Bran Layer Research Articles

The mechanism of bran layer removal in friction rice mills

The mechanism of bran layer removal in friction rice mills

BIOACTIVE SUBSTANCES AND THEIR POTENTIAL THERAPEUTIC PROPERTIES OF SORGHUM [SORGHUM BICOLOR (L) MOENCH

Sorghum is one of the important dryland C4 crops mainly grown in sub-saharan Africa and Asia and serves as a source of food, feed, fodder and biofuel. It is the main source of dry season ration to the livestock and provides nutrition and security for livelihood of poor farmers in rural areas. Sorghum can withstand drought and comes up well in adverse climatic conditions and hence, it is considered as an important climate resilient crop. Sorghum possesses diverse phytochemicals especially in the bran layer which represents a promising opportunity to be exploited as a functional food and to reduce the risk of non – communicable chronic diseases. Owing to high phenolic content and gluten free nature of sorghum and low glycemic index the grains are increasingly utilized for human consumption realising concept of eat right food for good health. Red sorghum bran is known as a rich source of anthocyanins. The bran and flour extracts analysis using various colorimetric methods including HPLC (High Pressure Liquid Chromatography) found with presence of several phenolic compounds like anthocyanins particularly 3-deoxyanthocyanin that includes apignenidin and luteolinidin, condensed tannin, ferulic acidetc., which provide the therapeutic properties of antioxidant, anti-cancer, anti-diabetic, prevention of cardiovascular diseases. The data collected from recent studies indicate that these molecules have a promising future as natural biofood agents for the treatment of various diseases, and this is particularly due to their strong antioxidant properties, in addition to modulating the intestinal microbiota. This review is made to understand the bioactive substances present in sorghum grains, their extraction and their potential therapeutic effects.

Germinated brown rice relieves hyperlipidemia by alleviating gut microbiota dysbiosis

Hyperlipidemia is a frequent metabolic disorder that is closely associated with diet. It is believed that brown rice, containing the outer bran layer and germ, is beneficial for the remission of hyperlipidemia. This study established a rat model of hyperlipidemia by feeding a high-fat diet. The hypolipidemic potential of germinated brown rice (Gbrown) and germinated black rice (a germinated black-pigmented brown rice, Gblack) were explored in the model rats, mainly in the aspects of blood lipids, lipases, apolipoproteins, and inflammation. The gut microbiota in hyperlipidemic rats receiving diverse dietary interventions was determined by 16S rDNA sequencing. The results showed that the intervention of Gbrown/Gblack alleviated the hyperlipidemia in rats, evidenced by decreased TC, TG, LDL-C, and apolipoprotein B, and increased HDL-C, HL, LPL, LCAT, and apolipoprotein A1. Gbrown/Gblack also weakened the inflammation in hyperlipidemia rats, evidenced by decreased TNF-α, IL-6, and ET-1. In addition, 16S rDNA sequencing revealed that the diet of Gbrown/Gblack elevated the abundance and diversity of gut microbiota in hyperlipidemia rats. At the phylum level, Gbrown/Gblack decreased Firmicutes, increased Bacteroidetes, and decreased the F/B ratio in hyperlipidemia rats. At the genus level, Gbrown/Gblack decreased Streptococcus and increased Ruminococcus and Allobaculum in hyperlipidemia rats. Some differential microbial genera relating to lipid metabolism were also determined, such as the Lachnospiraceae and Ruminococcus in the Gblack group, and the Phascolarctobacterium, Dorea, Turicibacter, and Escherichia-Shigella in the Gbrown group. Notably, the beneficial effect of Gblack was stronger than Gbrown. To sum up, the dietary interventions of Gbrown/Gblack contributed to the remission of hyperlipidemia by alleviating the dysbiosis of gut microbiota.

