The relationship between freezing conditions and storage conditions and quality change of grated Chinese yam (Dioscorea polystachya) during freezing and storage was examined. The results showed that when grated Chinese yam (Dioscorea polystachya) thawed right after freezing, there was no difference in viscosity, color difference value, and drip loss regardless of the freezing conditions (dry ice snow freezing, air blast freezing, or medical freezer freezing). On the other hand, for medical and air blast freezing, viscosity decreased after －15℃ storage for two months. For three months storage, viscosity decreased for all freezing conditions at －15 to －20℃. However, when the storage temperature was －30℃ or lower, there was no significant decrease in viscosity up to 4 months of storage. There was almost no difference between storage temperatures from －30℃ to －130℃. The increase in drip loss and color change as well as viscosity change were progressed at temperatures between －15℃ and －20℃, but were suppressed at temperatures lower than －30℃. These results suggest that the quality change of grated Chinese yam (Dioscorea polystachya) due to frozen storage tends to be more strongly affected by storage temperature than by freezing conditions.

　We investigated the effects of aerobic, anaerobic, and anaerobic-aerobic storage on the γ-aminobutyric acid (GABA), amino acid, organic acid, free sugar, and total polyphenol content, and eggplant fruit quality. These fruits were sealed in gas-barrier bags to initiate anaerobic respiration and stored at 25℃. GABA content increased after one day of anaerobic storage. This high GABA content was maintained until day five post-storage under aerobic conditions. Fruit placed under anaerobic conditions for one day contained 1.4-1.7 fold higher GABA content than that stored under aerobic conditions. We did not observe any differences in GABA content between anaerobic and anaerobic-aerobic storage. Amino acids and organic acids associated with GABA metabolism, including alanine, succinic acid, lactic acid, and acetic acid, increased under anaerobic conditions. In contrast, glutamic acid, glutamine, aspartic acid, malic acid, and citric acid contents decreased under the same conditions. The content of these components was found to be equivalent between the fruits continuously stored under aerobic conditions and those switched to aerobic conditions after one day of anaerobic storage. When the fruits were stored under anaerobic conditions for more than three days, their marketability was strongly decreased owing to color fading and off-flavor development. These results suggest that short term anaerobic treatment by respiration in a sealed package followed by aerobic storage is an effective method for increasing GABA without quality loss.

　We examined whether Chinese yam powder can be used as a stabilizing agent for ice cream. The findings of this study indicated that adding Chinese yam powder allows for controlling overruns of ice cream. Moreover, the consistency of an ice cream containing 0.5% Chinese yam powder was comparable to that of an ice cream containing 0.1% guar gum, suggesting that Chinese yam powder affects smoothening the texture of ice cream. Analyzing the optimum amount of Chinese yam powder to be added revealed that adding 0.5% yields the most sensually excellent results. Furthermore, the ice cream containing 0.5% Chinese yam powder was better at retaining its shape than an ice cream without any additives. The above results demonstrate that Chinese yam powder can be utilized as a stabilizing agent for ice cream.

　Streptococcus mutans is a major cause of dental caries. The water-soluble fraction of natto exhibits biofilm inhibitory effects against S. mutans. S. mutans is genetically and phenotypically diverse, and its biofilm-forming ability differs at the strain level. This study investigated the biofilm inhibitory effects of natto against nine S. mutans strains, with different genotypes and biofilm-forming abilities, isolated from the human oral cavity. We evaluated the biofilm inhibitory ability of natto produced on a laboratory scale. γ-Polyglutamic acid, the main component of stringiness in natto products, and the protease activity were identical between laboratory-produced natto and commercial products. The water-soluble fraction obtained from natto dose-dependently inhibited biofilm formation in all the tested S. mutans strains. Moreover, the biofilm inhibitory effect of commercially available subtilisin NAT, the major protease found in natto and also known as nattokinase, was similar to that of natto extract. These results suggest that natto has biofilm inhibitory effects against several S. mutans strains and can be used as a preventive food of dental caries.