CHANGES IN THE CONTENTS OF PHENOLIC SUBSTANCES, PHENYLALANINE AMMONIA-LYASE (PAL) AND TYROSINE AMMONIA-LYASE (TAL) ACCOMPANYING CHILLING-INJURY OF EGGPLANT FRUIT

The mechanism of browning, which is a typical chilling-injury of eggplant fruit (Solanum melongena L.), was investigated by determining the changes of phenolic substances, phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) either during storage at 1°C or after exposing fruit to low temperature for various periods. Chlorogenic acid and its isomer, the main substrates for browning, were isolated from eggplants by column and paper chromatography. Rf values and various color reactions of the above acids were compared with those of authentic chlorogenic acid. After 2 days of cold storage at 1°C, when browning was initiated, chlorogenic acid content decreased to less than half that of the initial day, rose to a maximum after 4 days, and then decreased rapidly. PAL activity increased to a peak after 2 days at 1°C, then decreased over 10 days as browning increased. TAL activity also increased after transfer from 1°C to 20°C. It is suggested that rapid turn-over of chlorogenic acid occurs in the early stage of cold storage of eggplant fruit, and development of browning is closely related to chlorogenic acid, PAL and TAL. © 1979.