Inhibitory effect of rice bran extract on polyphenol oxidase of potato and banana

Buffalo cheese whey hydrolyzed with Alcalase as an antibrowning agent in minimally processed apple

Buffalo whey was hydrolyzed with Alcalase for different times t_i (i = 0, 0.5, 1, 2, 3, 4 or 6 h) and the browning inhibition of minimally processed apples was investigated. The hydrolysis process was followed by determination of the degree of hydrolysis. In order to understand possible modes of action on the enzymatic browning, whey was submitted to the analysis of antioxidant activity (ABTS^·+ radical sequestration, Fe²⁺ chelating activity and reducing power), reactivity with quinones and inhibitory activity on polyphenol oxidases (PPO) extracted from Red Delicious apples. Buffalo whey showed significant increase in degree of hydrolysis, antioxidant activity, reactivity with quinones and PPO-inhibitory activity as a function of the hydrolysis time. Maximum PPO-inhibitory activity was observed from 4 h hydrolysis (t_4h hydrolysate), reaching about 50% inhibition. Then, slices of minimally processed apples were immersed in a buffered solution of the t_4h hydrolysate, packed and subjected to instrumental color evaluation during storage for up to 6 days. As for the ability to inhibit the browning of the minimally processed apples, the hydrolyzate kept the L∗ parameter of the apples during 6 days of storage, not statistically differing from the metabisulfite. In addition to the luminosity, the hydrolyzed whey was able to maintain the browning index of the apples at lower values during this storage time compared to the non-hydrolyzed whey. These results evidence possible applications of buffalo whey hydrolyzed with Alcalase as a natural substitute for additives conventionally used in the control of enzymatic browning in foods.