Physicochemical Properties Of Rice Research Articles

Antioxidant Activity, Glycemic Response, and Functional Properties of Rice Cooked with Red Palm Oil.

High rice consumption levels accompanied by a lifestyle lacking in physical activity leads to obesity and diabetes due to the rice consumed generally has high digestibility and high glycemic index. Red palm oil (RPO) is a vegetable oil suggested to have the potential to reduce starch digestibility and increase the bioactive compounds of rice. This research aimed to find out the best cooking method to produce rice with a sensory quality similar to regular rice and to study the effect of the best cooking method on the glycemic response and physicochemical properties of rice. The results showed that RPO addition increased the antioxidant activities and total carotenoid levels of rice. The addition of RPO after cooking has better antioxidant activity and total carotenoid than before cooking. Adding 2% RPO before or after cooking produced rice with similar or better sensory quality than regular rice. Rice cooked with 2% RPO added before cooking had a lower glycemic response than regular rice, which was suggested to be caused by the increasing formation of the amylose lipid complex and the triglycerides that protected the starch from amylase enzyme. The formation of the amylose lipid complex and triglyceride layers protecting rice starch was confirmed by the new peaks of the FTIR spectra, the appearance of oil-coated starch morphology, and the changes in the proportion of C and O atoms. In conclusion, the addition of 2% RPO before the cooking process can be considered as a cooking method to produce rice for diabetic patients.

A comparative study on physicochemical properties of rice and starch of white rice, black rice and black glutinous rice

Rice is a staple food for Indonesians and Asians in general. It is rich in starch, a component that can be developed as a texture agent, filler, or raw material for edible films, encapsulation, or other products. The characteristics of the starch produced will determine its functional properties. This study aimed to characterize the physicochemical properties of rice and starch of white rice, black rice, and black glutinous rice. In this study, rice was extracted using an alkaline method to obtain rice starch. The processing of rice into starch can change some of its characteristics. A comparative study was also conducted on rice starch. The results showed that the starch contents of white, black, and black glutinous rice were 85.48; 86.67; and 83.56% (db). Black glutinous rice contains more amylopectin than black and white rice. Resistant starch in the rice fractions was greater than the amount of resistant starch in the starch fractions. Black rice contained anthocyanins of 323.85 mg/100 g, while the anthocyanins in black glutinous rice reached 219.35 mg/100 g. Although in very small amounts, anthocyanins were detected in black rice and black glutinous rice starch fractions. The starch fraction has much lower antioxidant activity compared to that in the form of rice. It appears on all types of rice. The peak viscosities of the starch of white rice, black rice, and black glutinous rice were 3627, 5448, and 5001 cP with pasting temperatures of 79.10°C, 80.60°C, and 80.90°C. Physicochemical and pasting properties of the rice fraction and the starch fraction from white, black, and black glutinous rice provide complete information to be used as a basis for the manufacture of food products.

The differences in metabolites, starch structure, and physicochemical properties of rice were related to the decrease in taste quality under high nitrogen fertilizer application

Nitrogen fertilizer application is one of the key cultivation practices to improve rice yields. However, the application of high nitrogen fertilizers often leads to a reduction in the stickiness of the rice after cooking, thus reducing the taste quality of rice. Moreover, there are differences in taste quality among rice varieties, and the mechanism has not been studied in depth. In this study, two rice varieties (Meixiangzhan2hao and Exiang2hao) were planted under two nitrogen fertilizer levels. The physicochemical properties and taste quality of the rice were determined after maturity. Our results showed that high nitrogen fertilizer level alters tryptophan metabolism in rice, increasing most amino acid content and protein content in rice. The high content of protein and the higher short-range ordered structure of starch inhibited the gelatinization characteristics of starch and reduced the taste quality of rice. Under high nitrogen fertilizer application, Exiang2hao showed smaller increases in protein content, lower level of amylose and relative crystallinity, and higher content of lipid metabolites. These differences in chemical substances resulted in a less pronounced reduction in the taste quality of Exiang2hao. In this study, the taste quality of different rice varieties under different levels of nitrogen fertilizer application was analyzed, providing new ideas for future improvement of rice taste quality.