Ultrasound-assisted cellulase pretreatment and cooking with enzymatic hydrolysates enhance the freeze-thaw stability of brown rice

Brown rice (BR) is rich in nutrients and becoming a good source for convenience rice development. However, the bran layer of BR and freeze-thawing in food supply chains affects the rice texture and limits the palatability. This study aims to apply the preprocessing method of ultrasound-assisted cellulase (UAC) that has been demonstrated to improve the textural attributes of BR, and further make use of the enzymatic hydrolysates for rice cooking, to stabilize the texture against freeze-thawing. BR with cellulase pretreatment and addition of the enzymatic hydrolysates during cooking exhibited stable hardness and stickiness over five freeze-thaw cycles as compared to the rice cooked with water or the diluted hydrolysates. As observed by scanning electron microscopy and low-field nuclear magnetic resonance, BR cooked with the hydrolysates displayed more homogenous microstructure and the reduced water mobility against freeze-thawing, revealing that sugar and proteins in the hydrolysates contributed to promote the water holding capacity of cooked rice. Moreover, BR cooked with the hydrolysates exhibit noted advantages in fiber (0.23 g/kg) and proteins (0.19 g/kg) content. The combination of UAC pretreatment and cooking with the enzymatic hydrolysates provides a promising processing method for convenience brown rice with improved freeze-thaw stability and nutritional quality.

Effect of the degree of milling on the microstructure and composition of japonica rice

The effect of the degree of milling (DM) on the distribution of the residual bran layer on the surface of rice grains and subsequent rice quality is essential for rice milling technology. This study used scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to examine the microstructure of Japonica rice grains, the microstructural changes in different bran portions after milling, and the content and distribution changes of the elements and nutrients in rice after milling to identify the components that can quantify bran residue according to DM. The SEM results revealed that the thickness of the bran layer and the depth of the grooves in different parts of a rice grain varied, while the depth of the grooves differed between varieties. When DM was 12%, aleurone layer (Al) cells embedded in endosperm (En) remained in the dorsal area. It was speculated that this was the reason why there was no significant difference in bran degree when the DM estimated via grain weight loss increased from 10% to 14% ( P > 0.05). The EDS elemental mapping image showed the qualitative distribution of the elements, which was condensed in the bran and uniform in the En. The compositional changes revealed that milling caused the loss of rice nutrients, and the loss rate of DM at 0%–10% was more serious than that of DM at 10%–14%. Higher DM (>10%) could remove marginal bran from the dorsal groove. Therefore, the crude protein, ash, crude fat, dietary fiber, vitamin B1 (VB1), and vitamin B2 (VB2) content did not change significantly ( P > 0.05), while the magnesium (Mg), kalium (K), and phosphorus (P) levels decreased substantially ( P < 0.05). The microstructural and compositional changes indicated that the DM estimated via the grain weight loss increased from 2% to 10%, with the bran decreasing progressively. The DM estimated via the grain weight loss increased from 10% to 14%, with minimal changes in the residual bran in the dorsal grooves of the rice grains, while the Mg, P, and K levels presented precise DM indices during the rice milling process. This result will provide a theoretical reference for the accurate evaluations of DM.

The textural properties of cooked convenience rice upon repeated freeze–thaw treatments are largely affected by water mobility at grain level

Brown rice (BR) is a promising source for convenience rice that are mostly stored frozen. However, freezing and thawing may cause deterioration in rice texture quality. To investigate how rice texture is influenced by freeze–thaw cycles, BR, the pretreated BR with partially ruptured bran layer (UER) and white rice (WR) were cooked and treated with repeated freeze–thaw cycles, with their textural properties, variations in moisture distribution and starch structure being measured. Results showed that the repeated freeze–thaw treatment induced a progressive reduction in hardness and stickiness of all cooked rice. The reduced hardness of rice could be explained by the enlarged pore size of starch inside rice under scanning electron microscopy. Moisture migration in WR was the fastest responding to multiply freeze–thaw cycles, followed by UER, while water mobility in BR was slowest. Moreover, WR, BR and UER resulted in a similar extent of amylopectin retrogradation and chains length distribution after repeated freeze–thaw cycles. It indicated similar and minor effect of starch variations on determining the texture of different rice samples against freeze-thawing. Water mobility tended to be a main factor leading to the textural difference of fully gelatinized rice samples. This study focused on the relationship between water distribution and starch retrogradation, providing a better understanding on influences of multiple freeze-thawing on textural quality of cooked rice maintaining different extents of surface layer.

