Sustainable Replacement Strategies for Bentonite in Wine Using Alternative Protein Fining Agents

Protein stability is an important quality attribute in wines and protein haze 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. In this study, the use of Sacharomyces paradoxus, chitosan, polystyrene, carboxymethyl cellulose, and bentonite were evaluated. Trials in finished wines were agitated for 10 h overnight and analyzed for turbidity and color characteristics spectrophotometrically. Experiments were conducted with wines that are expected to develop protein instabilities, Muscat Canelli, White Zinfandel, Cabernet Sauvignon blanc de noir, Barbera rose, and Touriga Nacional. Results indicate that S. paradoxus can help with the removal of proteins from wine. Wines with low protein instability can be stabilized with S. paradoxus as well as polystyrene and chitosan to a lesser degree. All fining agents except for bentonite show efficiency variability between white and red wines. With an average protein reduction around 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.