Effect of pulsed electric field on physicochemical properties of rice and black gram fermented batter

AbstractThis study aimed to investigate the effect of PEF treatment (5, 20, and 35 kV/cm) on functional, physicochemical, and microbiological properties of rice and black gram fermented batter. The PEF treatment efficaciously inhibited the total bacterial, yeast, and mold count from 1 × 107 to 1.8 × 105 CFU/gm and 3.7 × 103 to 4.1 × 102 CFU/gm, respectively at 35 kV/cm. PEF treatment significantly improved protein solubility, reducing sugar, total phenolic content, and antioxidant activity in the fermented batter. Herschel–Bulkley model best described the change in apparent viscosity which significantly decreased in PEF treated samples. Further, FTIR analysis of the PEF treated sample exhibited an increase in the area of percentage in each functional group. The results of the study suggest that the potential of PEF treatment at 20 kV/cm enhanced bioactivity and bioavailability of protein, and carbohydrate content as well as impeded the microorganisms to avoid over‐fermentation.Practical applicationsPEF technology effectively inhibits or inactivates the microorganisms in rice and black gram fermented batter and is highly suitable to avoid over‐fermentation without major changes in the physicochemical properties of batter. Therefore, this study promotes inevitable scientific information that could further investigate the industrial production of fermented rice and black gram batter with targeted physicochemical properties through PEF treatment. This also creates new opportunities for food industries to strategically diversify microbial arrest aspects in the commercial fermented batter.

The Variation of Rice Quality and Relevant Starch Structure during Long-Term Storage

The main substances of rice are starches, which vary their metabolism during storage. We conducted a series of tests including rice physicochemical properties, edible quality, starch content and chain length distribution along with starch structure variation to disclose the shift of rice quality by observing the changes of rice during storage. The results showed that: (1) the rice deterioration occurred as time passed, and the germination rate decreased from 70.8% to 29.4% during the storage; (2) fatty acid values increased significantly during long-term storage; (3) electrical conductivity increased as time passed; and (4) the two-year-storage rice showed significantly decreased viscosity and edible quality after sensory evaluation, decreased hardness and damaged surface area of starch granules as storage time passed. Additionally, the damaged surface area of starch granules increased with storage time. Fourier transform infrared spectroscopy (FTIR) showed that the short-range order and spiral degree of rice starch first decreased in the first year and then increased over the storage time. Furthermore, X-ray diffraction showed that the main starch of rice was A-type crystalline. Meanwhile, apparent amylose content increased from 31.00% to 33.85%, then decreased to 31.75%. The peak viscosity reduced from 2735.00 mPa·s to 2163.67 mPa·s and the disintegration value was brought down from 1377.67 mPa·s to 850.33 mPa·s. Based on the results, rice should not be stored for more than 2 years under suitable granary conditions to maintain it at a good quality.

Phenolics from sea buckthorn (Hippophae rhamnoides L.) modulate starch digestibility through physicochemical modifications brought about by starch – Phenolic molecular interactions

The phenolics from sea buckthorn (SP) exert various physiological functions. This study examined the interactions of SP on the digestive and physicochemical properties of rice (RS) and wheat starch (WS), as well as the stability of starch-phenolics during digestion. The predominant phenolics from SP were syringic acid (22.14%), gallic acid (15.23%), and catechin (11.45%). The addition of SP manipulated the rheology of starch pastes and affected the rearrangement and multi-scale structures of starch gels. Fourier transform infrared spectroscopy and X-ray diffraction revealed that SP interacted with starch mainly through non-covalent hydrogen bonds, leading to a loose starch gel structure. The content of rapidly digestible starch of RS and WS decreased by 5.66% and 7.75%; the predicted glycaemic index of RS (91.65) and WS (89.34) decreased to 81.81 and 80.84, respectively, when the addition level of SP reached 15%, due to the inhibition activity of SP against digestive enzymes, as well as the molecular reorganisation of starch. After the in vitro digestion, the bioaccessibility of SP in starch gels increased by a magnitude of 2.58-fold (RS) and 2.98-fold (WS). These results provide evidence of using SP as functional formulations in controlling gel-like foods structure behaviours and modulating the glycaemic response of starchy foods.

