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 (1.0 mM) catalyzed by PPO (33 U/
mL) was significantly inhibited by 1.0 mM SC at pH 4.6. Two PPO isoforms were identified by native polyacrylamide
gel electrophoresis, and both were inactivated by SC (3.0 mM). 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 (3.0 mM), CA (0.1 mM) 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.
Sodium chlorite (SC) is a well known anti-microbial agent and its strong inhibitory effect on enzymaticbrowning of fresh-cut produce has recently been identified. We investigated the effect of SC on polyphenoloxidase (PPO) and its substrate, chlorogenic acid (CA), as it relates to the mechanisms of browninginhibition by SC. Results indicate that the browning reaction of CA (1.0 mM) catalyzed by PPO (33 U/mL) was significantly inhibited by 1.0 mM SC at pH 4.6. Two PPO isoforms were identified by native polyacrylamidegel electrophoresis, and both were inactivated by SC (3.0 mM). This suggests that SC serves asa PPO inhibitor to prevent enzymatic browning. Furthermore, the effect of SC on the stability of CA inboth 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 (3.0 mM), CA (0.1 mM) degraded to quinic acid and caffeicacid as well as other intermediates. Hence, the anti-browning property of SC can be attributed to the twomodes of action: the inactivation of polyphenol oxidase directly and the oxidative degradation of phenolicsubstrates.
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