Tratamento térmico com vapor e adição de xantana para preservação de compostos bioativos fenólicos e da atividade antioxidante de polpas de mirtilo

Abstract

Blueberry is considered one of the richest fruits in antioxidants, whose activity is related to the presence of bioactive compounds. The pulp of this fruit has great importance, since it is used in the elaboration of several other products. The use of new technologies of heat application and use of stabilizers have contributed to the reduction of losses of bioactive compounds. The objective of this work was to evaluate the effects of heat treatment by direct addition of steam and addition of the xanthan stabilizer, before pulping, on the content of phenolic bioactive compounds and antioxidant activity (ABTS and DPPH method) in blueberry pulp. Blueberries (Vaccinium ashei Reade) of the cultivar Powderblue were used and the fruits, added with 0.08% of citric acid, were thermally processed to 90 ° C by direct application of steam in an analogue vertical autoclave, with and without addition of 0.1% and 0.5% xanthan, and by direct heating in an open pan, with addition of 0.5% xanthan. The four pulps were evaluated for up to 90 days of storage under freezing, for the technological characteristics of total acidity, pH, total soluble solids, color and concentration of the bioactive compounds (total phenols and flavonoids, monomeric anthocyanins, hydrolyzable and condensed tannins, Anthocyanins) and antioxidant activity (ABTS and DPPH methods). The activity of the polyphenoloxidase enzyme in fruits and blueberry pulp at the initial timewas evaluated. The heat treatment performed on the pulps deactivated the polyphenoloxidase enzyme. High concentrations of phenolic compounds and total flavonoids, monomeric anthocyanins, condensed tannins, individual flavonoids, individual phenolic acids and antioxidant activity by the two methods of evaluation were verified throughout the storage in the pulps heat treated by direct addition of steam. To the heat treatment in open pan. The association with xanthan, especially when in a higher concentration, resulted in higher levels of monomeric and individual anthocyanins, hydrolyzable tannins, gallic and chlorogenic acids and quercetin in pulps at all storage times. The phenolic bioactive compounds had positive correlation for the two methods of antioxidant activity (ABTS and DPPH), except the hydrolysable tannins that had only for the ABTS method.