We investigated reaction conditions for leucrose production from sucrose by the crude dextransucrase from Leuconostoc mesenteroides. The optimum pH value and temperature of the reaction were approximately 5.0 and 30°C, respectively. The efficiency of conversion from sucrose to leucrose was remarkably increased by addition of fructose as an acceptor and the conversion rate from sucrose to leucrose was 75% when the concentration of fructose was nine times that of sucrose. The conversion rate was effectively increased in accordance with sucrose concentration. In order to obtain a high yield of leucrose the sucrose solution was continuously added to the mixture of the fructose and enzyme solution with keeping high ratio of fructose/sucrose. Thus, the maximum yield (26%) of leucrose from the total sugars including fructose was attained. Oligosaccharides which were presumed to be trisaccharides and higher molecules were also produced.

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Inhibition of respiration and fermentation of Debaryomyces hansenii, by aceti caid and the protection of liver extract were investigated by Warburg's manometric method. (1) At the lower concentration of 0.5%, acetic acid was assimilated by tested yeast as a respiratory substrate, however, 1% solution was entirely not assimilated. (2) When glucose, pyruvic acid, ethanol or a-ketoglutaric acid were used as a fermentable substrate, O₂ uptake and CO₂ production of tested yeast were inhibited at the higher concentration of 0.5% of acetic acid. However, when pyruvic acid was used as a fermentable substrate, CO₂ production was not inhibited even in 3% of acetic acid solution. (3) When pyruvi cacid, ethanol or a-ketoglutaricacid were used as a respiratory substrate, acetic acid inhibited remarkably O₂ uptakecompared to glucose substrate. From this results, it was estimated that acetic acid inhibited oxidative process following acetyl CoA. (4) In case of glucose used as a respiratory substrate, the addition of acidic fraction of liver extract stimulated O₂ uptake of the yeastcell. From this results, it was suggested that acidic substances in liver extract haveprotective effect for respiratory inhibition by acetic acid.

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Effects of heat treatment methods on soybean globulin gel viscosity were studied . Changes in viscosity during the heat treatment and thixotropic behavior of the s amples before and after the heat treatment were studied. β-Conglycinin became more viscous wh en a rising rate in temperature was small. On the other hand, the viscosities of glyc inin gels did not increase at all at any heating rate, except a case at 35°C/h. When the β-co nglycinin solutions were stood at 90°Cfor 20min during the heating process, their viscosity ies increased by this treatment and the final viscolities were also higher than those of the s amples treated by the standard method. In the case of glycinin, however, the response was more complex. The viscosities increased at low protein concentrations, whereas they sharply d opped after initial small increase in the cooling process at high protein concentrations. Th ese results suggest that the formed gels were destroyed by shear in the viscosity measuremen ts and the destroyed structures were not re-formed in the case of glycinin. It can therefore e be presumed that β-conglycinin gels were formed with non-covelent bonds which is easily res tored by standing. On the other hand, glycinin gel network, which seemed to be made up wi th disulfide bonds, may hardly be recovered by standing.

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Vinegar production was investigated using immobilized Acetobacter aceti cells entrapped in calcium alginate gel beads by fluidized bed type column reactors. The optimal immobilization conditions of acetic acid bacteria were as follows: a final concentration of sodium alginate, 1.0-1.5%; a concentration of calcium chloride, 2-3%; the diameter of calcium alginate gel beads, 1.1-1.5mm. In the continuous acetic acid fermentation using immobilized A. aceti cells, the maximum productivity of acetic acid, 7.2g/(l·h), was obtained at the dilution rate of 0.32h^-1. Furthermore, both the concentration of acetic acid produced and the productivity of acetic acid in this immobilized cell system were about twice as compared to those with free cells only. The continuous acetic acid fermentation with immobilized cells was carried out Using two reactors in series. The concentration of acetic acid produced using two reactors in series was higher than that using one reactor. It was concluded that the growing cells immobilized in calcium alginate were advantageous for vinegar production.

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Effects of various organic acids on thermal resistance of spores of Clostridium botulinum 62 A and 213 B, Clostridium sporogenes PA 3679 and Clostridium perfringens JCM 01382 were investigated. Thermal resistance of all the tested Clostridium spores was maximum at pH7.0 and it decreased with increasing acidity or alkality. In particular, it was remarkable in acidic side. The addition of 0.2-0.5% adipic acid at pH 5.5-9.0 decreased thermal resistance of spores with increasing concentration of adipic acid. Decreases of thermal resistance of C. botulinum and C. perfringens spores by addition of adipic acid were almost not affected by pH. However, that of C. sporogenes spores increased as pH droped. The addition of 0.2% of acetic, adipic, lactic, maric, citric, fumaric, gluconic, tartaric, succinic, sorbic or propionic acid at pH7.0 and 9.0 decreased thermal resistance of C. botulinum 62 A spore by 35-65%. At pH5.5, the decreasing actions of most of the tested organic acids on thermal resistance of C. botulinum 62 A spores were significantly reduced or disappeared, although those of adipic and acetic acid were powerful.