Evaluation of Cooking and Physico-Chemical Properties of Rice

Evaluation of Cooking and Physico-Chemical Properties of Rice

Influence of harvest moisture content and milling duration on microwave‐dried rice physicochemical properties

AbstractBackground and ObjectivesHarvest moisture content (HMC) and milling duration are important factors that influence milled rice quality. The goal of this study is to determine the effect of HMC and milling duration on the physicochemical properties of long grain and medium grain microwave‐dried rice. A long‐grain hybrid rice cultivar (XL753) and a medium‐grain rice cultivar (Titan) with initial HMCs of 16%, 18%, and 20% (wet basis) were sourced from rice farms in Arkansas, USA. The rice samples were dried with the 915 MHz industrial microwave at a specific energy of 525 kJ/[kg‐grain]. The control samples were dried with natural air in an equilibrium moisture content chamber set at 25°C and 56% relative humidity. Following drying, the samples were milled at milling durations of 30, 45, and 60 s, and physicochemical properties were determined.FindingsHMC had significant (p < .05) impacts on head rice yield, crude protein content, and final viscosity of microwave‐dried rice for both cultivars. There were strong positive correlations (Titan: 0.86, XL753: 0.88) between HMC and head rice yield and negative correlations (Titan: −0.85, XL753: −0.62) between HMC and final viscosity of microwave‐dried rice. Milling duration significantly influenced the surface lipid content and whiteness index of microwave‐dried rice for both cultivars. Furthermore, milling duration had significant impacts on the starch damage content and trough viscosity of microwave‐dried rice cultivar XL753 but no significant impact on cultivar Titan. Statistical models predicted HMC of 20% and milling duration of 45 and 42 s for processing microwave‐dried rice cultivars Titan and XL753 respectively, to obtain rice with superior characteristics.ConclusionsHMC and milling duration significantly influenced some physicochemical properties of microwave‐dried rice. We recommend that further studies should be conducted on the cooking, sensory, and storage properties of microwave‐dried rice, to provide information on end‐use and consumer acceptability.Significance and NoveltyThis study provides science‐based information that is vital for optimizing the harvesting and processing conditions of rice dried using the 915 MHz industrial microwave.

Comparative studies on physicochemical properties of rice with germinated dark purple giant embryo rice and normal embryo rice

AbstractBackground and objectivesAs a cultivar developed by breeding, pigmented rice Keunnunjami has a dark purple pericarp and a giant embryo and has been found to possess strong antioxidant properties. The present study investigated the effect of 72‐hr germination on the physicochemical properties of Keunnunjami, in comparison with that of its parental pigmented normal embryo cultivar, Heukjinju, and ordinary normal brown rice.FindingsGermination generally increased the amounts of reducing sugar, amino acids isoleucine, leucine, phenylalanine, valine, alanine, cysteine, glycine, proline, and tyrosine, and minerals such as calcium, magnesium, and phosphorus while it decreased the levels of histidine, lysine, methionine, threonine, arginine, aspartic acid, glutamic acid, serine, and potassium in the rice grains. The germinated Keunnujami exhibited higher amounts of essential and non‐essential amino acids and reducing sugar than the germinated Heukjinju and normal brown rice. The starch granules from all rice samples showed holes and pits on the surface after germination.ConclusionsThese changes in the chemical composition and morphological properties are possibly due to partial hydrolysis of starch and protein caused by enzymes that were activated during germination.Significance and noveltyResults of this study could serve as the baseline information for evaluating the quality and possible food industry applications of germinated Keunnunjami.

