Alternatives to Bentonite
Bentonite is the most effective, reliable treatment to achieve protein stability of wine. However, bentonite has a tendency to over-fine and strip wine of constituents important for complexity and can result in a significant loss of wine volume as lees. Disposal of waste bentonite is also a problem. For these reasons, an alternative to bentonite is desirable. Acid proteases should be effective at the selective degradation of proteins in wine, would not generate any lees and will not strip wine of positive characteristics. Commercially available proteases are not effective agents for protein stability. We have been examining the activity against wine proteins of proteases produced by yeasts with a normal habitat of grape juice. These proteases should have evolved towards being active against the proteins of their natural environment. In addition, we have been characterizing the proteins causing haze, as a specific subset of proteins, not total or all wine proteins, are responsible for haze formation. This grant is a continuation of these studies with the specific goals of purifying and characterizing haze causing proteins from Chardonnay, examining the effectiveness of bentonite treatment of grape juice rather than finished wine, exploring the nature of the polysaccharides causing polysaccharide haze and genetic construction of a strain of Saccharomyces secreting an acid protease.