Nobuyuki Kozukue

Changes in the contents of phenolic substances, phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) accompanying chilling-injury of eggplant fruit

Abstract 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. R f 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.

Studies on keeping-quality of vegetables and fruits. III. Changes in sugar and organic acid contents accompanying the chilling-injury of eggplant fruits

Abstract The mechanism of chiiling-injury in fruits of eggplants (Solanum melongena L. cultivar ‘Hyonaga’) was investigated by determining the sugar and organic acid content during cold storage and after exposure to low temperature for various periods. Fructose, glucose and maltose were detected, and totalled more than 96% of total sugar on the initial day. Total sugar content increased to 30% higher than the initial day after 2 days of cold storage, and after that decreased gradually, while in 20° C-stored fruits it decreased sharply. Fructose, glucose and maltose increased rapidly after transfer from 1° C to 20° C. Succinic, oxalic, malic and citric acid were detected before storage. Malic and citric acid were found to be the main organic acids. The ratio of malic/citric acid in fruits stored at 1°C decreased during storage, while after storage at 20°C it increased. The ratio in fruits after transfer from 1°C to 20°C increased rapidly during the time course. The ratio of malic/citric acid ranged from 6.0 to 6.8 in healthy fruits, while it was below 5.9 or above 7.3 in chilled fruits. It is suggested that according to this ratio the degree of chilling-injury of eggplant fruits might be foreseen.

Determination of indole-3-acetic acid and abscisic acid in Japanese chestnuts by column chromatography on sephadex G-10 and reversed-phase high-performance liquid chromatography

Abstract A method for the separation and quantification of indole-3-acetic acid and abscisic acid in Japanese chestnuts has been developed by use of Sephadex G-10 column chromatography and a reversed-phase high-performance liquid chromatography (HPLC). For the first purification step, the plant hormones are extracted with methanol—water (80:20) then eluted as individual hormone fractions from a Sephadex column. The final purification was performed on a reverse phase (LiChrosorb RP-18, 5 μm), eluted with a linear gradient of 10–50% acetonitrile in 1% glacial acetic acid. The column effluent is monitored at 254 nm. This technique has been used effectively to analyze plant hormones in biological samples.