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Recently, global warming has led to an increase in chalky rice grains. This has consequently resulted in the deterioration in quality of rice products. Although we previously reported that hard water, rich in Ca, is useful for the quality improvement of high-temperature-damaged rice grains, the mechanism was not elucidated sufficiently. Therefore, we used various kinds of rice cultivars, from waxy to high-amylose ones, for soaking and boiling in hard water and compared physical and chemical properties of the products. It was shown that the degree of quality improvement, such as final viscosities in pasting property, and textural properties of boiled rice, was more remarkable for high-amylose rice than low-amylose rice. As we found that the phosphorus contents showed positive correlations with amylose and long chains of amylopectin, we estimate that the effects are mainly due to binding of calcium and phosphorus. Because that high-amylose or long-chain-rich amylopectin rice cultivars showed high calcium contents in rice products, these rice cultivars would be very useful to supply calcium through dietary intake via hard water cooking.

Background: Endothelial dysfunction is an early pathophysiological feature and independent predictor of a poor prognosis in most forms of cardiovascular disease. We evaluated the effect of brown rice crackers (BR-C) on endothelial function. Methods: Effect of heat-moisture treated (HMT) -BR-C on postprandial flow-mediated dilation (FMD) in adults with mild endothelial dysfunction was compared with that of BR-C and white rice crackers (WR-C) in 12 adults with mild endothelial dysfunction (less than 7.0% of FMD) by a randomized, single-blind, three-treatment three-period crossover trial (UMIN 000034898). Since we considered that the FMD increase was associated with the treatment of HMT-BR-C, we examined the effect of three possible factors: postprandial glucose levels, polyphenol content, and polyphenol release from the food matrix. Results: Mean pre-intake baseline FMD values of HMT-BR-C, BR-C, and WR-C were 4.9%, 5.1%, and 4.9%, respectively, and those values 1 h post-intake were 6.3%, 5.1%, and 4.8%, respectively. There was no difference in intergroup comparisons of FMD using Dunnett's multiple comparison test. There was a significant increase in FMD only in HMT-BR-C in intragroup comparisons (P = 0.042 by paired-t test). In comparison with BR-C, no significant difference was noted in the postprandial glucose level nor in the content of total polyphenols and ferulic acid derivatives in HMT-BR-C. However, the 70% ethanol extracted from HMT-BR-C contained a significantly larger amount of free and bound ferulic acids than from BR-C. Conclusion: HMT-BR-C intake increased the postprandial FMD response.

In the present paper, we investigated the characteristics of chalky rice grains generated by ripening under high temperature and compared them with whole grains. We evaluated 14 unpolished Japonica rice grains harvested in Japan in 2021, and these samples (original grains) were divided into two groups (a whole grain group and a chalky grain one). We found that not only activities of endogenous amylase and proteinase, but also cell wall-degrading enzymes, such as xylanase and cellulase, changed markedly between chalky grains and whole grains. Using rice grains blended with 30% of chalky grains as the material, we compared the sugar and mineral contents and textural properties of the rice grains soaked and boiled in either ordinary water or hard water, such as Evian or Contrex. It was shown that xylanase, in addition to amylase and proteinase, may play an important role in changing the texture of the boiled chalky rice grains. For the sake of preventing the above-mentioned deterioration in the texture of boiled grains of chalky rice, we tried to use hard water, such as Evian or Contrex, to soak and cook the chalky rice grains. It was shown that the hard water was useful for the prevention of texture deterioration of the boiled rice grains due to inhibition of the activities of endogenous hydrolytic enzymes, such as α-amylase, β-amylase, proteinase, and xylanase. Furthermore, we found that the hard water was useful in increasing the calcium absorption through the meal by 2.6 to 16.5 times.

Global warming inhibits grain filling in rice and leads to chalky grains, which are damaged in physical and cooking qualities. In the present paper, we evaluated 54 Japonica unpolished rice grains harvested in Japan in 2020, and these samples (original grains) were divided to two groups (whole grains and chalky grains). Using rice grains of 100% whole grains or those blended with 30% of chalky grains, we measured contents of sugars and amino acids, and textural properties of boiled rice grains. It was shown that the α-amylase activity and proteinase activity of raw chalky rice were significantly higher than those of whole rice grains, which led to the significant increase of low-molecular-weight sugars and free amino acids after boiling. Furthermore, hardness and toughness of the boiled rice grains were decreased markedly by blending chalky grains. The ratio of α-amylase activity of chalky grains to that of whole grains was shown to be a useful indicator for damage degree by high-temperature ripening. It became possible to estimate the degree of high-temperature damage of rice grains based on only the pasting properties of unpolished rice.

