Differences in monophenolic content and composition of persimmon fruit slices from different regions under fresh and microwave drying

Abstract

The browning of moon persimmons during the drying process was primarily caused by the oxidation of phenolic compounds. Additionally, microwave drying led to uneven browning of the fruit slices. This study aimed to evaluate effect of microwave drying on the content of 19 monophenolic compounds in moon persimmon fruit slices from six different regions (A1, A2, B1, B2, C1 and C2). The analysis was conducted using ultra-performance liquid chromatography with high-resolution mass spectrometry. The findings indicated that the three primary monophenols with the highest concentrations in fresh moon persimmon fruit slices were gallic acid, phenylalanine and catechin; these concentrations ranged from 0.554 to 6.797 mg/100 g. The distribution of monophenol species was higher in the outer edge region of the fruit slices, with 14 monophenols detected in the C2 region. Microwave drying increased gallic acid content and decreased other monophenol content. Monophenolic compounds under microwave drying underwent autoxidation and also transformed into each other. The B2 region of the fruit slices displayed the earliest occurrence of browning and exhibited the most significant changes in both rate and magnitude of phenolic content. The colour deterioration of moon persimmon fruit slices during microwave drying is related to the change in phenol content, which may be caused by the phenol autoxidation reaction.