Stephan Sommer* and Federico Tondini
*California State University, Department of Viticulture and Enology, 2360 E. Barstow Ave. M/S VR89, Fresno, CA 93740 (ssommer@csufresno.edu)

Protein stability is an important quality attribute in wines, where haze in the bottled product will lead to consumer rejection. Traditionally, stability is achieved by bentonite addition; however, environmental concerns and disposal problems mean that alternatives are required to achieve the same goal. We evaluated Sacharomyces paradoxus, chitosan, polystyrene, carboxymethyl cellulose, and bentonite as such alternatives. Trials in finished wines were agitated for 10 hr overnight and analyzed for turbidity and color characteristics spectrophotometrically. Experiments were conducted with wines that were expected to develop protein instabilities: Muscat Canelli, White Zinfandel, Cabernet Sauvignon blanc de noir, Barbera rosé, and Touriga Nacional. Results indicate that S. paradoxus can help remove proteins from wine. Wines with low protein instability can be stabilized by S. paradoxus and by poly- styrene and chitosan to a lesser degree. All fining agents except bentonite showed variability in fining efficiency between white and red wines that can be explained by matrix interferences in red wine and the specific reaction mechanisms of the additive. With an average protein reduction ~50%, none of the alternative fining methods could reach the efficiency level of bentonite. Experiments in a model system confirm the findings and explain some of the mechanisms involved: for example, the specificity of chitosan and challenges related to the use of yeast as a fining agent. Carboxy methyl- cellulose and polystyrene show promise but need to be evaluated further to optimize the application procedure.

Funding Support: n/a