Wenfeng Hung, Roland Harrison, James Morton, Mike Trought, Andy Frost, and Bin Tian*
*Lincoln University, Ellesmere Junction Road, Lincoln, 7647, New Zealand (bin.tian@lincoln.ac.nz)

The effects of pH adjustments on Sauvignon blanc wine protein haze formation and the required amount of bentonite were investigated at both microscale and commercial scale, using identical juice. Additionally, three different timings for bentonite addition were examined during the pH adjustment trial: before, during, and after fermentation. The study used the hot and cold test to determine the bentonite requirement for protein stabilization. Wine proteins were analyzed using various techniques, including a modified Coomassie brilliant blue assay, lithium dodecyl sulfate polyacrylamide gel electrophoresis, and sodium dodecyl sulfate capillary gel electrophoresis. Findings revealed that lower juice pH levels (2.80 and 3.00) resulted in sluggish fermentation, while the presence or absence of bentonite during fermentation did not significantly alter fermentation kinetics at any pH level. Bentonite remaining in contact with ferment improved fermentation completion for the sluggish ferment (pH 2.80). Wines with lower pH exhibited reduced wine protein content and enhanced protein adsorption efficiency of bentonite fining, requiring lower bentonite dosages for stability. Bentonite addition during fermentation proved most effective in protein removal, while fining after fermentation required the least overall bentonite dosage. Although different fermentation scales minimally affected wine protein contents, they did not alter molecular weight (MW) profiles. The protein contents and MW profiles in stabilized wines were influenced by the original juice pH, displaying more complex patterns in high-pH juice.

Funding Support: Lincoln University