The effects of β-amylase activity and starch pasting temperature on maltose generation in steamed sweet potato were investigated using various cultivars and breeding lines. The maltose content per fresh weight of steamed roots increased to about 10 % (w/w) with β-amylase activity up to about 0.2 m mole maltose/min/mg protein, and maltose content was maintained at that level with activity up to 0.55 m mole maltose/min/mg protein. The maltose concentration showed a slight positive correlation (r≒0.38) with the starch content of storage roots and a practically negative correlation (r≒-0.53) with the starch pasting temperature, as measured by rapid visco analyzer (RVA). Neither the content nor the pasting temperature of starch showed any significant correlation with the β-amylase activity in roots. The influence of starch pasting temperature on the maltose concentration was more apparent in the storage roots with high β-amylase activity (0.2∼0.55 m mole maltose/min/mg protein) than in those with low activity (0∼0.2 m mole maltose/min/mg protein). The pasting temperature of starch isolated from the roots of “Beniazuma” and “Beniharuka” harvested in Hokkaido Prefecture was lower (about 6.9°C and 5.0°C, respectively) than in those harvested in Ibaraki Prefecture. The maltose concentration of steamed roots of the two varieties harvested in Hokkaido Prefecture was higher than those harvested in Ibaraki Prefecture ; while the β-amylase activity of the roots harvested in Hokkaido was not higher than in those from the southern part of Ibaraki. These results suggested the importance of starch pasting temperature for maltose generation by heating in sweet potato, particularly in cultivars with high β-amylase activity.

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To utilize the functional ingredients of tea leaves, we examined conditions for rapidly extracting O-methylated catechins, epigallocatechin (EGC) and theanine using a tea infuser, “Rich plus (RICH+^®)”. Nineteen mg of O-methylated catechins per cup (120 mL) could be extracted with water at 94°C in 20 seconds with stirring using 1.9 g of “Benifuuki” green tea that contained 1.7 % of O-methylated catechins by weight. Thirty-nine mg of EGC and an EGC/EGCG ratio of 2.5 could be extracted at 10°C in 30 seconds with stirring using 1.5 g of ‘Yutakamidori’ green tea in which the EGC/EGCG ratio was about one. Twenty mg of theanine could be extracted at 65°C in 20 seconds with stirring using 1.7 g of ‘Saemidori’ green tea that contained 1.4 % by weight theanine. These quantities correspond to approximately half the daily recommended intake of O-methylated catechins and EGC that the anti-allergic action and immunostimulating action have been described in the manuscripts.

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Shiro-shoyu is a type of soy sauce (shoyu) produced mainly from wheat. When raw shiro-shoyu is heated for pasteurization, the heated shiro-shoyu often clouds and produces sediment during storage. In order to prevent this phenomenon in typical shoyu such as koikuchi- and usukuchi-shoyu, raw shoyu is heated (hi-ire) to denature proteins, left to stand several days (ori-sage) for flocculation, and then filtered to remove sediment. However, the conventional refinement procedures could not sufficiently clarify the heated shiro-shoyu. The haze formed in the hi-ire contained proteins. SDS-PAGE analysis revealed protein fragmentation, suggesting the activation of internal protease by heating. The residual haze present even after both the addition of a flocculant in the ori-sage process and centrifugation was thought to gradually flocculate and eventually form secondary sediment. A commercially available protease was used in shiro-shoyu to produce a stable clarified product. Heat treatment to about 90°C with 0.2 % (w/v) or more of the protease significantly improved the clarity of shiro-shoyu after ori-sage and subsequent centrifugation. The addition of silica sol after heat treatment with the protease had the best effect on shiro-shoyu clarity. Nutrient composition of the treated shiro-shoyu was comparable to that of raw shiro-shoyu; however, heating resulted in slight darkening. When stored at 50°C for 7 days, the treated shiro-shoyu maintained its clarity, while raw shiro-shoyu contained sediment. Thus, the protease treatment is a highly effective method for manufacturing clarified shiro-shoyu.

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Ground beef in meatball form was investigated for changes in the available lysine content during simple grilling and teriyaki cooking (broiling with a mixture of soy sauce and sweet cooking rice wine (mirin)). In teriyaki cooking, a change in nitrogen content was not detected. The available lysine content had a high positive correlation with water content and color tone L^*. Along with a decrease in water content (overheating), the amino-carbonyl reaction (change to brown color) proceeded due to the liquid mixture, and the available lysine content tended to decrease at the same time. Furthermore, the rate of lysine content decrease was remarkably high in teriyaki, twice as high as that in simple grilling at 12 or 24 min.

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Considerable differences were found in the incidence of age-associated diseases and the mean lifespan between countries of similar social background. Previously, the inhibition of age-associated disease progression was considered to be attributable to anti-oxidants in foods, such as isoflavones and resveratrol. However, the results of recent studies do not support the role of anti-oxidants in the inhibition of age-associated diseases and senescence. We have reported that healthy foods such as beans, mushrooms, seafoods and vegetables, and healthy dietary traditions such as the Mediterranean diet and Japanese foods are rich in polyamines (spermine and spermidine). Polyamines are synthesized in rapidly growing cells; however, this ability decreases with aging. In addition to de novo synthesis, cells can take up polyamines from their surroundings. An important source of whole body polyamines originates in the intestinal lumen, e.g., food-derived polyamines. Polyamines in the intestinal lumen are absorbed quickly, and continuously increased polyamine intake elevates blood polyamine levels in humans and mice. In addition to the many biological activities that help protect cells and tissues from harmful stimuli, we have shown that polyamines suppress pro-inflammatory status, characterized by the suppression of leukocyte function associate antigen 1 (LFA-1) expression and pro-inflammatory cytokine production. Moreover, increased intracellular spermine from extra-cellular sources enhanced the activities of DNA methyltransferases (DNMT) and suppressed polyamine deficiency-induced genome-wide demethylation/methylation in vitro. Long-term increased polyamine intake inhibited age-associated pathological changes and suppressed abnormal genome-wide demethylation/methylation in Jc1 : ICR male mice. In addition, increased polyamine intake was associated with a decreased incidence of colon tumors in BALB/c mice after 1,2-demethylhydrazine administration. Aging is associated with decreased polyamine synthesis, enhanced pro-inflammatory status (e.g., increased LFA-1 expression), decreased DNMT activities, and enhanced genome-wide demethylation/methylation; therefore, dietary polyamine represents a valuable food element to suppress age-associated pathologies and extend the lifespan of humans.

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Hot water extracts of green soybean, Glycine max (WEGS) significantly decreased the levels of ovalbumin (OVA)-specific IgE in mice and significantly suppressed toluene diisocyanate-induced nasal mucosa secretion. An open-label human pilot study including 16 subjects with Japanese cedar pollinosis (JCP) was conducted. The symptom scores for JCP were better in the long-term WEGS intake group than in the short-term intake group. WEGS have great potential as an orally active immune modulator for the treatment of various allergic diseases. We conducted a preliminary investigation of the effects of visible light irradiation on plant extracts, and observed a strong suppressive effect on interleukin (IL)-2 expression in Jurkat cells following treatment with visible light-irradiated ethanol extract from green soybeans (LIEGS). This effect was produced only by extracts from green soybeans and not soybeans of other colors. LIEGS suppressed lipopolysaccharide-induced IL-6, IL-12, and TNF-α expression levels in human monocyte THP-1 cells in a concentration-dependent manner. LIEGS suppressed the development of atopic dermatitis-like skin lesions and reduced the dermatitis scores of NC/Nga mice.

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