Polyphenol oxidase (PPO) was extracted from whole peaches and its catecholase activity was studied spectrophotometrically against three substrates: catechol (Cat), 4-methyl catechol (4MC), and chlorogenic acid (CA). Peach PPO specificity...
morePolyphenol oxidase (PPO) was extracted from whole peaches and its catecholase activity was studied spectrophotometrically against three substrates: catechol (Cat), 4-methyl catechol (4MC), and chlorogenic acid (CA). Peach PPO specificity was: CA > 4MC ≈ Cat. 4-hexylresorcinol (4HR, 0.5 mM) inhibited oxidation of Cat and CA by 50% or more, at all substrate concentrations, but had no effect on the oxidation of 4MC, suggesting that laccase-like activity was present in the extract. β-cyclodextrin (β-CD, 10 mM) inhibited only CA oxidation and this effect was not abolished when free substrate concentrations were calculated suggesting a mechanism, additional to substrate complexation, in β-CD action. Combination of 4HR and β-CD had only a weak inhibitory effect on CA oxidation. In conclusion, β-CD and specially 4HR could be used as browning inhibitors in peach products and also as tools for studying different phenol oxidases. Combination of both compounds is not recommended for peaches.Se extrajo la enzima polifenoloxidasa (PPO) a partir de duraznos completos y se estudió su actividad catecolasa, espectrofotométricamente, frente a tres diferentes sustratos:catecol (Cat), 4-metilcatecol (4MC) y ácido clorogénico (CA). La especificidad de la PPO fue: CA > 4MC ≈ Cat. El 4-hexilresorcinol (4HR, 0,5 mM) inhibió, en un 50% o más, la oxidación de Cat y CA, pero no tuvo ningún efecto sobre la oxidación del 4MC, lo cual sugiere que el extracto posee actividad lacasa. La β-ciclodextrina (β-CD, 10 mM) inhibió únicamente la oxidación del CA, aún si se consideran las concentraciones libres del sustrato, lo cual sugiere que la acción de la β-CD depende de un mecanismo adicional a la complejación de sustrato. La combinación de ambos inhibidores tuvo un efecto débil sobre la oxidación del CA. Se concluye que la β-CD y especialmente el 4HR pueden ser usados como inhibidores del oscurecimiento enzimático en productos de durazno, así como para estudiar los diferentes tipos de fenoloxidasas. La combinación de ambos agentes no es recomendable en duraznos.