Inhibitory effects of organic acids on polyphenol oxidase: From model systems to food systems

Abstract

Organic acids are widely utilized in the food industry for inhibiting the activity of polyphenol oxidase (PPO) and enzymatic browning. This review discusses the mechanisms of inhibition of PPO and enzymatic browning by various organic acids based on studies in model systems, critically evaluates the relevance of such studies to real food systems and assesses the implication of the synergistic inhibitory effects of organic acids with other physicochemical processing techniques on product quality and safety. Organic acids inhibit the activity of PPO and enzymatic browning via different mechanisms and therefore the suitability of a particular organic acid depends on the structure and the catalytic properties of PPO and the physicochemical properties of the food matrix. Studies in model systems provide an invaluable insight into the inhibitory mechanisms of various organics acids. However, the difference in the effectiveness of PPO inhibitors between model systems and food systems and the lack of correlation between the degree of PPO inhibition based on in vitro assays and enzymatic browning imply that the effectiveness of organic acids can be accurately evaluated only via direct assessment of browning inhibition in a particular food system. Combination of organic acids with physical processing techniques is one of the most viable approaches for PPO inhibition since the observed synergistic effect helps to reduce the undesirable organoleptic quality changes from the use of excessive concentration of organic acids or intense physical processing.

Keywords:

• Organic acids
• polyphenol oxidase
• inhibition mechanism
• catalytic activity
• enzymatic browning
• model systems
• food systems

Conflict of interests

The authors declare no conflict of interest.

Additional information

Funding

This study was supported by the China Postdoctoral Science Foundation (2019M652288), National Natural Science Foundation of China (31860452) and Jiangxi Province Science Foundation for Youths (20181BAB214019).