Effects of So2 on Fermentation Rates
Effects of SO2 On Fermentation Rates
Purpose
SO2 is the primary inhibitor for natural microbiological growth in wine. It prevents the browning of juice by inhibiting phenol oxidase activity and kills the natural yeast cells for the utilization of fermentation-controlled commercial Saccharomyce strands (Boulton et al. 1996). SO2 is pH and temperature dependent and can exist as several forms. The bisulfate form (HSO3-) can complex with soluble solids such as anthocyanins and acetaldehydes to become bound. Unlike free SO2, the bound bisulfite form possesses no antimicrobial properties but can hydrolyzed with a strong base if conditions are acidic (Ebeler 2012). Due to an immense amount of variation in fruit and wine styles, there is no exact concentration of SO2 ideal for every wine. Previous studies indicate levels of 25 to 75 parts per million will result in 75 to 97 percent inhibition of oxidation (Amano et al. 1979). The purpose of this experiment is to examine different treatments of SO2 concentrations on natural fermentations to understand their effects on sugar depletion rates and to determine the lowest level of SO2 that is still inhibitory for microbiological growth.
Hypothesis: Uninoculated juices with low to no SO2 additions will ferment rapidly with the natural Saccharomyces cells on the grape skins and possibly spoil or develop off-flavors due to a lack of protection against oxygen. Uninoculated juices with high SO2 concentrations may not ferment at all, since the SO2 kills the natural yeast cells. These higher concentration treatments may have a large detectable presence of sulfites, making them unappealing to the senses.
Materials and Methods
All materials and methods were followed according to the laboratory manual (Bisson, 2006) unless otherwise stated.
7,433 pounds of Chardonnay grapes were harvested from the RMI and Tyree vineyard with a field brix reading of 23.9 and 22.9 Brix and pH of 3.54 and 3.65 respectively. The grapes were
Purpose
SO2 is the primary inhibitor for natural microbiological growth in wine. It prevents the browning of juice by inhibiting phenol oxidase activity and kills the natural yeast cells for the utilization of fermentation-controlled commercial Saccharomyce strands (Boulton et al. 1996). SO2 is pH and temperature dependent and can exist as several forms. The bisulfate form (HSO3-) can complex with soluble solids such as anthocyanins and acetaldehydes to become bound. Unlike free SO2, the bound bisulfite form possesses no antimicrobial properties but can hydrolyzed with a strong base if conditions are acidic (Ebeler 2012). Due to an immense amount of variation in fruit and wine styles, there is no exact concentration of SO2 ideal for every wine. Previous studies indicate levels of 25 to 75 parts per million will result in 75 to 97 percent inhibition of oxidation (Amano et al. 1979). The purpose of this experiment is to examine different treatments of SO2 concentrations on natural fermentations to understand their effects on sugar depletion rates and to determine the lowest level of SO2 that is still inhibitory for microbiological growth.
Hypothesis: Uninoculated juices with low to no SO2 additions will ferment rapidly with the natural Saccharomyces cells on the grape skins and possibly spoil or develop off-flavors due to a lack of protection against oxygen. Uninoculated juices with high SO2 concentrations may not ferment at all, since the SO2 kills the natural yeast cells. These higher concentration treatments may have a large detectable presence of sulfites, making them unappealing to the senses.
Materials and Methods
All materials and methods were followed according to the laboratory manual (Bisson, 2006) unless otherwise stated.
7,433 pounds of Chardonnay grapes were harvested from the RMI and Tyree vineyard with a field brix reading of 23.9 and 22.9 Brix and pH of 3.54 and 3.65 respectively. The grapes were
Cited: Borderlon, B., R. Linton. 2010. SO2 Management. Purdue University. www.MoreWine.com Boulton, R.B., V.L. Singleton, L.F. Bisson, and R.E. Kunkee. 1996. Principles and Practices of Winemaking. Chapman & Hall, New York. Buechenstein, J.W., C.S. Ough. 1978. SO2 Determination by Aeration-Oxidation: A Comparison with Ripper. Am. J. Enol. Vitic. 29: 161-164. Ebler, S.E. 2012. VEN 123L Analysis of Musts and Wines: Laboratory Manuel. Lab#3 Sulfur Dioxide. p. 86. Weeks, C. 1969. Production of Sulfur Dioxide-Binding Compounds and of Sulfur Dioxide by Two Saccharomyces Yeasts. Am. J. Enol. Vitic. 20: 32-39.