Physicochemical and volatile characteristics present in different grain layers of various rice cultivars

Five rice cultivars were applied for investigating effect of milling degree on rice physicochemical properties. The first layer had the lowest peak viscosity, followed by the second and third layers, indicating the effect of non-starchy components on starch gelatinization behaviors. Consistently, more content of non-starch components in the first layer led to an enhanced gelatinization temperature. Rheological study demonstrated the G’ and G” were successively increased as the layer moved inward, indicating a stronger gel network due to the increased amylose content and crystallinity in the corresponding layer. This is the first study to reveal the second layer has the highest digestibility, suggesting both non-starch components and starch structure control starch digestion. Furthermore, analysis of volatile compounds found alcohols and ketones concentrated in the first layer, whilst compounds including (E,E)-2,4-decadienal, 3-octanone and 3-nonen-2-one only existed in the second layer, serving as an indicator for managing the rice quality during milling.

Effect of protein denaturation and lipid removal on rice physicochemical properties

The physicochemical properties of rice are influenced by their chemical components and their interactions. It has been demonstrated that the interactions among rice chemical components are enhanced by protein denaturation (PD) via heat treatment and by lipid removal (LR) via solvent extraction. The objective of this study was to investigate the impacts of PD, LR, and their combined treatments on the gelatinization and pasting properties, swelling power, and water solubility of four brown rice flours. Rice protein was denatured under a vacuum at 100 °C, and rice lipid was removed via hexane for varying times. The combined treatments were done in two ways, PD followed by LR (PD-LR), and LR followed by PD (LR-PD). The results showed that PD increased gelatinization temperatures, while LR decreased gelatinization temperatures. Both PD and LR reduced pasting and swelling properties; however, PD resulted in a greater decrease than LR. Polar lipids are proposed to serve as bridges to link denatured proteins and starch granules in the combined treatments, resulting in greater decreases in the pasting and swelling properties than the individual treatments. The results obtained in this study demonstrate the importance of starch-lipid-protein interactions on the physicochemical properties of brown rice flour.

Investigation of Changes in Grain Quality and Physicochemical Properties of Rice According to the Temperature during the Ripening Stage and Preharvest Sprouting

Investigation of Changes in Grain Quality and Physicochemical Properties of Rice According to the Temperature during the Ripening Stage and Preharvest Sprouting

Black rice (Oryza sativa L.) processing: Evaluation of physicochemical properties, in vitro starch digestibility, and phenolic functions linked to type 2 diabetes

Black rice is recognized for managing diabetes in Chinese folk medicine. Therefore, the present study investigates the effect of thermal treatments and the succeeding cooking on black rice physicochemical properties, phenolic composition, total antioxidant activity (TAA), enzymes and glycation inhibition in addition to starch digestibility. Thermal decomposition of anthocyanin and cyanidin-3-glucoside was evident across all processing methods and reflected in increasing levels of protocatechuic acid, while proanthocyanidins (TPAC) were susceptible to cooking. Roasting of grains sustained total phenolics (TPC), flavonoids (TFC), TPAC, and antilipase activity. Additionally, the combined effect of frying and cooking diminished TFC, TPAC, and α-glucosidase inhibition. The thermally treated grains showed pronounced activity against α-amylase, α-glucosidase, and glycation, whereas their cooked counterparts reduced the estimated glycemic index (eGI), and enhanced resistant starch (RS). Processed grains chrominance, TAA, and apparent amylose content (AAC) showed a significant correlation with phenolics. These findings are demonstrating that black rice processing is favorable for the dietary management of metabolic disorders such as diabetes and hyperlipidemia.

Effect of ultrahigh pressure on structural and physicochemical properties of rice and corn starch in complexes with apple polyphenols.

