Characterization of polyphenol oxidase from Cape gooseberry (Physalis peruviana L.) fruit

Cape gooseberry (Physalis peruviana) is an exotic fruit highly valued, however it is a very rich source of polyphenol oxidase (PPO). In this study, Cape gooseberry PPO was isolated and biochemically characterized. The enzyme was extracted and purified using acetone and aqueous two-phase systems. The data indicated that PPO had the highest substrate affinity for chlorogenic acid, 4-methylcatechol and catechol. Chlorogenic acid was the most suitable substrate (K-m = 0.56 +/- 0.07 mM and V-max = 53.15 +/- 2.03 U-PPO mL(-1) min(-1)). The optimal pH values were 5.5 for catechol and 4-methylcatechol and 5.0 for chlorogenic acid. Optimal temperatures were 40 degrees C for catechol, 25 degrees C for 4-methylcatechol and 20 degrees C for chlorogenic acid. In inhibition tests, the most potent inhibitor was found to be ascorbic acid followed by L-cysteine and quercetin. This study shows possible treatments that can be implemented during the processing of Cape gooseberry fruits to prevent browning. (C) 2015 Elsevier Ltd. All rights reserved.