Changes of Phenolic Substances in Seedless White and Green Raisins before and after Washing and Their Relationship with Enzymatic Browning

【Objective】 By analyzing the changes of phenolic compounds before and after cleaning green raisins and their relationship with enzymatic browning, this project aims to explore the mechanism of enzymatic browning in cleaned green raisins. 【Method】 Through detecting the content changes of monomer phenols before and after cleaning green raisins, the activity changes of these phenols and polyphenol oxidase reaction of raisins were analyzed, and the substrates involved in enzymatic reaction were determined. At the same time, the main phenols affecting the browning of raisins during cleaning were obtained by correlation analysis method. 【Result】 Phenolic substances with quality changes before and after cleaning of green raisins included quercetin, catechin, caffeic acid, kaempferol, P- coumaric acid, chlorogenic acid, ferulic acid, protocatechuic acid, vanillic acid, gentisic acid, sinapic acid, syringic acid and gallic acid. Among them, quercetin, chlorogenic acid, caffeic acid, P- coumaric acid, kaempferol and catechin were the main phenolic substances involved in enzymatic browning of raisins before and after cleaning. 【Conclusion】 Before and after cleaning green raisins, browning degree of raisins is significantly correlated with quercetin, caffeic acid, kaempferol and catechin contents. The research results provide theoretical basis for exploring browning mechanism of raisins cleaning.