Abstract
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.
Highlights
Sulfur dioxide (SO2 ) has been used as an antimicrobial and antioxidant in winemaking for hundreds of years
This study investigated the responses of two different commercial S. cerevisiae strains to the presence (50 mg/L) and absence (0 mg/L, control) of SO2 in terms of fermentation kinetics and yeast-derived volatile secondary metabolites
BRL97 was found to be more resistant to SO2 than QA23, which exhibited decreased growth and a slower fermentation rate when SO2 was added
Summary
Sulfur dioxide (SO2 ) has been used as an antimicrobial and antioxidant in winemaking for hundreds of years. It is added at different times throughout the winemaking process, including prior to inoculation with commercial yeast strains, in order to suppress any potential spoilage microorganisms from the grape must. Different yeast strains may respond differently to SO2 addition, and it is important for winemakers to know which yeasts respond in favourable ways so they may select appropriate strains to use as inoculants. If the level of SO2 added to the must is too high, wine yeasts, including both spoilage yeasts such as Brettanomyces bruxellensis and fermentative yeasts such as S
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