Combined heat and proteolytic enzyme treatment of white wines reduces haze forming protein content without detrimental effect

Laboratory heat treatments of wines at both medium and high temperatures, with and without the addition of proteolytic enzymes have resulted in reduced protein content and bentonite requirements for heat stability. Increasing sulfur dioxide concentration of the wines resulted in additional reductions in protein content after treatment. Pilot scale experiments (50L batches) were done using two proteolytic enzyme preparations and three commercial wines that had not been bentonite fined. Wines with and without enzyme addition were heated at 90°C for 1 minute in a tubular heat exchanger, then immediately cooled to 16°C to 19°C. This combined heat and enzyme treatment reduced the protein levels in all wines to between 40% and 80% of the original levels. Heat treatment alone reduced the protein levels to between 50% and 90%. The bentonite-fining requirement was reduced to between 30% and 60% in the combined heat and enzyme treated wines, compared to the heat alone treatment that reduced the requirement to between 50% and 70%, of the bentonite requirement for the untreated wines. Sensory evaluation of the wines showed that the treatments had negligible effect on aroma and no effect on palate characteristics. There were some slight effects on aroma in some cases from heating and from enzyme addition but the dosage was much higher than that recommended by the enzyme manufacturer. Separate experiments in which wine was heated at 45°C for 1 day gave results similar to those obtained with short term heating at 90°C in respect of reduced bentonite fining requirements.