Ethyl 3-mercaptopropionate, a safe food flavoring, competitively inhibits polyphenol oxidase and prevents browning in fresh-cut produce

Enzymatic browning, caused by polyphenol oxidase (PPO), degrades fresh-cut produce, resulting in significant economic losses. This study investigates ethyl 3-mercaptopropionate (EMP), a safe food flavoring, as a novel PPO inhibitor. EMP at 50-100 μL/L effectively prevented browning in both fresh-cut potatoes and tobacco leaf pulp, performing comparably to the standard inhibitor sodium bisulfite but offering better safety. Purified potato PPO showed nanomolar sensitivity to EMP with an IC₅₀ of 156.7 ± 17.26 nM. Molecular modeling and dynamics simulations revealed that EMP acts as a competitive inhibitor, competing with the natural substrate for the PPO active site. By binding key active site residues, including copper-coordinating histidines, EMP induces a more rigid enzyme structure, hindering its catalytic activity. These findings establish EMP as a potent competitive inhibitor, presenting a promising, safe, and effective strategy to control enzymatic browning in fresh-cut produce. This research also provides valuable mechanistic insights for developing improved anti-browning methods.