The diversity of phytic acid content and grain processing play decisive role on minerals bioavailability in rice

Rice is a staple food and important source of micronutrients for more than three billion people globally. However, the bioavailability of iron (Fe) and zinc (Zn) is affected by phytic acid (PA). In this work, we analyzed 67 genotypes for Fe, Zn and PA contents. Contrasting PA genotypes were selected in each category of high protein, scented, pigmented and general rice for bioavailability analysis. Our results explain that though Fe content in genotype PB 140 was high, the bioavailability was low which might be due to its higher PA content (21.03 g/kg). The Fe and PA are majorly located in outer bran layer of endosperm, therefore, its bioavailability was affected by PA. However, Zn bioavailability was not much affected by PA as it is distributed homogenously in the rice grain. Moreover, PA biosynthetic genes (IPK1, MIPS1) and grain specific phosphorus transporter gene (SPDT) expressed higher in the middle stage of grain filling which was correlated with higher PA accumulation. Our study provides an insight into the improvement of mechanism of Fe and Zn bioavailability in rice grain which help breeders involved in biofortification programme to develop high minerals bioavailable genotypes by targeting PA related genes.

Effects of hydrogen‐rich water on the nutritional properties, volatile profile and texture of germinated brown rice

SummaryIn the present study, we investigated the effects of hydrogen‐rich water (HRW) on the germination efficiency, chemical composition, biofunctional and volatile compounds, and texture of germinated brown rice (GBR). Our results showed that HRW (1.5 mg L−1) treatment significantly increased the germination efficiency of GBR by changing the migration of water during soaking. A chemical composition analysis showed that HRW treatment changed the contents of some biofunctional compounds and volatile components; increased the contents of soluble dietary fibre, thiamine, niacin, γ‐aminobutyric acid, some amino acids and K, P, Mn and Fe; and decreased the contents of starch and Na of GBR compared with those of GBR treated with regular pure water. Moreover, HRW treatment also improved the texture of GBR due to the changes in the ultrastructure of the bran layer and the decrease in insoluble dietary fibre. In summary, HRW is suggested to be applied in the processing of GBR since it can increase germination efficiency and improve the nutritional and eating qualities of GBR.

IN SILICO AND IN VIVO VALIDATION OF DIGESTION BEHAVIOR OF RICE IN THE ARTIFICIAL STOMACH ARK®

The effect of the physicochemical properties on the digestion behavior of rice was evaluated using the artificial stomach response kit (ARK®). Due to the presence of the external bran layer, brown rice (Rv3) showed delayed rates of gastric emptying, apart from a higher half emptying time (101.80 ± 1.20 min) than milled rice (Rv1 - 57.84 ± 7.49 min) and basmati rice (Rv2 - 77.93 ± 10.18 min). The bran layer of Rv3 inhibited the diffusion of the simulated gastric fluid and resulted in lesser particle breakdown and low glycemic index (GI). In comparison with the shaker digestion process, the mechanical force produced in the ARK® resulted in a higher degree of particle breakdown. An in silico approach successfully predicted the glucose response pattern of rice varieties with no statistical difference (at p&lt; 0.05) with the human in vivo datasets using the output obtained from ARK®. The GI obtained from ARK® was validated with in vivo data using Bland Altmann’s statistical tool which showed good agreement. The morphology, dimensions, capacity of the stomach chamber in the ARK® also resembled in vivo observations. The ARK® is proposed as an improved alternative for in vitro digestion studies.

