SPECTROSCOPIC AND KINETIC STUDIES OF PEAR POLYPHENOLOXIDASE INACTIVATION BY 4-HEXYLRESORCINOL

ABSTRACT 4-Hexylresorcinol (4-HR) has become increasingly used as an anti-browning agent. Due to its popularity, knowledge of its mechanism of action (MOA) is of great interest. 4-HR is known to affect browning reactions acting at different levels on different polyphenoloxidase (PPO) isoenzymes. Presented in the work is additional evidence of the inactivatory effects of 4-HR on pear PPO. 4-HR inactivates PPO in a pH dependent manner (pH values of around 4 being optimal for the inactivation reaction). This reaction strongly dependent on the 4-HR concentration is expected for a bimolecular reaction. Spectroscopic studies show significant differences between the interaction of 4-HR and ascorbic acid with PPO products. Ascorbic acid, not 4-HR, qualitatively modifies the absorption spectra of PPO products, pointing to a direct interaction of ascorbic acid. PRACTICAL APPLICATIONS Understanding the mechanism of action of browning inhibitors would allow optimal use in preventing fruit decay, especially that of fresh-cut fruits. The inactivatory effect of 4-HR on pear PPO favors simultaneous use with canonical PPO inhibitors because of their likely synergistic effects.