Estimation of Soluble Protein Concentration of White Wines Using Coomassie Brilliant Blue G-250

¹ John I. Haas, Inc., P.O. Box 1441, Yakima, WA 98907
² Department of Food Science and Human Nutrition, Washington State University, Pullman, WA 99164
³ Department of Food Science and Human Nutrition, Irrigated Agriculture Research and Extension Center, Prosser, WA 99350.

The Coomassie brilliant blue G-250 assay was evaluated for its ability to estimate the soluble protein concentration in Gewürztraminer, White Riesling, and Chenin blanc wines. The reaction of the dye with wine proteins required more time (about 45 min) than was required for the protein standard bovine serum albumin. Phenols which were not bound to proteins did not affect the reaction of the dye with the protein since removal of phenols by PVPP adsorption or ultrafiltration (10000 MW cut-off) did not affect the course of the reaction. The delayed dye protein complex formation may have been due to phenols bound to wine proteins. The Coomassie assay provided a rapid method for determining soluble protein concentrations in white wines, provided the protein-dye incubation period was critically timed. A reaction time of 55 minutes at 21°C ± 1°C is recommended.

Key words: protein assay, phenols, PVPP, dye-binding assay, fining

Submitted on August 17, 1988