Response to Sulfur Dioxide Addition by Two Commercial Saccharomyces cerevisiae Strains

Sulfur dioxide (SO2) is an antioxidant and antimicrobial agent used in winemaking. Its effects on spoilage microorganisms has been studied extensively, but its effects on commercial Saccharomyces cerevisiae strains, the dominant yeast in winemaking, require further investigation. To our knowledge, no previous studies have investigated both the potential SO2 resistance mechanisms of commercial yeasts as well as their production of aroma-active volatile compounds in response to SO2. To study this, fermentations of two commercial yeast strains were conducted in the presence (50 mg/L) and absence (0 mg/L) of SO2. Strain QA23 was more sensitive to SO2 than Strain BRL97, resulting in delayed cell growth and slower fermentation. BRL97 exhibited a more rapid decrease in free SO2, a higher initial production of hydrogen sulfide, and a higher production of acetaldehyde, suggesting that each strain may utilize different mechanisms of sulfite resistance. SO2 addition did not affect the production of aroma-active volatile compounds in QA23, but significantly altered the volatile profiles of the wines fermented by BRL97.