The artificial digestibility of cooked rice and the structural properties of the endosperm starches of 11 cleaned rice cultivars bred in Japan were examined in vitro. The artificial digestibility was examined in vitro by analyzing the amount of free glucose after the cooked rice was treated by digestive enzyme. The structural properties of the endosperm starch were estimated by analyzing the contents of the apparent amylose and the Fr.A(DP6-12) of the starch. Digestibility of sugary rice, Ayunohikari, was the lowest of 11 rice cultivars including low-, medium-, high-amylose cultivars. The contents of apparent amylose and the Fr.A(DP6-12) of Ayunohikari endosperm starch were 21.8% and 34.6%, respectively. The factor of the inhibitive effect of digestion of cooked rice of Ayunohikari could not be well explained by the structural properties of the endosperm starch. Additionally, we found that the shape of cooked rice of Ayunohikari was maintained after digestion test. It was suggested that Ayunohikari had the resistant structure, because the inhibitive effect of digestion disappeared by crushing the rice grains. We also speculated that the resistant structure was related to the endosperm cell wall.

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Kurozu is brewed rice vinegar which has been traditionally produced in Kagoshima prefecture, Japan. When Kurozu which was concentrated by decompression and whose acetic acid was removed are orally administered to mice for 21 days, their splenic natural killer (NK) activity was significantly enhanced. This concentrated Kurozu was subjected to Sephadex G-25 gel filtration to obtain 4 fractions. The 1^st fraction having the largest molecular weight (hereinafter, Fractionated-Kurozu) has much sugar and the main components of the sugar were mannose and glucose. After sarcoma-180-bearing mice were orally administered fractionated-Kurozu for 16 days, the enhancement of the tumor was suppressed. On 3 days after inoculation, the NK activity and cytokine productions were significantly enhanced by feeding them the fractionated-Kurozu. These results suggested that Kurozu had antitumor activity and that the antitumor mechanism might be related to immunostimulation activities through the increase of NK activity and cytokine productions.

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Frozen surimis of arabesque greenling (AG), walleye pollack (WP) and their mixture (AG+WP) were thawed and mixed with 0∼2/3 times its volume of water and 0∼3% albumen powder (AP), and ground with 3.0% NaCl(w/w). The salt-ground meat was preheated at 25°C for up to several hours, and heated at 90°C for 30 minutes to obtain the heated gel. The relation of the physical property of the heated gel and the concentration (C) of the total protein (surimi+albumen) of the heated gel was investigated. The results are as follows : 1) The setting gel was obtained from WP and (AG+WP) but not from AG. 2) The exponential relation between C and the breaking strength (BS), (BS=k·Cⁿ k, n=const.) of the heated gel obtained from the surimi of AG was virtually unchanged by addition of AP, whereas the exponential relation of the heated gel obtained from WP and (WP+AG) with AP was evidently different from those formed without AP. 3) The highest value of the breaking strain (bs) of the heated gel without AP was almost similar in level with that formed with AP, although the bs value varied depending on fish species used for a material of surimi of the heated gel. The results suggested that the heated gels formed with setting and those without setting proceeded in different mechanisms in the heat-induced gel formation made of surimi and protein with AP.

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It is necessary for rice flour breads to become popular to increase the consumption of rice and to avoid the risk of tight supply of wheat. To improve the poor quality of rice flour breads, the effect of lipid and emulsifier on the bread-making quality was investigated. The quality of bread made from rice and wheat flour blend was evaluated by the specific volume, the hardness of the crumb, the staling during preservation and a sensory test. Bread made from wheat and rice flour blend (150g/50g)containing 21∼31g of butter had almost the same quality as bread made from wheat flour alone. Rice bread made from nonglutinous rice flour had better quality than the one made from glutinous rice flour. The butter showed both the largest specific volume and the largest suppression effect of the staling during preservation among the tested lipids. When we have found that the specific volume of breads increased in proportion to the total amount of saturated and monounsaturated fatty acids in the added lipids and that the solid lipids are desirable. Monoglyceride which was added as an emulsifier to the rice blend bread containing 21g of butter showed some effects to depress the staling, but sucrose fatty acid esters and lecithin did not improve the physical properties of the bread made of rice flour. A difference of the tastes between the wheat flour bread and the rice flour blend bread was not recognized in the sensory test by the senior college students.

