Sauvignon blanc wine protein stability as affected by pH adjustment and timing of bentonite addition

Abstract

The effects of pH adjustments on Sauvignon Blanc wine protein haze formation and the required amount of bentonite were investigated at both micro-scale 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 utilized 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 (CBB) assay, lithium dodecyl sulfate polyacrylamide gel electrophoresis (LDS-PAGE), and sodium dodecyl sulfate capillary gel electrophoresis (SDS-CGE). 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 each 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, necessitating lower bentonite dosages for stability. Bentonite addition during fermentation proved to be the 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 with high pH juice.