As it has been reported that type 2 diabetes mellitus increases the risk of Alzheimer’s disease, we investigated how to prevent type 2 diabetes and dementia using biofunctional boiled rice. We adopted unpolished super-hard rice (SHBR) for diabetes and wax-free unpolished black rice (WFBBR) for dementia and blended those with ordinary non-polished rice (KBR) (blending ratio 4:4:2), adding 2.5% waxy black rice bran (WBB) and 0.3% rice oil after high-pressure treatment (HPT) (WFBSK) to improve its palatability. This boiled rice is rich in dietary fiber, anthocyanin, free ferulic acid and β-secretase inhibitory activity. A randomized, parallel-group comparison study was conducted for 12 weeks with 24 subjects, using Cognitrax to evaluate their cognitive function primarily. Furthermore, as the secondary purpose, we performed a single-dose test for postprandial blood glucose and insulin secretion at the end of the human intervention test. After 12 weeks, consumers of the WFBSK rice exhibited significant improvement in language memory by cognitive test battery compared with those who consumed the control white rice (p < 0.05). Moreover, subjects who consumed the WFBSK rice had lower insulin secretion levels than those who consumed the control polished rice (p < 0.05).

Global warming has caused devastating damage to starch biosynthesis, which has led to the increase in chalky grains of rice. This study was conducted to characterize the qualities of chalky rice grains and to develop the estimation formulae for their quality damage degree. We evaluated the chalkiness of 40 Japonica rice samples harvested in 2019, in Japan. Seven samples with a high ratio of chalky rice grains were selected and divided into two groups (whole grain and chalky grain). As a results of the various physicochemical measurements, it was shown that the surface layer hardness (H1) of cooked rice grains from chalky grains was significantly lower, and their overall hardness was significantly lower than those from the whole grains. In addition, α- and β-amylase activities, and sugar contents of the chalky rice grains were significantly higher than those of the whole rice grains. The developed estimation formula for the degree of retrogradation of H1 based on the α-amylase activities and pasting properties, showed correlation coefficients of 0.84 and 0.81 in the calibration and validation tests, respectively. This result presents the formula that could be used to estimate and to characterize the cooking properties of the rice samples ripened under high temperature.

With rice being one of the most important crops worldwide, rapid and objective quality evaluation methods based on physicochemical measurements of rice are necessary. We compared the pasting properties of various rice samples using three different heating and cooling programs (maximum temperatures were 93, 120, and 140 °C, respectively) in a newly developed high-temperature-type Rapid Visco Analyzer (RVA, RVA 4800). Furthermore, we investigated the relationship between the different pasting properties measured by the three programs, with starch microstructure measured by iodine scanning analysis, the physical properties of the cooked rice measured by a Tensipresser after 2 h at 25 °C or after 24 h at 6 °C, and prolamin ratio measured by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The consistency value (final viscosity–minimum viscosity) yielded by a new program of maintenance for 2 min at 120 °C using RVA 4800 had a higher positive correlation with retrograded surface hardness H1(R) (r = 0.92), retrograded overall hardness H2(R) (r = 0.90), and the absorbance at λmax (Aλmax) of cooked rice (r = 0.88) and resistant starch (r = 0.80) than those by the conventional program at 93 °C. We developed estimation formulae for H1(R) for various kinds of rice, of which the determination coefficient was 0.86. It led to an easy and rapid assay method for the cooking properties of the various rice samples.

The objective of this study was to characterize the endosperm starch in rice that ectopically overexpressed the α-amylase. Transgenic rice plants, transformed with cauliflower mosaic virus 35S promoter driven AmyI-1 (35S::AmyI-1) and AmyII-4 (35S::AmyII-4), and 10 kDa prolamin promoter driven AmyI-1 (P10::AmyI-1), were cultivated under standard conditions (23 °C, 12 h in the dark/ 26 °C, 12 h in the light), and brown grains were subsequently harvested. Each grain displayed characteristic chalkiness, while electron microanalyzer (EPMA)-SEM images disclosed numerous small pits on the surface of the starch granules, attributable to α-amylase activity. Fluorescence labeling and capillary electrophoresis analysis of starch chain length distribution revealed no significant alterations in the starches of 35S::AmyI-1 and 35S::AmyII-4 transgenic rice compared to the wild-type. Conversely, the extremely short α-glucan chains (DP 2-8) exhibited a dramatic increase in the P10::AmyI-1 starch. Rapid visco-analyzer analysis also identified variations in the chain length distribution of P10::AmyI-1 starch, manifesting as changes in viscosity. Moreover, ¹H-NMR analysis uncovered dynamic modifications in the molecular structure of starch in rice grain transformed with P10::AmyI-1, which was found to possess unprecedented structural characteristics. [ABSTRACT FROM AUTHOR]

This study reports that black rice bran (BRB) intake for 50-52 consecutive weeks (~12 months) reduces tau phosphorylation with a concomitant activation of insulin signaling and subsequent PI3K/AKT pathway in the brain of aged normal mice. BRB holds promise for preventing the formation of neurofibrillary tangles consisting of hyperphosphorylated tau, a pathological hallmark of Alzheimer's disease. [ABSTRACT FROM AUTHOR]

