Fish protein was solubilized by an acid protease in a batch reactor. Non-salted pollack frozen surimi was used as substrate. Parametric studies were carried out to determine the effects of temperature, pH, initial substrate concentration and enzyme concentration on the kinetics of solubilization. The reaction rate equation was presented from the kinetic model which was based on Michaelis-Menten type kinetics, taking account of product inhibition. Furthermore, a simple rate equation was derived by simplifying the above equation. Parameters in the rate equation were estimated by using observed data. The experimental data were in good agreement with the prediction calculated from the equations.

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The thermal gel-formation properties of muscle proteins, soybean proteins and their mixture with or without urea were examined by means of dynamic rheological measurements and SDS-PAGE. The following results were obtained. (1) In the systems of natural actomyosin and myosin, the thermal gelation was promoted by mixing soybean 11S protein in either case, and their thermal behavior was influenced by actin. (2) The gel-formation of natural actomyosin and myosin was largely suppressed by the addition of 2M urea, on the other hand, gelation of the mixture of each myofibrillar protein and soybean 11S protein was completely inhibited by the addition of 1M urea. These results indicated that hydrophobic interactions played a role in the heat-induced gelation of the single myofibrillar protein systems, while hydrogen bonds became markedly involved in gelation by mixing soybean 11S protein.

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For determining the total sulfite content in sea foods by a microbial sensor method, the conditions for decomposition of combined form of sulfite into free form by sulfuric acid were examined. The optimum sulfuric acid conc., heating temperature and heating time were determined to be 1N, 85°C and 15min, respectively. Under the optimum condition, the recovery of added sulfite from 11 kinds of sea foods was 90 to 98%. The total sulfite values measured by the microbial sensor method were coincided with those obtained by the modified Rankine's method. The sensitivity of the microbial sensor for sulfite determination was enhanced to 0.1μg/ml or g by changing a gas-permeable membrane and a sample volume. These results indicated that the microbial sensor method was applicable to the determination of the total amount of sulfite in various sea foods.

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Antioxidative activities of isoflavones in fermented soybeans (Mamemiso and Tempe) were studied. HPLC of methanol extracts obtained from each samples was carried out by a reversed-phase method with a linear gradient system of methanol (20-80%) as an eluent. Defatted soybeans contained almost only isoflavone glycosides. Tempe fermented for 40h at 31°C was shown to contain both isoflavone glycosides and their aglycones. Extracts of Mamemiso fermented for 30 days at 30°C contained the aglycones. As a result of the measurement of isoflavones in Mamemiso profiled by HPLC, their glycosides were shown to decrease and their aglycones to increase during fermentation for 12 days followed by no change in each isoflavone during storage for 12-30 days. β-Glucosidase activity seemed to be maximum in Mamemiso fermented for 12 days. Mamemiso fermented for 30 days was more antioxidative against oxidation of linoleic acid than that fermented for 12 days. These results suggest that the stronger antioxidant activity of Mamemiso, fermented defatted soybeans, might be caused by the cooperative effect of the isoflavone aglycones and peptides produced by the hydrolysis of soybean protein. Furthermore, comparative antioxidant activity of each sample using the carotene bleaching method and TBA method showed an order of Mamemiso>Tempe>defatted soybeans.

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The 2, 4-dinitrophenylhydrazine (DNP) method has been widely used for the determination of ascorbic acid, however, this method is complicated and time consuming, and is influenced by the presence of various compounds, such as sugars (glucose, fructose and sucrose etc.) and keto acids. In the present study, dehydroascorbic acid osazone was separated from sugar osazones on TLC plate and determined by a TLC densitometer. This method was applied to the determination of ascorbic acid in some vegetables and fruits. In comparison with the conventional DNP method, the present method is simple and more rapid. Ascorbic acid samples can be measured both qualitatively and quantitatively with a comparatively high sensitivity (10^-9 gram order) in the proposed procedure.

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We tried to keep foods fresh using yeasts which consume oxygen in a food package and generate ethanol into it. Twenty-two sugar tolerant yeasts were isolated from foods and related materials, and 5 of them were ethanol resistant yeasts. As a result of examination, we obtained two strains, S-5 and S-22. They were immobilized in agar, locust bean gum, and xanthan gum with a growth medium. The immobilized medium was enveloped by a high gas permeable film. We incubated envelop-packed foods which inoculated Escherichia coli and Aspergillus oryzae and immobilized medium. As a result, the growth of inoculated E. coli and A. oryzae in foods was highly inhibited.

