Alternatives to Bentonite

In this grant year, we have nearly completed the analysis of genetically engineered wine strains of Saccharomyces over-expressing Protease A. The over-expression of Protease A does not lead to release of protease into the medium as is found in laboratory strains under laboratory conditions. We are in the process of determining if the vacuolar level of protease A activity is higher or not in these strains. MALDI and SELDI-TOF analyses are allowing characterization of wine proteins, and, more importantly, direct analysis of wine hazes, sediments and precipitates. The analysis of hazes has revealed a significant amount of low molecular weight material is present. This has not been previously observed, most likely because other techniques do not allow detection of low molecular weight substances. Protein profiles are similar for wines made form the same varietal, but there are marked seasonal differences in the level of protein present. Wines behave very differently upon aging on yeast lees. In the case sparkling wines from one winery, grape protein was completely degraded within 9 months, while in another winery protein persisted for years during aging. The proteins do not appear to be dramatically different among these wines, suggesting that other factors, such as the yeast used, are critical in proteolysis during aging.