Catecholase Activity in Grape Juice and Its Implications in Winemaking

Abstract

Catecholase (polyphenoloxidase) activity was measured in grape juice as related to parameters and variables of direct interest to the wine industry, including grape ripeness, degree of pressing, and the effect of bruising. Berries of sixteen grape varieties were separated according to sugar content, and the resulting musts were assayed for enzymatic activity. Enzymatic activity in the juice was maximum before the grapes reached full maturity, and increased with pressure in pressing. Bruising of grapes under controlled conditions prior to juice separation greatly increased catecholase activity in the musts, but the increase was prevented when bruising was in the absence of oxygen.