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Investigations have been carried out to determine the effect of cultivar, seed size, and crop year on the total and free sugar contents of soybeans of 13 cultivars grown at the same location in the normal and unseasonable of two crop years. When the seed size decreased, total sugar, free type of total sugar, raffinose, and stachyose contents increased (102-116%), and the increased ratios of raffinose and stachyose were higher than those of other sugars. On the other hand, only sucrose content slightly decreased (93-99%). The cultivar, as compared with the seed size, was more influencial on the all sugars, and higher contribution ratios were observed in cultivar. The unseasonable year showed high in all sugar contents (103-122%), and the highest difference between the two crop years was observed in the sucrose content. Significant differences were observed in total sugar, free type of total suger, sucrose, raffinose, and stachyose among the cultivars, and in total sugar, free type of total sugar, and sucrose between the crop years. From the contribution ratio, crop year was higher than cultivar in all sugars except raffinose and stachyose.

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Hesperidin solubility during the process of production and storage of clarified Satsumamandarin juice was investigated to produce clarified juice without formation of haze orsediment during storage. In turbid concentrated juice (raw material for clarified juice), sediment during storage. In turbid concentrated juice (raw material for clarified juice), soluble hesperidin, which comprised about 20% of total hesperidin immediately after extraction and concentration by evaporation, remained soluble during storage at-20°C, however, ; at higher storage temperatures its solubility rapidly decreased. In the clarification process of Satsuma mandarin juice by ultrafiltration (batch operation), the higher operating temperature gave a higher hesperidin content in the permeate. With respect to feeding juice concentration, the hesperidin content in the permeate from 20°Bx juice was slightly lower than that from 10°Bx juice, compared as a 10°Bx basis. Clarified Satsuma mandarin juice (50°Bx), in which excessive hesperidin was dissolved by filtration of heated juice, was storedat 37°C, room temperature, 5°C and-20°C for 3 months.
The higher the initial excessive hesperidin content in the clarified juice, the faster the rate of insolubilization of hesperidin at 37°C, room temperature and 5°C storage. However, excessive hesperidin remained soluble at-20°Cstorage. Hesperidin solubility in 50°Bx and 10°Bx clarified juice at room temperature was about 35 and 14-15mg/100g, respectively. These findings may be useful in determining whether clarified juice will develop haze orprecipitate during storage.

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Kinetic study on the gelation of fish meat sol was performed with an assumed reaction sequence to program the software for control of gel strength of kamaboko. Four different states, raw, gelation-possible, gelation-impossible and gelled state, were assumed for fish meat sol during the heating process of kamaboko. Raw state was changed into gelationpossible one, and then changed into gelation-impossible or gelled one. Parameters for the reactions were estimated to minimize the sum of the squares of the difference of computed value from corresponded data value. At higher temperature than 32.9°C, the rate of the reaction from gelation-possible state to gelation-impossible one was higher than that from raw to gelation-possible one. Simulations were tried with the estimated values, and the results could explain the relationship between heating condition and gel strength successfully.

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Since it is difficult to judge maturity of kiwifruit by appearance, growers measure the soluble solids (S.S.) content using a refractometer. In order to find a suitable harvest index other than S.S. and firmness, starch content, total pectin (TP) and water soluble pectin (WSP) contents, β-amylase and polygalacturonase (PG) activities of kiwifruit were investigated. The S.S. content, measured with a refractometer, and firmness of kiwifruit stored at room temperature (20°C), with or without ethylene treatment were compared. Kiwifruit treated with ethylene after harvest showed more uniform firmness and S.S. content than those without ethylene treatment. β-Amylase and PG activities, TP and WSP contents could not be used as alternative harvest and shipment indices for kiwifruit owing to fluctuation in their values. The use of S.S. content as a maturity index appeared to be applicable in 'Hayward' but not in the early-ripening cv. Koryoku. If 'Koryoku' were to be harvested based on the optimum S.S. content, the fruit would have to be shipped within 2 days after ethylene treatment to maintain suitable firmness. In 'Koryoku', the period of highest starch content is a better maturity index than S.S. content. Harvesting at the suitable period would ensure longer storage and maintenance of firmness and sweetness.

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Spraying with 5ml of 40% or 60% ethanol per 6l container advanced the ripening of Cavendish bananas stored at 20°C by 1-3 days. The more rapid rate of ripening in the treated fruits resulted in lower starch content and higher contents in total sugar, sucrose and reducing sugar compared with the control. α-Amylase activity was generally higher in fruits treated with 40% or 60% ethanol. The increase in the activity of the enzymes occurred much later than the commencement of starch hydrolysis.

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[in Japanese]

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