Formation of n-Hexanal from Rind Tissues as Related to Aging and Disorder of Rind of Naruto (Citrus medioglobosa hort. ex Tanaka)

Abstract

n-Hexanal was found in macerated rind tissues of Naruto (Citrus medioglobosa hort. ex Tanaka). Hexanal formation was thought to be catalyzed by enzyme system. In this reaction, optimum pH was about 4.5.
Rates of hexanal formation were closely associated with the degree of degreening of the fruit rind: their order was CEPA-treated fruits>outside fruits>inside or GA-treated fruits. There was a high rate of the hexanal formation in the fruit rind affected by ‘rind yellow spot’, a physiological rind disorder of Naruto, compared to healthy fruit rind. The hexanal formation was influenced by ambient temperature to which fruits had been exposed. A higher rate was observed on fruits held at 20°C than those held at 5°C. After transfer of fruits from 5°C to 20 °C, the rate increased within 3-4 hours.
Possible physiological importance of the hexanal formation was discussed in relation to aging of the rind and ‘rind yellow spot’ which occurs in accordance with aging of the rind.