Browning type in Chinese olive juice concentrate processing

Browning type in different stage and its mechanism were studied by detecting the polyphenoloxidase(PPO) activity,the content of polyphenol,the content of vitamin C,the content of 5-hydroxymethyl furfural(5-HMF),browning degree in each production process of Chinese olive juice concentrate.It was found that browning was mainly non-enzymatic in the processing with enzymatic browning inhibited by blanching.Oxidation and browning of vitamin C constantly existed with more than 90% loss in the processing and there was Maillard reaction in blanching,hydrolysis and concentrating process with the content of 5-HMF increasing to 0.9174 mg·L-1 in the end.