Change of the phisico-chemical indices and the oxidative enzymatic activities during the white grapes ripening

Abstract

The aim of this study was to follow up the evolution of both the physico-chemical indices and the
dynamics of the oxidative enzymes during the maturation of white grapes, more particularly until the
grapes reach technological maturity. Studying the dynamics of the physico-chemical indices during the
maturation of the grapes an increase of the content of glucides, polyphenols, antiocyanins,
simultaneously with the decrease of the acidity was noticed. The enzymatic activity of tyrosinase is high
at the moment when the grapes are in the beginning of the ripening period and afterwards it presents a
decline during the ripening of the grapes, having a relatively low level before harvesting. The enzymatic
activity of the laccase increases up till the full maturity of the grapes, then it decreses a little before the
harvesting of the fruit, having lower values than at the start of ripening. The enzymatic activity of the
peroxidase increases up till the full maturity of the grapes, then it decreses a little before the harvesting
of the fruit, having lower values than when it begins to ripen.