and phenolic acids in glutinous rice were investigated. Differences between the two methods were the soaking temperatures and the steaming methods. Results showed that parboiling processes significantly increased the concentrations of saturated fatty acids (SFA), mono-unsaturated fatty acids (MUFA), γ-oryzanol, γ-tocotrienol and total phenolic acids (TPA) in glutinous rice, while α-tocopherol, γ-tocopherol and polyunsaturated fatty acids (PUFA) decreased (p<0.05). Both the traditional and alternative parboiling methods increased the levels of γ-oryzanol by three or fourfold compared with the level of γ-oryzanol in raw rice. Parboiling caused both adverse and favorable effects on phenolic acids content (p<0.05). We found that glutinous rice, parboiled using our newly developed method, had higher levels of PUFA, total vitamin E, γ-oryzanol, hydrobenzoic acid, hydroxycinnamic acid and TPA compared to the traditional method.

Current techniques in rice mill effluent treatment: Emerging opportunities for waste reuse and waste-to-energy conversion.

Rice mills release huge volumes of wastewater and other by-products when processing paddy rice. The wastewater often contains toxic inorganic and organic contaminants which cause environmental damage when released. Accordingly, cost-effective techniques for removing contaminants are needed. This article reviews current processes for curbing pollution and also reusing and recycling waste products. Novel techniques exist for converting waste products into energy and value-added products.