Ultrahigh-pressure (UHP) treatment, a non-thermal processing technology, exerts a bactericidal effect and affects food texture. How UHP treatments influence starch-polyphenol complexes has not yet been reported. Here, we studied the effects of UHP treatment on the structure of common rice starch (CRS)-apple polyphenol (AP) and common corn starch (CCS)-AP mixtures. Overall, UHP treatment decreased the particle size of the CRS-AP and CCS-AP composites. Furthermore, the ΔH values of the CRS-AP and CCS-AP mixtures decreased, and the heating stability was improved after UHP treatment. X-ray diffraction indicated that the relative crystallinity of the mixtures was unaffected by UHP treatment. Fourier-transform infrared spectroscopy proved that no new absorption peaks were observed in the infrared spectra, and the order of starch-AP was decreased after UHP treatment. These results indicated that UHP treatment inhibited the retrogradation of the starch-AP mixture. Our analyses of the microstructures of CRS-AP and CCS-AP mixtures showed increased folding and more pronounced network structures under high-pressure. These results provide a theoretical basis for further exploring the properties of starch-AP mixtures following UHP treatment and provide insights regarding the use of UHP treatments for food production. © 2020 Society of Chemical Industry.

Effects of heat, drought and their combined effects on morphological structure and physicochemical properties of rice (Oryza sativa L.) starch

High temperature (HT) and drought stress (WS) severely affect rice quality by altering the starch structure in rice. The morphological and physicochemical properties of starches isolated from two rice varieties grown under three stress treatment (HT, WS and WS + HT) during the grain filling stage were investigated. The results showed that WS increased amylose content (AC%) and the proportion of large starch granules (LSG) and made the surface of the starch granule smooth and flat. As a result, a lower relative crystallinity, surface order, swelling power, setback viscosity and gelatinization enthalpy were caused. HT decreased AC% and milled rice rate, but increased chalky rice rate, the number of LSG and the large air space and pits on the surface of the starch granules. As a result, a higher relative crystallinity, surface order, swelling power, setback viscosity and gelatinization enthalpy were caused. Similar results were observed under the treatment of WS + HT, indicating that there is a mild antagonistic effect on rice starch when the HT and WS occur simultaneously.

Effect of parboiling methods on the physicochemical characteristics and glycemic index of rice varieties

The effect of open steaming (HS) and pressure (PP) parboiling on the physicochemical characteristics and glycemic index (GI) of five different Indian rice varieties with varying amylose contents was investigated. Results showed that the severity of processing had a significant effect on the physicochemical properties of rice. PP resulted in reduced whiteness (18.83 ± 0.66 to 26.03 ± 1.27%), increased transparency (1.64 ± 0.05 to 2.05 ± 0.08%), hardness (6.66 ± 0.63 to 7.82 ± 1.19 kg) and equilibrium moisture content (117.59 ± 11.37 to 183.69 ± 39.46%db). PP rice also showed higher cooking time (40.28 ± 0.35 to 59.31 ± 0.69 min), water absorption ratio (4.52 ± 0.06 to 5.23 ± 0.04), and sedimentation volume than HS and non-parboiled counterparts. An increase in parboiling temperature significantly affected the pasting profiles of rice flour. Among the treated samples, the degree of gelatinization was higher for PP rice (70.80 ± 6.83 – 85.24 ± 1.48%). Alkali spreading value explained the lower gelatinization temperature for parboiled rice as compared with the non-parboiled counterpart. Higher amylose content of rice was associated with lower GI values and parboiled rice had a significantly lesser GI. The findings of this study provide insights on rice parboiling methods, particularly for the diabetic population.

Comparison of physicochemical properties, grain quality, and ultrastructure of rice cultivars

Genetic background, environmental conditions, and agronomical practices could influence yield components, grain quality, and physicochemical properties of rice. The study aim was to investigate the variations in yield potential, quality traits, and morphological observation among Akitakomachi (japonica), IR-28 (indica), and NERICA-4 (hybrid) varieties under the same environmental and agronomical conditions. For this, the cultivars were compared in a randomized complete block design with three replications at the paddy field of Tsukuba International Center, JICA, Tsukuba, Japan in 2017. All cultivars were transplanted at a spacing of 15×30 cm using three seedlings per hill. The results exhibited that Akitakomachi had a higher number of panicles per m2 (344.3), and the ripening ratio (94.3%) across all cultivars. In addition, IR-28 and Akitakomachi achieved significantly higher rough rice yield (6.9 t/h & 6.1 t/h), respectively, compared to NERICA-4 (4.9 t/h). However, NERICA-4 was associated with the significantly higher amylose and protein contents, which resulted in the reduction of the taste point than other cultivars. Furthermore, the lowest grain transparent (34.2%) and highest chalky grain (47.7%) were obtained in NERICA-4, which leads to lower grain quality. IR-28 and NERICA-4 were classified as long and slender grain types, whereas, Akitakomachi as a short and medium grain, respectively. The micrographs observation displayed that regular starch granules with polyhedral shape were arranged without air gaps in transparent grains of all cultivars. In contrast, the endosperm of chalky grains in NERICA-4 and IR-28 revealed that irregular starch granules with round shape were loosely packed. Thus, each cultivar should be considered based on growing regions and the cultivated aims.

