The lowest amount of stimulus to trigger a sensation is called a threshold. Although previous studies have demonstrated thresholds of various tastants, most of them were measured in a simple water solution. In this study, we measured absolute thresholds of sweet (glucose, sucrose, high-fructose corn syrup (HFCS-55), and mirin) and umami (monosodium glutamate (MSG) and nucleotides) tastants in soy sauce as a complex solution system. The thresholds for glucose and MSG were 1.8% and 1.9% in soy sauce, which were 3.2- and 73-fold more than those obtained in water solution, respectively. These results suggest that the appropriate amount of tastant to add to soy sauce cannot be accurately estimated using a simple water solution. The relative concentrations of sweet tastant thresholds are as follows : glucose> HFCS-55> mirin> sucrose. The umami tastant threshold for MSG was 130-fold that for nucleotides. Thus, supplemented tastants appear to be more influential on thresholds when these components are not naturally found in soy sauce and when they are combined in a more complex mixture. We also showed that the difference in thresholds for glucose between soy sauce alone and soy sauce on tofu was 2.3-fold that for MSG. Therefore, consideration of the types of foods on which soy sauce is used is important when developing soy sauce supplemented with tastants.

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A total of 24 samples of rice flour were prepared from 16 different types of rice for analyzing the crude protein, amylose, damaged starch and particle size composition. The particle size of all rice flour samples was over 90% at the 200 mesh passage, but the particle size compositions differed among the rice types. Hokuriku 166 showed a higher 300 mesh passage proportion than other rice types and trends of lower damaged starch content. Regarding the physical properties of gluten-mixed rice flour, the farinograph water absorption rate differed among the rice types, showing a correlation to the amylose content. Specific volume and shape of the rice flour bread also differed among the rice types, with the amylose content being related to the viscogram property of the gluten-mixed rice flour. About 25% amylose content of rice flour was estimated to result in the largest specific volume of rice flour bread. Rice flour bread hardness was also correlated to the amylose content. The hardness of all the rice flour breads increased relative to storage time, but the rate of bread hardening differed among the rice types. In the floury and low glutelin rice types, low values of bread hardness and hardening rate were found in comparison with normal rice flour bread which had equivalent amylose and protein contents. Therefore, protein and element composition of the rice appears to affect the bread properties. The amylose rice cultivars containing about 15 to 25% amylose content are the most suitable for baking rice flour bread.

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Anti-obese effects of tea leaf powders were compared in mice who consumed ‘benifuuki’, a tea cultivar that contains unique methylated catechins such as epigallocatechin-3- O-(3-O-methyl) gallate (EGCG3”Me), and ‘yabukita’, a popular tea cultivar in Japan that lacks methylated catechins. For 5 weeks, four groups of 12-week-old male C57BL/6J mice (n=10 per group) were fed either high-fat diets with and without the addition of 2% benifuuki or 2% yabukita tea leaf powder ; for a non-obese control group, mice were fed a low-fat diet with no additive. The body weight and food intake were recorded for each mouse 3 times a week. On the last day of the experiment, the mice were sacrificed to determine the final weight of white adipose tissue as well as blood levels of lipid metabolism-related components. The hot-water extract of benifuuki, an ingredient useful for industrial applications, was similarly examined in mice for anti-obese effects and dose dependency by a single daily oral administration of 25, 50 and 100 mg total catechins per kg body weight. The mice fed a high-fat diet containing 2% benifuuki powder showed significant decreases in body weight, adipose tissue weights and plasma leptin concentration, compared with those fed a control high-fat diet with no additive. On the other hand, the mice fed a high-fat diet containing 2% yabukita powder showed less anti-obese effects, with the only significance in subcutaneous fat weight. A single daily administration per os of benifuuki extract to mice that were fed a high-fat diet ad libitum showed anti-obese effects in a dose-dependent manner. The results indicated that benifuuki had much higher anti-obese effects than yabukita, and was dose dependent. The strong anti-obese activity of benifuuki may be ascribed to the unique methylated catechins (primarily EGCG3”Me) contained exclusively in this cultivar, whose fractional absorption and stability in blood are much higher than EGCG.