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Natto was prepared from soybeans cooked under a steam pressure of 1.5kg/cmcm² for various periods ranging from 1 to 60min, and sensory evaluation, hardness, enzyme activities, components and stringiness of viscous substances of Natto samples were investigated. The hardness of Natto decreased with soybean cooking time. The color of Natto samples prepared from soybeans cooked for less than 30min was bluish, and that of Natto samples prepared from soybeans cooked for over 30min was reddish. The Natto samples prepared from soybeans cooked for 40 to 60min showed the minimum time to reach the maximum temperature in their fermentation, and they also showed the maximum cell number of Bacillus natto among the Natto samples prepared in this study. The activities of protease, γ-glutamyltranspeptidase and levansucrase, solubility of nitrogen, formol nitrogen contents, ammonium nitrogen contents and stringiness of viscous substance of Natto samples varied with the soybean cooking conditions. From the results of sensory evaluation of Natto samples, it was concluded that the optimum cooking time under this condition was 30-40min.

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The iron-binding activities of components in soy sauce were examined by using gel filtration chromatography. Soy sauce was separated into 5 fractions (P1-P5) by Sephadex G-25 column chromatography monitored by the absorbance at 275 and 400nm. Iron in soy sauce was mainly bound to high-molecular-weight components (P1 and P2). Simulated soy sauce consisting of sugars, amino acids, organic acids, and minerals was analyzed by the same column chromatography. Iron in the simulated soy sauce was eluted near P3. Irons bound to P1 and P2 were released by ascorbic acid and ethylene diamine tetraacetic acid, but they were little liberated by the treatment of trypsin, pronase, sodium dodecylsulfate, and 2-mercaptoethanol. About half amount of bound iron was released by the treatment of NaIO₄. The iron-binding components were considered to be mainly formed in the process of Koji preparation, heating of soy bean and aging of soy sauce.

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In this study, we measured the Ca content, hardness and pectin composition of brined ume fruit (Japanese apricot, Prunus mume Sieb. et Zucc. var. microcarpa Makino) containing egg shell ashed at various temperatures to clarify the effect of the egg shell on the hardness of the brined ume fruit. Furthermore, the tissue structure of the fruit was observed using a scanning electron microscope. The Ca amount in the egg shell increased when it was ashed from 700°C to 800°C. From an X-ray diffraction analysis, it is presumed that Ca in the dried egg shell (DES), ashed at 500°C (AES-500) and 600°C (AES-600) would exsist as CaCO₃, AES-700 and -750 might contain Ca as both CaCO₃ and CaO, and Ca in AES-800 and -900 might almost be only CaO. The hardness of the brined fruit was maintained by the addition of DES or AES. But the fruit with DES, AES-500 and AES-600 decreased in yield, which was expressed as the ratio of the brined fruit to fresh ume fruit used as raw material. The fruit with DES was similar to control in the ratio of 0.05N HCl soluble pectin (HSP) to total pectin, but was significantly lower in water soluble pectin (WSP), and higher in 0.4% hexametaphosphate soluble pectin (HXSP) and 0.05N NaOH soluble pectin (SSP). The fruit with AES-500 or -600 was almost the same as the fruit with DES in HSP, HXSP and SSP, and was similar to the fresh fruit in WSP. The fruit with AES-700--800 gradually decreased in WSP and HSP as the ashing temperature rose, but increased more and more in HXSP and SSP. From the scanning electron micrographs, firm rectangular cells were clearly observed in the sarcocarp of the fresh fruit, but cells of the brined fruit had transformed to unclear flat shapes. The cells of the fruit with DES, AES-500 or -600 were observed as crushed flat cells, but those of the fruit with AES-750 or -800 were similar to that of the fresh fruit.