Intact aleurone cells limit the hydrolysis of endogenous lipids in wheat bran during storage

This work aimed to elucidate the effect of aleurone cell integrity on the hydrolysis of endogenous lipids in wheat bran and flour. The distribution of lipases in the bran dissected layers (aleurone layer, outer pericarp and intermediate layer) and the lipid hydrolysis in the bran fractions and flour containing the aleurone cells with different integrity were investigated. The results indicated that 80% of the lipase activities in bran layers were associated with the aleurone layer. After centrifugal impact milling, the aleurone layer in commercial bran could be detached into the monolayer cell clusters with decreasing integrities as the particle size decreased. In the oil phase, intact aleurone cells did not limit the lipase activities in the bran fractions because the oil could penetrate into aleurone cells. During storage, the hydrolysis rates of endogenous lipids in the bran fractions and their mixed flour increased as the integrity of aleurone cells decreased; while after the aleurone cells were broken, the hydrolysis rates of endogenous lipids increased to be in line with the lipase activities in bran fractions, indicating the limitation of intact aleurone cells on lipid hydrolysis. These results gave a new understanding of the effect of aleurone cell structure on the interaction between lipases and lipids in wheat bran, and will facilitate the production of stable wheat bran and whole wheat flour.

Pre-gelatinization and cellulase addition improve fermentation performance and antioxidant activity of black rice wine.

Black rice contains a variety of bioactive substances that contribute to the high nutritional value of black rice wine (BRW). However, the dense bran layer of black rice retards the fermentation rate and reduces the dissolution of active components. Hence, this study aims to investigate the effects of pre-gelatinization (PG) before cooking and cellulase (CE) addition during fermentation on the fermentation performance of BRW and its antioxidant activity. PG combined with CE treatments (PGCE) increases the alcohol content, free amino acid content, volatile flavor content and total antioxidant activity of BRW by 90.81%, 15.36%, 38.05% and 19.56%, respectively, compared with the control group. Scanning electron microscopy, low-field nuclear magnetic resonance and texture properties analysis indicate that PG treatment increases gelatinization degree of starch during cooking, decreases bound water content in cooked black rice and promotes unbound water release. CE destroys the aleurone layer structure, facilitates the release of unbound water and the exposure of rice starch, thus increasing the reaction area and extravasation content significantly, which is beneficial to microbial growth and fermentation. Incomplete aleurone layer also promotes the dissolution of anthocyanins, phenols and other active substances, increasing the antioxidant activities of BRW. PG and CE treatments reduce the fermentation time and improve the quality of BRW by destroying the black rice structure. © 2022 Society of Chemical Industry.

Influence of structural changes of brown rice by precise polishing on in vitro starch digestibility of cooked rice grain

The relationship between the tissue structure of rice grains prepared using stepwise degrees of polishing (DOP) and starch digestibility was investigated in this study. Brown rice grains (Oryza sativa L. cv. Koshihikari) was precisely polished to 1, 3, 5, 7, and 10% (w/w) of the original weight using a pressure-type rice polisher and then cooked using a standardized cooking procedure. Although the total starch content of cooked grains had a significant tendency to increase with an increase in the DOP (77.64–84.16% db), the resistant starch content was constant between the cooked grains with different DOP (0.32–0.43% db). Cooked brown rice grains had significantly lower starch hydrolysis (65.68 vs. 89.74–96.17%) and estimated glycemic index (72.50 vs. 84.95–92.90) than polished grains after in vitro gastro-small intestinal digestion. The results revealed that starch digestibility of cooked brown rice grains was not proportional to DOP. The bran layer remained intact and covered a smaller area of the endosperm as DOP increased. In conclusion, the starch digestibility of cooked stepwise polished rice grains was affected by the bran layer on the outermost surface, which was equivalent to 1% of the weight of the brown rice grains. However, it was not affected by the ratio of the bran layer remaining on the cooked grain surface. The results of this study could contribute to the development of new agricultural machinery products that solve problems related to the control of GI of rice and rice products.