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The molecular mechanism underlying high anti-obese effects of ‘benifuuki’, a tea cultivar that contains unique methylated catechins such as epigallocatechin-3-O-(3-O-methyl) gallate (EGCG3”Me), was explored. This cultivar was then compared with ‘yabukita’, a popular tea cultivar that lacks these methylated catechins. (1) The comprehensive gene expression in the perirenal adipose tissue of mice (12-week-old male C57BL/6J) was examined by DNA microarray analysis, following consumption of either high-fat diets with and without the addition of 2% benifuuki or 2% yabukita leaf powder. (2) In cultured 3T3-L1 cells, EGCG, EGCG3”Me and caffeine were compared for their inhibitory effects on the intracellular fat accumulation as well as on cell differentiation from precursor to mature adipocytes. (3) Time-dependent changes in EGCG and EGCG3”Me plasma concentrations were examined in catheterized rats following oral administration of benifuuki extract under an overnight fasting condition. The results of the DNA microarray indicated that the anti-obese effect of benifuuki may be ascribed to the inhibition of fat accumulation in adipocytes via the downregulation of enzyme expression associated with both the synthesis and β-oxidation of fatty acids. The stronger anti-obese effects of benifuuki compared with yabukita may be attributed to the presence of its unique methylated catechins (primarily EGCG3”Me), whose stability in circulation is 3.2 times higher than EGCG ; however, the inhibitory activity of EGCG3”Me on fat accumulation is almost the same as that of EGCG (about 91% in terms of differentiation inhibition in 3T3-L1 cells). Thus, EGCG3”Me appears to fortify the overall anti-obese effects of benifuuki. That is, the inhibitory activity on fat accumulation through the combination of both EGCG and EGCG3”Me was 1.7 times higher than that through EGCG alone, even though the content of EGCG3”Me in benifuuki is much less than EGCG.

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Shikokumai 105 (Oryza sativa), which was bred in Shimane Agricultural Technology Center, is a black rice that contains anthocyanin pigment in its rice bran. We found that this pigment consists mainly of cyanidin-3-glucoside and peonidin-3-glucoside. As various functions in anthocyanin are well known, we measured DPPH radical and superoxide radical scavenging activity of shikokumai by colorimetry and electron spin resonance spectroscopy to examine shikokumai as a functional material. We confirmed strong activity for cyanidin-3-glucoside, which contributed to more than 55% of superoxide radical scavenging activity of the extracted pigment fraction. Protocatechuic acid contributed about 12% of the radical scavenging activity. In total, the identified pigments and protocatechuic acid contributed to 71% of all radical scavenging activity of the extracted pigment fraction.

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Breads made from rice flour have attracted attention due to the increase in consumption of rice. However, the quality of these rice flour breads is poor. To develop rice bread with high quality, we made bread using cooked rice. The bread-making quality of cooked rice bread was evaluated based on loaf height and a sensory test. Bread made from up to 30% cooked rice in wheat flour had an almost equal baking quality with that made from wheat flour alone, and its quality decreased as the amount of rice flour increased. Breads containing 10-40% cooked rice resulted in significantly higher evaluation than wheat flour breads on the sensory test, with an optimal ratio of 30% cooked rice. Crum grain, color and smell had no significant difference among the breads, except for the 20% cooked rice bread on color. Tactility and hardness were significantly higher in the 10-30% cooked rice breads, with an optimal cooked rice substitution ratio being 20%. The 30% cooked rice bread also had the highest evaluation for taste and doughiness. Evaluation of moisture and sweetness increased relative to the cooked rice substitution ratio. On the other hand, rice flour breads had no significant differences in overall sensory evaluation. Cooked rice as a sub-raw material of bread improved bread-baking quality, as well as taste and texture. The optimal substitution rate of cooked rice for wheat flour was 30%.

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