Effect of peroxidase (POD) and polyphenoloxidase enzymes (PPO) on Benitaka and Rubi grape cultivars and on products processed in the form of juice and jelly

Peroxidase (POD) and polyphenoloxidase (PPO) are oxidative enzymes related to the darkening process suffered by fruits. Thus, the control of the effects of these enzymes, in the preservation of fruit, in order to minimize the darkening process is considered of great importance for food processing technology. The present study investigated the effects of POD and PPO on fresh grapes from Benitaka and Rubi cultivars, as well as the thermal stability and the residual enzymatic activities in the processing of juice and jelly (extra and light). Moreover, the microbiological quality of the processed products was evaluated. It was observed that, the effect of the POD enzyme, from the soluble fraction, as well as from the ionically bound fraction, was similar in both varieties of grapes, Benitaka and Rubi. But the effect of the PPO enzyme was higher in the Rubi variety. Operations such as cooking and pasteurizing were the most efficient processes to reduce the residual enzymatic effect of POD and PPO in grape jelly, in comparison to the juice. Although such processes were not enough for total enzymatic inactivation, they permitted a considerable reduction, thus were efficient to guarantee the microbiological safety of the products, such as jelly and juice.A peroxidase e a polifenoloxidase estão relacionadas com o escurecimento de frutas, por isso o controle das atividades destas enzimas é de grande importância para a tecnologia de alimentos. Neste trabalho estudaram-se as atividades dessas enzimas nas uvas frescas das cultivares Benitaka e Rubi, bem como as suas termoestabilidades e as suas atividades enzimáticas residuais no suco e nas geléias (extra e light). Foi também avaliada a qualidade microbiológica dos produtos elaborados. As atividades da enzima POD, tanto da fração solúvel quanto da ionicamente ligada, foram semelhantes nas uvas das duas variedades, Benitaka e Rubi. A atividade da enzima polifenoloxidase foi maior na variedade Rubi. As operações de cocção e pasteurização foram mais eficientes para baixar as atividades enzimáticas residuais da POD e PPO quando aplicadas às geléias de uva, em comparação com o suco. Embora não foram suficientes para a total inativação enzimática, essas operações reduziram-nas consideravelmente, e foram eficientes para garantir seguridade microbiológica dos produtos, geléias e suco.172177Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES