A yeast Saccharomyces cerevisiae is one of the most important microorganisms for human beings, because this yeast is necessary to produce almost all the fermented foods and alcohol beverages. During industrial processes using S. cerevisiae, numerous environmental stresses, such as supraoptimal temperatures, oxidation, hyperosmolarity, drying and freezing/thawing, are exposed to yeast cells. To improve the industrial fermentation processes, yeast cells should have higher levels of the tolerance against the environmental stress. In this review, we describe 1) the importance of the tolerance against the environmental stress of yeast cells during industrial uses, 2) molecular mechanisms of the tolerance against the environmental stress, and 3) molecular breeding of stress tolerant yeast strains.

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The mechanical and mastication properties of takuan (pickled radish) which is difficult to eat by the elderly, were examined for textural properties by mechanical and electromyography (EMG) techniques. Three kinds of takuans with different skin processing, such as one without any processing, one having small cuts on the skin and one whose skin being removed, were used for the test. The takuan with small cuts showed the minimum breaking load in a mechanical test. The EMG tests showed significantly higher number of chewing strokes and chewing time in the elderly subjects compared to the younger ones. However, chewing cycle, EMG amplitude and muscle activity per chew showed opposite trend. Among the above-mentioned processed takuans, samples without skin indicated the lowest burden on chewing because EMG parameters such as the chewing strokes, chewing time, EMG duration and muscle activity per chew showed the significantly small value. The results further suggested that the data of muscle potential amplitude showed a significant difference only in the elderly and the influence of the skin processing was different between the elderly and the young and that the effect of skin processing was significant only in the elderly.

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Excitation-Emission matrix (EEM) fluorescence spectroscopy was applied to estimate the mixture rate of the buckwheat flour and the wheat flour. Eleven kinds of mixture of the buckwheat flour and the wheat flour were measured by EEM with excitation wavelength range of 200-900nm and emission wavelength range of 200-900nm. PLS regression analysis was applied to the EEM data obtained from the above measurement and the prediction formula was calculated using seven latent vectors. Coefficient of the prediction formula showed that significant EEM data was contained in the excitation wavelength range of 340-555nm and emission wavelength range of 500-755nm. PLS regression analysis was again applied to the EEM data of the above limited wavelength area. The accuracy of the standard curve did not change significantly from the result when the range of the wavelength was not limited. Measurement time was reduced from 515 seconds to 105 seconds per each sample. EEM measurement is an applicable method to detect the mixture rate of buckwheat and wheat flours easily and rapidly.

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A simple and objective method to measure the bubble structure of bread was developed by using an image scanner and a digital image processing. A bubble-emphasized image was obtained as a result of scanning the sample in four orthogonal directions and min-combining to get the numerical value of the image of the lowest luminance in order to facilitate the detection of the bubbles from the cross-sectional images of a bread sample. Next, Otsu's thresholding method was applied to each blocked area of the images, and the bubbles were equally detected in the whole image. The most appropriate block size was 20×20 pixel on this occasion. Furthermore, after labeling the bubble parts of two kinds of commercial samples, average bubble size, average perimeter, number of bubbles in a unit area and porosity (ratio of bubble area to whole area) were calculated. All the parameters were significant (p<0.01) among the two commercially-available samples (t-test), which means the character of the bubble structures of the two samples were extracted successfully. The algorithm developed in this study for measuring bubble structure of bread allows to collect data easily, and does not need trial and error for the optimization of parameters regarding filters.

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Turbidity in dashi (soup-stock) made from some different kinds of the fushi (boiled, smoke-dried fish fillet) poses serious problems for the fushi shavings industry, because turbidity in dashi reduces the commercial value of the shavings of fushi to make clear soup, which is essential in Japanese dishes that usually required transparency. This study aimed to elucidate the relationship between the dashi turbidity and the chemical components of the dashi and the fushi. We also sought to determine the component mainly responsible for the turbidity. It was clear that the more crude fat the fushi contained, the more turbid the dashi became. The correlation coefficients (r=0.886) between the turbidity and the crude fat content of dashi indicated that the lipid were the main causative component of the turbidity. Observing the shaving with scattering electron microscopy, lipids of the fushi were found as granular fat globules between the dried muscular fibers in the fushi. These globules dispersed into the dashi during extraction. We also determined that the main lipid component in the dashi turbidity were triglycerides and phospholipids.

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Cubed infant milk was analyzed by ESR. The shape of milk is cube and easily soluble in hot water. This cubed milk was compared with infant cubed/powdered milk, nonfat dry milk, powdered milk for coffee and dried whole egg. In ESR spectrum in each specimen, a singlet at g=2.0 due to organic free radicals was observed. In some specimens, hyperfine signals of Mn²⁺ and a singlet at g=4.0 from Fe³⁺ were also detected. The intensity of the ESR signal of the each specimen increased linearly with microwave intensity, became saturated and reached at the threshold amount at the 10mW or 20mW range. After showing the threshold amount, the signal intensity decreased. The ESR signal intensity of infant milk was larger than that of other powdered milk ; powdered milk for coffee and nonfat dry milk. Regarding electron spin-lattice relaxation times T₁ and spin-spinrelaxation time T₂ of infant milk were 10μs and 60ns respectively. We concluded that the radicals analyzed in infant milk were the same radical species both in cubed milk and powdered milk.

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In this study, we examined the preventing effect of D-psicose on the accumulation of body fat in rats. Four-week-old Wistar rats were fed with a high fructose corn syrup(HFCS) diet or a HFCS diet containing 1.3%, 2.6%, 3.9% or 5.2% of D-psicose for 5 weeks. The effects of D-psicose on body weight, food intake, total fat and various blood biochemical parameters were examined. Rats fed with HFCS diet containing 5.2% of D-psicose showed a significant reduction in body weight compared to those fed with HFCS diet. The groups given D-psicose showed dose-dependent decrease in perirenal fat and total fat weight. These results suggest that D-psicose has an effect to prevent the accumulation of body fat against HFCS intake.

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In this study, we described the effects of pressure on the formation of OVA gels, and clarified the condition of denaturation of OVA and the lowest protein concentration needed to form gels of OVA with pressure treatment. The lowest protein concentration needed to form pressure-induced OVA gels was 7∼9%, and was about twice as high as the lowest protein concentration needed to form gels by heat treatment. Cohesiveness of the pressure-induced gels was higher than that of the heat-induced gels. The appearance and the hardness of the pressure-induced OVA gels depended on the difference of pressure. The pressure-induced OVA gel formed at 686MPa for 20min was transparent, but the gel formed at 510MPa for 2h was turbid and was clearly harder than the gel formed at 686MPa.

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[in Japanese]

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