ナス果実の低温障害に関する研究 (第1報)

Abstract

This paper reports the effects of harvesting season and maturation of eggplant fruit on pitting injury and browing of seeds and pulp during low-temperature storage.Pitting injury was less frequent on unripe fruit (5-7 days old after flowering) and overripe fruit (24-27 days after flowering), and pitting injury was more frequent at the proper harvesting stage (14 days after flowering). On the other hand, the younger the fruit was, the more frequent the browning of seeds and pulp was during low-temperature storage. Pitting injury decreased during the late harvesting season, but the browning of seeds and pulp did not decrease. In contrast fruit stored at 20°C did not display pitting injury and the browning of seeds and pulp during storage at any season.The unripe fruit contained higher levels of polyphenols than fruit harvested at the proper stage or overripe fruit. Three days old fruit contained 344mg/100g f. wt of total phenols and the polyphenols content decreased with advance of the maturation of the fruit. For example, 13 days old fruit contained 55mg/100g f. wt of total phenols. The fruit at all stages contained a 30-40% o-diphenol fraction of total phenols. The main o-diphenol of eggplant fruit pulp was identified as chlorogenic acid by paper chromatography. As this polyphenol was fairly oxidised by the crude enzyme extracted from eggplant fruit pulp and its reaction mixture browned, it seemed to be the substrate of browning during storge.Total phenols content and o-diphenols content of unripe fruit rapidly increased before the browning of pulp and decreased as the browning of the pulp browned during low-temperature storage. On the other hand, total phenols content and o-diphenol content of overripe fruit which did not show the browning of pulp was almost constant during low-temperature storage. The activity of polyhenol oxidase increased rapidly before the browning of pulp and decreased after the browning of pulp during low-temperature storage, while the activity of polyphenol oxidase increased gradually in the unripe fruit stored at 20°C and the overripe fruit.