The Volatile Compounds and Aroma Profile of Some Pigmented Rice Brans After Fermentation

Pigmented rice is known to have nutritional and bioactive compounds which commonly concentrated in the bran layers. Solid-state fermentation is known to enhance the bioactive compounds of rice bran. The study aims to identify fermented rice bran’s volatile compounds and aroma attributes from some pigmented rice (Inpari 24, Saodah, Cempo Ireng and Jeliteng). The rice brans were sterilized at 121oC for 15 minutes and produced non-fermented rice bran and some of them were fermented for 72 hours at 30ºC using Rhizopus oligosporus. Both non-fermented and fermented rice brans were analysed using solid-phase microextraction-gas chromatography/mass spectrometry (GC/MS) and qualitative descriptive analysis (QDA). The result showed that a total 114 of volatile compounds were identified from fermented and non-fermented rice bran. They consisted of 14 aldehydes, 12 ketones, 14 alcohols, 15 hydrocarbons, 8 acids, 23 esters, 9 benzenes, 5 phenols, 6 furans, 2 lactones, 1 monoterpene, 1 sesquiterpene, 1 thiazole, 1 pyrazine and 1 pyridine. The aroma attributes of fermented rice brans obtained by 10 trained panellists in QDA were sweet, caramel, vanilla, grass, milky, fatty, nutty, smokey, rancid, acid, cereal, pungent, earthy and fermented. The non-fermented rice bran has the same aroma as the corresponding fermented rice bran except fermented aroma. Furthermore, Pearson’s correlation test has resulted in several positive correlations between GC-MS results and QDA. These studies indicated that fermented rice bran might increase the volatile compound of rice bran; thus, it may provide opportunities to develop the production of fermented rice bran as a functional ingredient.

Foliar Application of an Inositol-Based Plant Biostimulant Boosts Zinc Accumulation in Wheat Grains: A μ-X-Ray Fluorescence Case Study.

There has been much interest in the incorporation of organic molecules or biostimulants into foliar fertilizers with the rationalization that these compounds will enhance the uptake, or subsequent mobility of the applied nutrient. The objective of this research was to investigate the effects of an inositol-based plant stimulant on the mobility and accumulation of foliar-applied zinc (Zn) in wheat plants (Triticum aestivum L.). High-resolution elemental imaging with micro-X-ray fluorescence (μ-XRF) was utilized to examine Zn distribution within the vascular bundle of the leaf and whole grains. The inclusion of myo-inositol with Zinc sulfate, significantly increased Zn concentration in shoots in contrast to untreated controls and Zn sulfate applied alone. Foliar Zn treated plants increased Zn in grains by 5–25% with myo-inositol plus Zn treated plants significantly increasing grain Zn concentration compared to both Zn treated and non-treated controls. XRF imaging revealed Zn enrichment in the bran layer and germ, with a very low Zn concentration present in the endosperm. Plants treated with Zn plus myo-inositol showed an enhanced and uniform distribution of Zn throughout the bran layer and germ with an increased concentration in the endosperm. While our data suggest that foliar application of myo-inositol in combination with Zn may be a promising strategy to increase the absorption and mobility of Zn in the plant tissue and subsequently to enhance Zn accumulation in grains, further research is needed to clarify the mechanisms by which myo-inositol affects plant metabolism and nutrient mobility.

BIOACTIVE COMPOUNDS AND ANTIOXIDANT ACTIVITY OF PERIPHERAL LAYERS OF SOFT WHEAT GROWN IN ALGERIA DURING SEED FILLING

Wheat bran is a by-product rich in bioactive compounds. However, little is known about the arrangement, composition and secondary metabolisms of the grain outer layers during grain development. To this end, the objective of this study is to evaluate the variations in cell wall structure and chemical composition of the outer layers during the cellularization phase, the actual filling of the grain and the maturation phase. Morphological and structural aspects were evaluated by scanning electron microscopy; phytochemical study also was carried out: Extracts from the peripheral layers (CP) of wheat grain (cultivar Triticum aestivum HD1220) were analyzed to determine: Total phenols content by Folin-Ciocâlteu method, flavonoids by aluminum trichloride and sodium hydroxide method; Antioxidant power was evaluated by free radical scavenging (DPPH) and iron reduction (FRAP). The results of histological analysis showed that the outer layers become thinner during grain development, the main tissues develop and differentiate synchronously; the phenolic content ranged from 47.58± 3.23 mg GAE/g to 108.67± 10.7 mg GAE/g wheat outer layers, the wheat outer layers contained 6.96±2.61-35.297±8.68 mg EAQ/g flavonoids. The contents of total phenols (TPC) and flavonoids (TFC) increased during development; the antioxidant activity, depended on the developmental phase of the peripheral layers; the antioxidant activity studied for 70% ethanolic extracts was highest in the peripheral layers of mature grains. These results underline that the peripheral layers of wheat bran derived from maternal tissues are constituted by a superposition of different tissues and are considered as an important source of bioactive compounds.

