To clarify the processing properties of "Sendango", a traditional food from Tsushima Island, obtained from fermented sweet potato, and the factors that show the characteristic physical properties of "Rokubee", a Sendango processed product, we examined and compared the physicochemical and viscosity properties, and chain lengths of amylopectin in Sendango starch and its raw material, the sweet potato starch. The surface of Sendango starch granules was rough and with holes, confirming that the granules were degraded by fermentation. Amylose ratio in Sendango starch was high, suggesting that amylopectin was degraded. In addition, the properties of Sendango starch indicated that it hard to gelatinization and easy to retrogradation; starch gel was hard, elastic, and viscous. These properties were associated with specific degradation of the short (A and B1) chains in the outmost shell of the amylopectin chain-length.

　In this study, we aimed to investigate the properties of polyphenols in the husk of the "water chestnut", which is an aquatic plant, and effects on postprandial blood glucose levels in humans. We prepared a hot water extract of the husk of the Japanese water chestnut (Trapa japonica), and investigated the content of polyphenols in the extract and their stability against heat. The result showed that the total polyphenol content in the hot water extract of water chestnut was approximately 200mg/100mℓ, and the total content of polyphenols (eugeniin, 1,2,3,6-tetra-O-galloyl-β-d-glucopyranose (TGG) and trapain) exclusive to water chestnut was approximately 20mg/100mℓ. Eugeniin and TGG were observed to be stable against heat; however, trapain was sensitive to heat (80℃ or higher). Twenty-one healthy volunteers drank water or the hot water extract of water chestnut husk (200mℓ), and were subjected to a cooked rice load test. The group that consumed the hot water extract of water chestnut exhibited significant suppression in blood glucose elevation 20 and 30 minutes after meal. This was speculated to be due to the inhibitions of carbohydrase activity and glucose uptake into the small intestine by the polyphenols of water chestnut husk.

　We performed a detailed examination of how the quality of 'Kitanebari' varies depending on cultivation and storage conditions. The moisture content and viscosity were significantly lower and higher, respectively, in 'Kitanebari' than in Nagaimo. The differences in nitrogen levels in the fertilizer did not affect its moisture content and viscosity. As the nitrogen levels in the fertilizer increased, the polyphenol (PP) contents decreased. The polyphenol oxidase (PPO) activity showed an interaction between varieties and fertilizer nitrogen level. The PPO activity tended to be higher in 'Kitanebari' than in Nagaimo, and it increased with increasing fertilizer nitrogen levels. Nagaimo was more prone to browning when the fertilizer nitrogen levels increased. Excising the vine at an early stage tended to increase water content and decrease viscosity, suggesting that it became an immature rhizosphere. We demonstrated that early removal of vines significantly increased PPO activity and browning. However, harvest time did not affect moisture and viscosity. Changing the harvest time from fall to spring significantly increased PP content and PPO activity. In addition, when changing the harvest from fall to spring, Nagaimo became markedly brown. The storage period did not affect moisture and viscosity, but PP and PPO content significantly increased with storage. Thus, as the duration of storage increased, browning progressed. The degree of browning in 'Kitanebari' was slower than that in Nagaimo.

　During the Mizu-nasu eggplant pickling processing, there can be problems with the alum used to fix the eggplant's deep blue color. Primarily, browning can occur that alters the deep blue color of the eggplant. This study investigated the cause of pickle browning, and methods to improve pickle color. Minimal browning occurred on the side of the fruit closest to the stalk, or along the equator of fruit, which are areas where the anthocyanin levels are high. However, browning occurred more frequently at the fruit apex due to low anthocyanin levels after pickling. There was only 35% penetration of aluminum ion (Al^3＋) in the fruit peel in areas where browning occurred. Several methods were tested to improve the penetration of the color-fixing agent. Scraping the eggplant surface with rice hull before pickling increased penetration of the color-fixing agent into the fruit peel, thereby, suppressing browning. Thus, peel scraping with rice hull before pickling seems to be suitable for the suppression of browning and improving the color stability of Mizu-nasu eggplant pickles.