Synergic effect of montmorillonite and microcrystalline cellulose on the physicochemical properties of rice husk/PVC composite

Rice husk, an agricultural waste material, was tried to make value added by preparing composite with microcrystalline cellulose and montmorillonite by melt blending process in different proportions. The interaction among the components was studied by Fourier transform infrared spectroscopy and X-ray diffractometry. The mechanical and thermal properties were studied through universal testing machine, dynamic mechanical analyzer and thermogravimetr ic analyzer. Scanning electron microscopy and transmission electron microscopy were used to analyze the surface morphology of the composites. Among the various composition the better synergistic effect was observed in composite PRMCC2 with 2 phr MCC and 3 phr MMT. Along with thermal and mechanical properties, PRMCC2 also showed better flame retardancy and water-resistant properties.

The effects of Enhanced UV-B Radiation on Root Morphology and Secretion Content of Rice (Oryza sativa Linn.)

A hydroponic experiment was carried out to study the effects of UV-B radiation (5.0kJ/m2) on root morphology and root exudates in the local rice variety Baijiaolaojing in a terraced field in the Yuanyang region of China. It was observed that UV-B radiation had the following impact on rice physicochemical properties (1) significant inhibition in both root biomass and the whole biomass of rice, (2) significant increase in the free amino acid and total phenol content secreted by roots on the 40th and 60th day of growth, (3) significant increase in the soluble sugar content in all three growth phases (4) significant increase in oxalic acid and succinic acid, (5) significant decrease in malic acid. The content of tartaric acid was not significantly impacted by the two treatments (natural light 0 kJ/m2, UV-B radiation (5.0kJ/m2). Therefore, UV-B enhancement significantly affects the content of low molecular organic acids in rice, which is closely related to its altered root morphology.

Efficacy of N-methyl-N-nitrosourea (MNU) Mutation on Enhancing the Yield and Quality of Rice

Mutation technology has been applied more in recent decades to achieve novel products that are not commonly found in nature. An experiment was conducted to examine the effects of an N-methyl-N-nitrosourea (MNU) mutation on the growth, yield, and physicochemical properties of rice. Seeds of two rice cultivars (K1: DT84, and K3: Q5), along with their mutant lines (K2: mutated DT84, and K4: mutated Q5), were sown, and the established seedlings were transplanted to an open field. Ten hills per plot were randomly selected to evaluate growth parameters, yield, and components. Physicochemical attributes, including protein, amylose, and lipid contents, as well as taste score were measured by a quality tester device. The results showed that plant length, tiller number, and panicle length were higher in mutant lines than those of their cultivars. Furthermore, mutant lines took longer to reach heading and maturity stage. The highest panicle number, spikelet number, repined ratio, 1000 grain weight, 1000 brown rice weight, and grain yield were obtained in mutant lines, as compared to cultivars. The greatest grain yield was obtained in the K4 mutant line (11.6 t/ha), while the lowest was recorded in the K1 cultivar (7.7 t/ha). Lower amylose, protein, and lipid contents were observed in mutant lines compared to those in cultivars. The taste score, which increased from 67.7 to 73.7, was found to be correlated with lower amylose, protein, and lipid contents. The mutation approach increased the grain length but decreased the grain width of tested varieties. This study highlights and suggests the importance of MNU mutation in terms of rice yield improvement with preferable quality.