Effects of Must Polyphenoloxidase Activity and Timing of Sulfite Addition on the Color and Quality of Vitis rotundifolia and Euvitis Hybrid White Wines

¹ Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611
² Central Florida Research and Education Center, 5336 University Ave., Leesburg, FL 32748.

The effects of initial polyphenoloxidase activity (PPO) in the must and timing of the initial sulfite addition on the color of a white Euvitis hybrid wine and a white Vitis rotundifolia wine were evaluated. The non-sulfited Euvitis juice had high PPO and browned extensively if sulfite was not added at crush. However, delaying sulfite addition until after cold settling (before fermentation) or after fermentation reduced total phenolics and produced wines with better color as compared to addition of sulfite at crush, but did not significantly effect overall sensory quality. The same wine treatments with limited or no PPO activity in the must (inactivated by temporary low pH) generally browned to a greater extent than the same wines with full PPO activity. In contrast, the Vitis rotundifolia juice was very light due to a lack of indigenous PPO. Sulfite additions after cold settling or fermentation reduced total phenolics and were as effective as a sulfite addition at crush in preserving wine color. V. rotundifolia wine produced by delaying sulfite addition until after fermentation was significantly different in sensory quality (less astringent) than the sulfite-at-crush wine.

Key words: polyphenoloxidase, sulfites, white wines

Submitted on July 20, 1990