Regulatory Effect of Sulfur Dioxide on the Synthesis of Phenolic Substances and Antioxidant Capacity of Postharvest Grape Peel
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Abstract:
In order to explore the effect of sulfur dioxide (SO2) on the synthesis of phenolic compounds and antioxidant capacity of grape peel, this research used Munage grape as the test material, which was fumigated with 500 μL/L SO2 for 2 h then stored at (0±1) ℃ for 44 d. The grape subjected to air fumigation was used as the control. The changes in the contents of phenolic substances were determined regularly, and the content of flavanol monomers was determined by HPLC. The results show that at the end of storage, the contents of total phenols, total flavanols, total flavones, total anthocyanins, (+)-catechin, (-)-epicatechin, (-)-epicatechin and (-)-epicatechin gallate in the SO2-treated group were 0.74, 1.26, 1.33, 1.33, 1.47, 1.79, 1.59 and 1.49 times those of the CK group, respectively. The DPPH radical scavenging activity, ABTS+ radical scavenging activity and FRAP were higher than the CK group by 13.76%, 20.44% and 4.98% respectively. The SO2 treatment induced to certain extents the expression of L-phenylalanine ammonia-lyase (PAL), Cinnamate 4-hydroxylase (C4H), 4-coumarate: CoA ligase (4CL), Chalconesynthase (CHS), Chalcone isomerase (CHI), Dihydroflavonol 4-reductase (DFR), Leucoanthocyantin reductase (LAR), Anthocyanidin reductase (ANR) genes. It was found that the SO2 treatment couldup-regulate the expression of phenolic synthesis-related genes, delay the decline in the contents of phenolic compounds, and improve the antioxidant activity of grape peel. This study provided a theoretical basis for studying the regulatory effect of SO2 on the synthesis of phenolic substances in postharvest grape.
