Temperature Influence on Muscadine Wine Protein Characteristics

¹ Center for Viticultural Sciences, Florida Agricultural & Mechanical University, Tallahassee, FL 32307.

Muscadine wine proteins were characterized on the basis of their isoelectric points and molecular weights. Two-dimensional gel electrophoresis of the protein extracts from Carlos and Welder wines resulted in bands with molecular weights between 12 000 and 50 000 daltons, and their isoelectric points ranged from 4.6 to 8.8. A protein stability test in which the wines were stored at 49°C (120°F) for four days showed that some protein bands, especially those with molecular weights above 32 000 daltons, were unstable. Changes in protein configuration during fermentation are suggested by the fact that while the molecular weights of some protein bands in the wines were the same as those found in their juices, their isoelectric points differed. Similar observations were made when the wines were stored at 49°C. Browning of wines, which occurred when the wines were kept at this temperature, was effectively inhibited by potassium metabisulfite. Tiron and EDTA had no effect on the browning reaction, which suggests a non-homolytic reaction pathway, possibly a Maillard-type reaction.

Key words: Vitis rotundifolia, proteins, browning reaction, heat stability, wines

Submitted on January 29, 1987