title: Elucidation of the mechanism of enzymatic browning inhibition by sodium chlorite.
abstract: Sodium chlorite (SC) is a well known anti-microbial agent and its strong inhibitory effect on enzymatic browning of fresh-cut produce has recently been identified. We investigated the effect of SC on polyphenol oxidase (PPO) and its substrate, chlorogenic acid (CA), as it relates to the mechanisms of browning inhibition by SC. Results indicate that the browning reaction of CA (1.0mM) catalyzed by PPO (33U/mL) was significantly inhibited by 1.0mM SC at pH 4.6. Two PPO isoforms were identified by native polyacrylamide gel electrophoresis, and both were inactivated by SC (3.0mM). This suggests that SC serves as a PPO inhibitor to prevent enzymatic browning. Furthermore, the effect of SC on the stability of CA in both acidic (pH 4.5) and basic conditions (pH 8.3) was studied by UV-Vis scan and LC-MS analysis. The results showed that at the presence of SC (3.0mM), CA (0.1mM) degraded to quinic acid and caffeic acid as well as other intermediates. Hence, the anti-browning property of SC can be attributed to the two modes of action: the inactivation of polyphenol oxidase directly and the oxidative degradation of phenolic substrates.
authors.affiliation: The Department of Food Science and Engineering, Sichuan University, Chengdu 610065, PR China; Produce Quality and Safety Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705, United States. Electronic address: heq361@163.com.
authors.forename: Qiang
authors.initials: Q
authors.lastname: He
authors.affiliation: Produce Quality and Safety Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705, United States. Electronic address: Yaguang.Luo@ars.usda.gov.
authors.forename: Yaguang
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Food Composition Laboratory, Beltsville Human Nutrition Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705, United States. Electronic address: Pei.Chen@ars.usda.gov.
authors.forename: Pei
authors.initials: P
authors.lastname: Chen
keywords: Anti-browning; Chlorogenic acid; Polyphenol oxidase; Sodium chlorite