Catecholase Activity in Australian White Grape Varieties

Abstract

Catecholase activity, total phenolic content, initial optical density, and the browning capacity of grape juice from 14 white Vitis vinifera grape varieties were measured. Influence of site on these factors was studied for four of the varieties. Varietal differences, as well as some regional differences, were found for all measured variables. Catecholase activity was highest in Semillon and Traminer, and lowest in Rhine Riesling and Rkaziteli. Crouchen and Traminer were the most susceptible varieties to browning, while Sauvignon blanc was least susceptible. Although catecholase activity appeared to be an important factor in browning of juices, both the initial optical density, and, to a lesser extent, total phenolic content, also exerted some influence. A high proportion (63%) of the variability in browning by the juices examined could be explained by the interaction between catecholase activity, total phenol content, and initial absorbance of juices. Influence of clonal selection on browning is briefly discussed, as well as possible implications for the Australian white wine industry.