Yeast flora of three kinds of Georgian kefir grains was investigated. They were freeze-dried grains (FDG), water-soaked grains (WSG), and daily transferred active grains (DTG). Strains of three well-known yeast species, Saccharomyces unisporous, Candida kefyr, and Candida holmii were isolated from DTG. Only Saccharomyces unisporus strains were isolated from FDG and WSG. Furthermore, strains of Candida valida were contaminated at a ratio of 1 : 3 in WSG. These results would indicate that C. kefyr and C. holmii are less tolerant to freeze-drying compared with S. unisporus. Freeze-drying seems to damage the cells of C. kefyr and C. holmii by cold shock and a concentration of lactic acid produced by lactic acid bacteria in the kefir production. C. holmii is nutritionally exacting and grows slowly. The role of this species has not been clear, but some effects will be expected for stimulation of other microorganisms. Preservation of the kefir grain was discussed from the viewpoint of yeast flora.

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This study was planned to clarify the influence of dietary fibers as food additives on in vivo antibody production in mice with or without antigen stimuli. The results showed that in mice sensitized with TNP-KLH, serum antibody titer and IgG concentrations of the gellan gum-fed and κ-carrageenan-fed groups increased significantly compared with those of the cellulose-κfed group (control). Low molecular fraction obtained from cecal contents of the gellan gum and κ-carrageenan groups enhanced significantly proliferation activity of splenocyte in vitro as compared with those of the control group. The increase of the serum IgG concentrations in gellan gum and κ-carrageenan groups was also observed under the condition without sensitization. The splenocyte proliferation activity was also increased by low molecular fraction obtained from cecal contents of the gellan gum and κ-carrageenan groups. These results suggest that some kinds of dietary fibers administered orally are associated with an increase of humoral immune responses in mice and some parts of the increased responses may be introduced by low molecular fraction of cecal contents.

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Because light irradiation suppresses changes of chlorophyll, ascorbic acid, free amino acid and reducing sugar in postharvest komatsuna leaves, effect of light quality on changes of these components was studied. Red light suppressed most effectively, as white light, the changes of these components. Blue and green light somewhat suppressed, but farred light had no effect to suppress these components changes. When komatsuna leaf discs were floated on 2×10^-5 M 3- (3, 4-dichlorophenyl) -1, 1-dimethylurea (DCMU) solution in white light (2klx), reducing sugar content remarkably decreased in order to inhibit sugar biosynthesis by photosynthesis. Still, under the condition komatsuna leaf discs maintained chlorophyll content the same as water control in light. When red farred photoreversibility was examined by brief irradiation of low light intensity every 3 hours, chlorophyll content had obvious photoreversibility. But, ascorbic acid content had weak photoreversibility only and the maintenance rate was low under this condition, its content strongly depended on light intensity and duration of irradiation. These results suggest that phytochrome system functions in the maintenance of chlorophyll content and ascorbic acid content is affected by high energy reaction like a photosynthesis than phytochrome system.

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The stability and degradation pathways of barbaloin (BA) in aqueous solution were investigated over the pH range of 1.1-8.4. The experiments were performed at three different temperatures (5, 20 and 50°C) by the use of high performance liquid chromatography. The degradation of BA was observed as a pseudo first-order kinetics and shown to proceed via racemization (Keq) and degradation processes (K2), (Keq>K2). The racemization product, isobarbaloin (isoBA), further underwent the same degradation as did BA. 10-hydroxyaloins A (10-HA), 10-hydroxyaloins B (10-HB) and aloe-emodin (AE) were detected as the degradation products of BA and isoBA. On the basis of kinetic studies, it was found that the degradation rate of BA decreased with decreasing pH and temperature. The half-lives of BA at pH7.2 (20°C) and pH3.4 (20°C) were 1.15day and 5.00day, respectively. The present results are useful for the integrity of foods containing aloe.

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When chlorophyll a solution in 80% ethanol was incubated with various radical scavengers and antioxidants under the light (30 μmole·m^-2·s^-1), ascorbate and erythorbate inhibited effectively chlorophyll degradation. Boiled chloroplast suspension also retained green with addition of ascorbate under the light. Blanched florets held under the light showed no bleaching at the buds part, but showed complete bleaching at the stems part during 1 day of storage. The bleaching of stems under the light was slightly inhibited by the addition of exogenous ascorbate due to insufficient ascorbate absorption by the tissue and oxidation from ascorbate to dehydroascorbate in a day. Vacuum packaging with a gas barrier film retained green color in blanched floret held under the light.

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Respiration rate, glutamine/glutamic acid levels and the activities of glutamine synthetase (GS, EC 6.3.1.2) and glutamate dehydrogenase (GDH, EC 1.4.1.2) in the top and bottom portions of harvested asparagus spears (Asparagus officinalis L. cv. Welcome) were examined. Spears were stored for up to 5 days at 25°C. Respiration rate (CO₂ production) of the spears declined during the first 2 days of storage and increased subsequently until the end of the storage period. The respiration rate of the top portion was over 2 or 3 times greater than that of the bottom portion or intact spears. GS activity increased in the top and bottom portions of the spears after 1 day and declined to about 38% and 65% of the initial levels by day 5, respectively. GDH activities in the top portion as well as the bottom portion showed an increasing trend until the end of the storage. Glutamine level increased, whereas glutamic acid decreased in concentration substantially during the first 24 h after harvest, in the top and bottom portions of the spears. There was a highly significant negative correlation observed between GS activity and the glutamine and glutamic acid content in the top and bottom portions of the spears. On the other hand, a highly significant positive correlation between GDH activity and the glutamine and glutamic acid content in the top and bottom portions of the spears was observed.

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Tissue samples from cold-stored (0°C) 'Danshaku' potato tuber which underwent low temperature sweetening (LTS) were analyzed by differential scanning calorimetry (DSC) using a heating rate of 5°C /min. Results showed that LTS significantly lowered the onset temperature of melting. Tubers stored at 10°C did not sweeten and showed insignificant reduction of onset temperature. Total sugar levels were significantly related to T_p, T_o and T_e while off was significantly related to moisture content of the sample. The primary endotherm (average T_o=-3. 86°C) representing extracellular melting of water was observed for tubers stored at 10°C and 0°C ; a secondary endotherm representing freezing of intracellular water was observed in 41.18% of tissue samples from tubers stored at 10°C (average T_o=-3.22°C). Only 11.11% of tissue samples from tubers stored at 0°C showed a secondary endotherm (average T_o=-12.20°C), implying that high sugar levels reduced lethal intracellular freezing in cellular compartments. Hence, sugar accumulation induced by cold conditions may be a mechanism to delay freezing and reduce its harmful effects on cell compartmentation and function.

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