Evaluation of microwave heating on the mechanical properties, β-glucan, and fiber content of barley kernels.

Microwave heating may affect some non-starch polysaccharides of cereal kernels. This microwave effect can be positive for functional properties and the final product. Therefore, the purpose of this work was to explore the effects of microwave heating on mechanical properties, malt extract yield, wort viscosity, &beta;-glucan of wort, and soluble, insoluble, and total dietary fiber in malting and feed barley. The barley kernels were microwave heated for 4 and 8 s and compared with a control (0 s) with no microwave irradiation treatment. The mechanical properties were measured by compressive loadings; an Environmental Scanning Electron Microscopy was used for kernel layers. &beta;-glucan content in the barley kernel and wort was measured with a Mixed Linkage beta-glucan (K-BGLU Megazyme International; Wicklow, Ireland). Insoluble, soluble, and total dietary fiber was determined using 32-07 of AACC method. The thickness of barley kernel bran layers was related to the mechanical properties. The modulus of elasticity decreased after 4 s of heating but increased after 8 s. Irradiation affected non-starch polysaccharides, such as &beta;-glucan and fiber. &beta;-glucan decreased after 4 s as did wort viscosity. The insoluble and total dietary fiber followed the same trend as &beta;-glucan, but the soluble fiber content increased with prolonged microwave heating. A few seconds of microwave heating is enough to increase barley&rsquo;s value in the brewing industry and improve health benefits due to minor changes in the biochemical grain components.

Overview of the Composition of Whole Grains' Phenolic Acids and Dietary Fibre and Their Effect on Chronic Non-Communicable Diseases.

Chronic non-communicable diseases are the major cause of death globally. Whole grains are recommended in dietary guidelines worldwide due to increasing evidence that their consumption can improve health beyond just providing energy and nutrients. Epidemiological studies have suggested that the incorporation of whole grains, as part of a healthy diet, plays a key role in reducing one’s risk for cardiovascular diseases (CVDs), obesity, type 2 diabetes (T2D) and cancer. Phenolic acids and dietary fibre are important components found in whole grains that are largely responsible for these health advantages. Both phenolic acids and dietary fibre, which are predominantly present in the bran layer, are abundant in whole-grain cereals and pseudo-cereals. Several studies indicate that whole grain dietary fibre and phenolic acids are linked to health regulation. The main focus of this study is two-fold. First, we provide an overview of phenolic acids and dietary fibres found in whole grains (wheat, barley, oats, rice and buckwheat). Second, we review existing literature on the linkages between the consumption of whole grains and the development of the following chronic non-communicable diseases: CVDs, obesity, T2D and cancer. Altogether, scientific evidence that the intake of whole grains reduces the risk of certain chronic non-communicable disease is encouraging but not convincing. Based on previous studies, the current review encourages further research to cover the gap between the emerging science of whole grains and human health.

Distribution of phenolic compounds and antioxidant activities in layered grinding wheat flour and the regulation effect of nitrogen fertilizer application

