The enzimatic activity of peroxidase (POD) and polyphenoloxidase (PPO) extracted from three grape cultivars (Vitis vinifera L.), cultivated in Marialva city, state of Paraná, was evaluated in this study. The enzymatic extracts were prepared starting from the Rubi, Borbon and Benitaka grape cultivars pulp and peel. The activity of the peroxidase was 53.00 units/100 g in the extract from the Rubi cultivar peel, and 327.00 units/100 g from the Benitaka cultivar, these values being superior to those observed in the same cultivars pulp extracts, which were 7.67 units/100 g and 44.00 units/100 g respectively. However, the result was opposite in the Borbon cultivar, with values of 141.11 units/100 g in the pulp and 11.50 units/100 g in the peel being found. The results of the polyphenoloxidase in the Borbon cultivar activity were 100.18 units/100 g in the pulp and 102.60 units/100 g in the peel, and in the Rubi and Benitaka cultivars were 60.40 units/100 g, 48.62 units/100 g in the pulp and 17.40 units/100 g, and 26.20 units/100 g in the peel, respectively. Protein determination was carried out in each extract, and the results found in the pulp and peel, respectively, were 0.56 and 0.64 mg/100 g for cultivar Benitaka, 1.38 and 6.45 mg/100 g for cultivar Rubi, and 21.38 and 5.68 mg/100 g for Borbon. The extracts were submitted to thermal treatments (60°C, 65°C, 70°C and 75°C for a 1 to 10 minutes period) to observe the behavior of the peroxidase and polyphenoloxidase enzymatic activity, being verified a continuous decrease of the peroxidase and polyphenoloxidase activities as a result of the thermal treatment. The extracts of the Rubi and Benitaka cultivars were more heat stable than the extract from the Borbon cultivar for both enzymes. However, the temperatures used were not enough for a total inactivation of the enzymes.
peroxidase; polyphenoloxidase; activity; grape; Vitis vinifera
