Study on the Mechanism of Enzymatic Browning and Its Inhibitors during Lonicera caerulea Fruit Pulp Beating

In order to solve the enzymatic browning phenomenon in the pulping unit of Lonicera caerulea fruits and improve its utilization value. The main phenolic substrates involved in the enzymatic browning reaction in the pulping process of Lonicera caerulea fruits were investigated, and the interactions between phenolic substrates and epicatechin on the reaction of polyphenol oxidase (PPO) were analyzed and its mechanism of enzymatic browning was also determined. The three most effective inhibitors were further selected by comparing the effects of ascorbic acid, L-cysteine, calcium chloride, EDTA-2Na, and citric acid additions on the browning inhibition rate. The results showed that epicatechin was the primary influencing factor involved in enzymatic browning in the pulping process of Lonicera caerulea fruits, and the quenching mechanism of epicatechin on PPO was static quenching. The response surface optimization test determined the optimal combination of composite inhibitors as 0.11% ascorbic acid, 0.11% L-cysteine, and 0.08% EDTA-2Na, and the browning inhibition rate of Lonicera caerulea fruits juice under this condition was 93.17%. It indicates that the above composite inhibitors can inhibit the enzymatic browning in the pulping process of Lonicera caerulea fruits.