In this study, we investigated the starch, pasting, thermo-physical, and iodine absorption spectrum properties of Chou 2418, a new amylopectin long-chain (ALC) rice cultivar developed by crossing a high amylose rice cultivar Koshinomenjiman and amylose extender mutant rice cultivar EM10. Chou 2418 exhibited high apparent amylose content, high pasting temperature, and low breakdown viscosity. The iodine absorption spectrum indicates that Chou 2418 contains long-chain glucans of amylopectin and also has high amylose content. Boiled rice grains of Chou 2418 contained more resistant starch (RS) than those of high amylose rice cultivars. The RS content of Chou 2418 rice grains increased following the retrogradation of starch granules, and the grains became hard and non-sticky. The RS content of Chou 2418 was 25 times higher than that of Koshihikari, the most popular rice cultivar. Taken together, these data suggest that Chou 2418 is a suitable raw material for bio-functional foods that help prevent diabetes. [ABSTRACT FROM AUTHOR]

The "Koshitanrei" rice cultivar is grown and widely used for sake brewing in Niigata Prefecture; however, the starch characteristics of this cultivar have not yet been elucidated. Therefore, we investigated the influence of starch properties on the gelatinization properties and digestibility of this cultivar, which are very important in sake production. Starches of rice samples milled to 60 % yield from "Koshitanrei," "Yamadanishiki," "Gohyakumangoku," and "Koshiibuki" were subjected to iodine colorimetric scanning analyses and pasting properties were investigated using a rapid viscosity analyzer. The correlation between iodine absorption and digestibility was analyzed following steaming of the rice samples. The findings of our study showed that the maximum wavelength of the iodine absorption curve (λCmax), which is derived from the chain length distribution of amylopectin, of Koshitanrei was the same as for Yamadanishiki, followed by Gohyakumangoku and Koshiibuki. Further, we found that λmax was significantly correlated with enzyme digestibility. The results of our study show that enzyme digestibility can be estimated by a simple evaluation method, that is, iodine absorption scanning analysis. [ABSTRACT FROM AUTHOR]

Heat moisture treatment (HMT) is a processing method used to improve the physicochemical properties of starch. Here, to inform technology with respect to increasing resistant starch (RS) in rice, three rice flours with different starch structures--namely, Koshihikari, Koshinokaori, and Goami2 (GA2)--were treated at 120 °C and 14 %-26 % humidity and compared with cornstarch. HMT increased the RS content of all specimens, with GA2 showing a marked RS increase up to 11.0%. HMT also increased the gelatinization temperature (Tget) of all samples, as shown by differential scanning calorimetry, and RS content tended to increase with increasing Tget values. As shown by the increase in relative crystallinity by X-ray diffraction and change in the iodine absorption spectrum, HMT easily changed the starch structure in GA2, leading to increased RS. These results support GA2 as a suitable rice cultivar for bio-functional rice products such as low glycemic index foods. [ABSTRACT FROM AUTHOR]

In general, giant embryo rice has a lower germination rate and shows non-uniformity in seedling emergence. We attempted to determine suitable pH and temperature conditions for germinating the giant embryo rice cultivar Koshiguruma, grown in Niigata Prefecture, in combination with red onion extract. We also examined metabolic changes in the grains that could have important human health benefits. Koshiguruma showed a higher germination rate (1.1 times) when germinated with red onion extract for 24 h at 37 °C and contained more gamma aminobutyric acid (1.7 times) than when germinated with water. In addition, germination of Koshiguruma in combination with polyphenols imparted antioxidant capacities. Thus, we have established methods for improved cultivation of giant embryo rice, which may have important human health benefits upon consumption. [ABSTRACT FROM AUTHOR]

The amylopectin long-chain rice “Konayukinomai” (MAI) is high in resistant starch (RS). In this study, we confirmed that fine rice flour for bread making could be obtained using MAI, and compared the results to the highamylose cultivar “Koshinokaori” (KOR) and the conventional cultivar “Koshihikari” (HKR). MAI bread contained larger amounts of RS and slowly digestible starch (SDS) than that of HKR or KOR, and the RS content of MAI was easily changed by retrogradation and re-gelatinization of the starch. In a clinical trial with healthy volunteers, MAI and KOR breads could prevent abrupt increases in blood glucose and showed low glycemic index (GI) values compared to HKR bread. From the above results, we propose that SDS and RS prevent increases in blood glucose, and consider MAI to be a promising rice cultivar as a nutraceutical food material for the prevention of lifestylerelated diseases. [ABSTRACT FROM AUTHOR]

The article discusses a study for developing a formulae in estimating amylose content, amylopectin distribution and starch content on the iodine absorption curve of rice starch. Topics discussed include characterization of the starches of rice cultivars, evaluation in the relationship between their iodine absorption curve, apparent amylose content (AAC), and pasting property, and proposition of the novel index, "new λmax" using the wavelength at which absorbance becomes maximum.

The article offers information on the improved palatability and bio functionality of super-hard rice by soaking them in a Barley-Koji Miso suspension. Topics discussed include effects of soaking mutant rice cultivars in a miso suspension, low glycemic index (GI) and procedure for making Koji and Miso. It also discusses Moisture absorption index (MAI) of rice, α-Amylase activity of miso and rice grains.