Peach polyphenol oxidase inhibition by beta-cyclodextrin and 4-hexylresorcinol is substrate dependent.

摘要

Polyphenol oxidase (PPO; catechol oxidase) was extracted from whole peaches, and its catecholase activity was studied spectroscopically against 3 substrates: catechol (Cat), 4-methyl catechol (4MC) and chlorogenic acid (CA). Peach PPO specificity was: CA > 4MC approx. = Cat. 4-hexylresorcinol (4HR, 0.5mM) inhibited oxidation of Cat and CA by >=50%, at all substrate concn., but had no effect on the oxidation of 4MC, suggesting that laccase-like activity was present in the extract. beta-cyclodextrin ( beta-CD, 10mM) inhibited only CA oxidation; this effect was not abolished when free substrate concn. were calculated, suggesting a mechanism, additional to substrate complexation, in beta-CD action. Combination of 4HR and beta-CD had only a weak inhibitory effect on CA oxidation. In conclusion, beta-CD and especially 4HR could be used as browning inhibitors in peach products, and also as tools for studying different phenol oxidases. A combination of both compounds is not recommended for peaches.