β-D-galactosidase was partially purified to homogeneity from persimmon (Diospyros kaki Thunb. cv. Tonewase) fruit. The enzyme of G-II fraction was purified 38. 1-fold with a total yield of 14.6%. The molecular weight of native β-D-galactosidase was estimated to be about 120kDa by ND-PAGE. After SDS-PAGE of the enzyme electroeluted from native gels, two subunits with estimated molecular masses of 35kDa and 46kDa were observed. The optimum pH of the enzyme activity was found to be pH5.0, and the enzyme stable in the range of pH 5-8.

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Water activities of generic commercial white bread were determined by various measurement systems. Samples were prepared with consideration of their water adsorption or desorption history, and moisture contents were controlled in the range of 0-48% (wet-weight basis) by using desiccators with various salt solutions and phosphorus pentoxide. Three types of measurement systems were used : an electronic semiconductor sensor, the equilibrium weight measurement method and the proximity equilibration cell method. Measurement temperatures were 10, 20, 30 and 40°C, and the water activity range was 0 to 1. Isothermal sorption curves of white bread were the sigmoid type and appeared to represent moisture sorption hysteresis. In the measurement systems, the equilibrium weight measurement method obtained comparatively good results over a large range. The values obtained were used to evaluate the conformity of some adsorption equations. The adsorption equations used were the GAB and D-A equations. Both equations showed comparatively good conformity.

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Gelatinization of starch is essential in order to saccharify starch by amylase. Starch is gelatinized by heat-treatment, which requires a lot of energy. This study investigated the possibility of gelatinization of starch by high-pressure treatment, which was to make a better alternative to heat-treatment with respect to energy conservation. Potato and wheat starches were used in this study. Decomposition of potato starch by amylase accelerated after pressure treatment over 600MPa, while that of wheat starch accelerated over 400MPa. The transition enthalpy decreased at the pressure intensity, where the decomposition of starch accelerated by amylase. Although, the polarized light of small starch grains remained, the polarized light of large grains disappeared after high-pressure treatment. The result shows that the crystal structure of small grains in starch is much stronger than that of large grains. These results clearly show that the decomposition of starch by amylase accelerate after high-pressure treatment because of the crystallinity of starch changed by high-pressure treatment.

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This study aims to establish a practical procedure of fresh-cut cabbage disinfection with electrolyzed acidic water. The ratio of fresh-cut cabbage weight to treatment water volume and treatment duration were compared between electrolyzed acidic water and sodium hypochlorite solution as a conventional disinfectant to define the conditions of equal bactericidal effects. The time-dependent change in trihalomethane content was measured with fresh-cut cabbage treated with electrolyzed acidic water or sodium hypochlorite solution. The sodium hypochlorite solution treatment resulted in constant detection of approximately 0.05mg/kg of chloroform throughout the 72-hour storage, but no trihalomethanes were detected even immediately after the electrolyzed acidic water treatment. In the sensory evaluation, more than half of the thirty panelists detected abnormality in the odor and taste of cabbage immediately following the sodium hypochlorite solution treatment, whereas not more than one panelist detected abnormality even immediately after the electrolyzed acidic water treatment. After 60-minute storage following the sodium hypochlorite solution treatment, not more than two panelists detected abnormality in the odor and taste. This clearly indicates that abnormality in odor or taste is not detectable even in presence of residual trihalomethanes. Electrolyzed acidic water can provide an effective treatment without producing trihalomethanes or causing detectable abnormality in odor or taste even if used on foods to be immediately supplied to consumers.

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In mature green bananas before ripening, 103mg/100g of polyphenol compounds were contained in the pulp and about 60% of those polyphenol compounds have a MW above 2×10⁵ and an astringency. These high molecular weight polyphenol compounds produced cyanidin, delphinidin and catechin on hydrolysis with HCl and were proanthocyanidins consisting of leucoanthocyanidin and catechin. The changes in polyphenol compounds during ripening have been studied with separating by ultrafiltration and ion-exclusion chromatography and the result showed that the polyphenol compounds with a MW above 2×10⁵ and an astringency disappeared during ripening. However, no change was seen in those polyphenol compounds with a MW below 2×10⁵. These results suggest that the disappearance of astringency by ripening treatment is resulted from the polymerizing insolubilization of polyphenol compounds with a MW above 2×10⁵, the astringent components.

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Influence of some food samples of which have different levels of texture such as hardness, elasticity and chewiness on masticatory muscle activities during chewing of female young adults (54 panelists; 19 to 23 years old, average of 20.5 years old) was investigated. The texture of food samples was measured by a tensipresser. The food samples with different texture properties were selected as follows : cooked milled rice, kamaboko, cooked brown rice, peanut, pork chop, octopus boiled and seasoned, edible burdock boiled, takuan (pickled Japanese radish) and surume (dried squid). The sum of the proportion of amplitudes for temporal and masseter muscles were calculated from the electromyograms recorded. Relationship between the masticatory muscle activities on chewing 9 food samples and the texture of these foods was evaluated by regression analysis. (1) The difference between food samples was observed in terms of sum of the proportion of amplitudes for temporal and masseter muscles indicating that the sum of the proportion of amplitudes for temporal and masseter muscles could be a useful index of masticatory muscle activities. (2) The prediction formula of sum of the proportion of amplitudes for temporal and masseter muscles were obtained from the chewiness of explanatory variable (p<0.01, respectively). It was suggested that masticatory muscle activities were dependent on chewiness in the texture of foods.

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Identification of food materials based on DNA information are developed. These procedures include usually Polymerized Chain Reaction (PCR). However, it was difficult to check quality of extracted DNA for above experiment because of few methods. In this study, the possibility of PCR amplification of three genes using extracted DNA was researched. The region of 16S rDNA and 18S rDNA, and ITS region were used. As a result, the region of 18S rDNA was best for checking quality of extracted DNA because this region was amplified in high annealing temperature and amplified products in various organisms were same molecular weight.

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