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Useful and peculiar hydroxymethoxyflavones are included in peels of Citrus sudachi Hort. ex Shirai. However, the peels are not yet reused and disposed of as industrial refuse. In this study we used a microwave (MW)-assisted irradiation method which is efficient to extract bioactive flavones from dried peels of C. sudachi. A mixture of sudachitin (4′,5,7-trihydroxy-3′,6,8-trimethoxyflavone) and demethoxysudachitin (4′,5,7-trihydroxy6,8-dimethoxyflavone) was obtained in methanol in 0.18% yield and flavone glycosides were obtained in the water phase after MW was irradiated to the dried peels of sudachi in methanol for 10 to 12 minutes under reflux. MW-assisted hydrolysis of the glycosides with hydrochloric acid gave sudachitin in 0.42% yield. In methylation of sudachitin using dimethyl sulfate, sudachitin was quantitatively converted into nobiletin (3′,4′,5,6,7,8-hexamethoxyflavone) by irradiating MW to sudachitin for 30 min. Extraction of flavones from the peels of sudachi and their methylation using MW irradiation is a more rapid, efficient, and more eco-friendly method than extraction and methylation using a conventional thermal heating one.

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Freeze-thaw infusion (FI) is a technique rapidly to impregnate enzymes and so on into food materials. FI produces soft food materials retaining their original shape. We investigated the digestibility of softened lotus roots treated with FI using an artificial digestion test and administrating the lotus roots into the rats' stomachs. In the artificial digestion test with pancreatin for 3h, the amount of insoluble solids of softened lotus roots treated with FI was artificially digested 4.3±0.1 (g/100g). The amount of the insoluble solids obtained by artificial digestion for 9h of the controlled samples without FI was 6.7±0.1 (g/100g). The amount of insoluble solids after artificial digestion correlated with the degree of hardness of the original lotus roots (rs=0.95, p<0.01). According to this result, it was deduced that the materials softened with FI increased the digestible amount of materials and shortened the digestion time. As a result of the gastric administration in rats, the samples treated with FI had a higher residual ratio of gastric soluble pigments, and a smaller modal diameter of gastric insoluble solids compared with the controlled samples. These results suggest that the softened materials are expected to delay the rate of gastric emptying of soluble materials and to prevent the feeling of fullness in the abdomen. These results also suggest that the softened food materials treated with FI can enhance digestibility.

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We investigated the effect of edible green algae Monostroma nitidum on glycemic responses after oral administration of various saccharinity agents. Male Wister rats (6-8 weeks old) were administered 2g/kg b.w. glucose, sucrose, maltose or soluble starch with or without 0.2g/kg b.w. M. nitidum powder. M. nitidum significantly inhibited the increment of plasma glucose level (p<0.01). When we examined the three fractions of M. nitidum, that is to say, MeOH-soluble one, hot water-soluble one (crude rhamnan sulfate extract) and insoluble one on glycemic responses, rats administered crude rhamnan sulfate extract showed significantly lower plasma glucose level than the controlled group (p<0.01). Furthermore, the effects of M. nitidum and rhamnan sulfate on the postprandial increase in blood glucose level were evaluated in healthy adults. The significant deduction of the blood glucose level was observed at 30 minutes after the intake of M. nitidum powder or crude rhamnan sulfate extract compared to the controlled ones (p<0.05). These results suggests that the M.nitidum and rhamnan sulfate are useful for diabetes mellitus.

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[in Japanese]

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