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Crude protein content, and free and hydrolyzed amino acid compositions of whole root flour of sweetpotato cultivars that included lines lacking β-amylase were investigated in 1990 and 1991. A statistic varietal difference in crude protein content was detected; however, the order of the rank was largely different between the two years. The amino acid composition of whole root flour was similar among the cultivars and their profile was almost the same as in previous reports, although the aspartic acid content varied most greatly among the cultivars. The most predominant free amino acid was always asparagine in every cultivar, whereas the total free amino acid content largely varied among the cultivars. There was a large varietal difference in free asparagine content, which was quite altered between 1990 and 1991. However, the correlation coefficients between free asparagine content and hydrolyzed aspartic acid content in both years were above 0.9. Thus, most of the variabilities in aspartic acid contents among cultivars were the results of the variations in free asparagine content.

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It is known that the deterioration of rice cakes largely depends on the temperature of the environment after manufacture of the rice cakes. The reason for this is that the physical state of water in the rice cakes is changed by the application of heat, and the restoration properties of the rice cakes are eventually lost. This study was made to numerically express the degree of deterioration of rice cakes based on the relationship between the temperature and the conductivity of the rice cakes. Four types of rice cake samples with different degrees of deterioration were prepared by repeating a heat treatment of 60°C for one hour, using a rice cake immediately after manufacture, The conductivities of these rice cake samples were measured as they were frozen by decreasing the temperature from 0°C. Measurement of the conductivity of the rice cake samples confirmed that thetemperature at which the conductivity drops sharply, due to freezing of the water in the rice cake, is related to the degree of deterioration. The deterioration is caused by the movement of water in the rice cakes when the moisture content of the rice cakes is controlled within the range of 41.5 to 44.0% at manufacture. This temperature can be used as an index to indicate the degree of deterioration of rice cakes. This fact was supported by DSC and DTA analyses, and the data for the solubility of starch in hydrochloric acid. In addition, it has been judged from a taste test of rice cakes manufactured without using any additives that there is a quality limit to the rice cake samples which were prepared by multiple heat treatments (three times). The conductivity drop temperature of the above-mentioned sample was-6.0±0.5°C.

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An improved method for the synthesis of hesperidin glycosides was developed using both β-cyclodextrin (β-CD) and α-rhamnosidase treatments. The reaction, which contained 0.5% (8.2mM) hesperidin as an acceptor, 5% soluble starch as a donor and 2 units/ml of cyclodextrin glucanotransferase (CGTase) from an alkalophilic Bacillus species was incubated at 40°C and pH 10 for 16h, was used as the standard reaction. During the transglycosylation reaction, both β-CD and an alkaline pH were very effective for solubilizing hesperidin, and the amount of hesperidin glycosides formed by CGTase with 5% β-CD as a donor at pH 10 was about 50 times greater than the amount formed with soluble starch at pH 5. During the purification steps, α-rhamnosidase hydrolyzed the unreacted hesperidin into lower molecular weight and more hydrophobic compounds (hesperetin-7-glucoside), but it did not hydrolyze the hesperidin glycosides. Therefore, hesperidin glycosides were easily separated from the unreacted hesperidin using Sephadex LH-20. Various kinds of natural pigments were stabilized against ultraviolet radiation using the prepared hesperidin glycosides.

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The fermented milk produced with lactic acid bacteria is reported to possess anticarcinogenic or antimutagenic activities¹⁾²⁾. HOSODA et al. examined the antimutagenic effects of the milks cultured individually using 71 strains and 76 strains of lactic acid bacteria on the utagenicities of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and 3-amino-1-methyl-5H-pyrido (3, 4-b) indol (Trp P-2), respectively, and showed that each strain displayed its characteristic antimutagenic effect of the respective mutagens³⁾⁴⁾. Kefir is known as an aged fermented milk product. The longevity of the people in the Cocasass region is postulated to be in part due to the comsumption of the fermented milk. Kefir is produced by Kefir granule in which various species of lactic acid bacteria, yeasts, and some species of acetic acid bacteria coexist⁵⁾. This prompted us to speculate that the fermented milk produced by the mixture of various species of lactic acid bacteria and other species of microbe might contain a wider variety of physiological substances, compared to the milk cultured with a single strain of lactic acid bacteria. Based on this idea, we attempted to prepare the aged-fermented milk with mixtures of various lactic acid bacteria and a yeast, and examined the antimutagenic activities toward various mutagens.

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