<p id="C3">Clarifying the distribution of phenolic compounds in layered grinding wheat flour and its response to nitrogen fertilizer application would provide useful information for wheat quality improvement and high-quality cultivation. Two wheat cultivars, purple wheat (Jizi 439) and white wheat (Xinhuamai 818), were planted with two nitrogen application rate (HN, N 210 kg hm^-2; LN, N 105 kg hm^-2) in Zhengzhou and Yuanyang experimental sites during growing period in 2019 and 2020. The mature grains were ground into five milling fractionations (LY1, LY2 LY3, LY4, and LY5) from the bran layer to the endospermic layer by layered grinding, and the total phenolic content (TPC), the total flavonoids content (TFC), and the anthocyanin content (AC), and their antioxidant activity were determined. The results showed that the TPC, TFC, AC, and antioxidant activity (TEAC, FRAP) in free phenols and conjugated phenols extracts decreased from the outer layer flour fractionation to the inner layer flour fractionation. The purple wheat, named as Jizi 439, had a higher antioxidant content and antioxidant activity than white wheat (Xinhuamai 818), but the difference between the two cultivars displayed a decreasing trend from the bran layer flour fractionation to endosperm layer flour fractionation. The TPC, TFC, and AC of LY1 to LY3 flour fractionation increased with the increase of nitrogen fertilizer application except for TPC of LY1 in Yuanyang. However, the contents of total phenolics and total flavonoids of LY4 to LY5 flour fractionation had a weak response to nitrogen fertilizer application. The content of ferulic acid accounted for more than 93% of the TPC in wheat grains and had a higher value under low nitrogen condition. In conclusion, purple wheat had higher antioxidant substances such as phenolics than white wheat, and the difference between purple wheat and white wheat decreased with the deepening of grinding degree. The content and activity of antioxidants in the outer layer flour fractionation were significantly responsive to nitrogen regulation, and the content increased with the increase of nitrogen.

Marker-Assisted Backcrossing (MABc) to Improve Eating Quality with Thin Seed Coat and Aleurone Layer of Non-Glutinous Japonica Variety in Rice.

Brown rice is composed of rice bran, pericarp, seed coat, and aleurone layers, and the rice bran layer contains a large number of substances useful for the human body, such as dietary fiber, α-tocopherol, α-tocotrienol, and vitamins. However, more than 90% of these substances are removed when polished, and white rice has the disadvantage of losing food-related ingredients, such as umami-related amino acids, when compared to the unpolished group. In this study, we tried to develop new breeding lines with a thinner seed coat and aleurone layer to provide high eating quality with softer chewing characteristics and processability in rice grain. We detected an SNP for foreground selection for the backcross population by comparing genome sequences between Samgwang and Seolgaeng and developed high eating quality brown rice breeding lines by applying marker-assisted backcrossing (MABC) breeding programs to backcross populations between Samgwang and Seolgaeng using KASP markers. SNP markers for foreground selection were identified to improve eating and processability through SNP mapping of Samgwang and Seolgaeng with SSIIa as a target gene in this study. Line selection according to genotype of KASP markers was successful in BC1F1 and BC2F1 generations, with the recurrent parent genome recovery ratio ranging from 91.22% to 98.65%. In BC2F1 seeds of the selected lines, thickness of the aleurone layer was found to range from 13.82 to 21.67 μm, which is much thinner than the 30.91 μm of the wild type, suggesting that selection by MABc could be used as an additional breeding material for the development of highly processed rice varieties. These lines will be useful to develop new brown rice varieties with softer chewing characteristics and processability in rice grain.

In vitro gastric digestion and emptying of cooked white and brown rice using a dynamic human stomach system

In this study, a dynamic in vitro human stomach system was employed to elucidate the influence of structural differences between white and brown rice on gastric emptying and starch digestion. The evolution of gastric digesta particle size distribution, pH, viscosity and starch hydrolysis was investigated during digestion. Due to the protective effect of the outer bran layer against structural breakdown, brown rice showed higher pH buffering capacity, larger digesta particle size and greater rheology, resulting in a delayed gastric emptying and consequently, lower starch hydrolysis in an overall starch digestibility in the stomach than the white rice. The current study has provided quantitative evidence regarding the importance of macrostructure (i.e. the bran layer) in rice gastric digestion that may further impact intestinal absorption. Meanwhile, the particle size was significantly smaller in the digesta emptied out of the stomach in both white and brown rice throughout the digestion compared to that retained in the stomach. This demonstrates an effective size reduction and sieving efficiency exhibited by the in vitro system. It is practically meaningful to use the in vitro system to track the dynamic changes in structural and physicochemical properties of food materials during digestion in the stomach.