Alternatives to Bentonite
Use of bentonite as a protein stabilizing agent for wine generates significant lees and results in the loss of flavor or aroma characteristics. An alternative to bentonite such as acid protease treatment would not lead to significant lees nor would non-proteinaceous materials be affected. The biochemical characteristics of proteins leading to haze formation are not yet known. Haze could result as a consequence of insolubility due to proteins with isoelectric points at or near the pH of wine, or to hydrophobic interactions among denatured proteins. Ethanol may reduce the solubility of glycosylated proteins. Ethanol also results in loss of solubility of polysaccharide material, also causing a haze. Hazes may arise for different reasons in different wines. Proteins of varying isoelectric points as predicted from retention time on ion exchange chromatography can lead to haze in wine. This was determined from an analysis of the protein composition of the haze material as well as from analysis of the haze forming potential of proteins separated from wines then subjected to heat treatment. Proteins with an isoelectric point near to the pH of wine were previously thought to be largely responsible for haze formation. Earlier results from our laboratory agreed with this finding. However, our studies of this past year suggest otherwise, but need to be confirmed using other juices. It is likely that the factors leading to haze formation vary depending upon the juice and seasonal variation. In any event, haze formation is a complex chemical process.