# Response to Sulfur Dioxide Addition by Two Commercial _Saccharomyces cerevisiae_ Strains
## 2 Materials and Methods
### Statistical Analysis  
A standard curve for each compound of interest measured via HS-SPME GC-MS was created in Excel 2016, and a linear line of best fit was applied to each volatile compound of interest. R\({}^{2}\) values above 0.99 were confirmed for all compounds, except ethyl acetate, which had an R\({}^{2}\) value of 0.93 (data not shown). This indicated that no nontarget compounds were being measured along with the compound of interest. \begin{table}
\begin{tabular}{c c c c c} \hline
**Category** & **Metabolite** & **Abbreviation** & **Aroma** & **Threshold (ug/L)** \\ \hline \multirow{8}{*}{Ethyl esters} & Ethyl acetate & EA & fruity, solvent a,b & 7500 \\  & Ethyl propanoate & EP & fruity, solvent a,b & 1800 \\  & Ethyl & E2 MP & Fruity a & 15 \\  & 2-methylpropanoate & EB & apple, strawberry a & 20 \\  & Ethyl & E2 MB & apple, strawberry a & 1–18 \\  & 2-methylbutanoate & EHyl & & \\  & Ethyl & E3 MB & apple, strawberry a & 3 \\  & Ethyl hexanoate & EH & fruity, fermented pear a & 5–14 \\  & Ethyl catanoate & EO & fruity, fatty b & 2 \\  & Ethyl decanoate & ED & Grape b & 200 \\  & Ethyl dodecanoate 1  & EDD & soapy, estery b & 25,619 * \\ \hline \multirow{8}{*}{Acdates} & 2-methylbutyl acetate 2 & 2 MBA & Fruity b & 160 \\  & 3-methylbutyl acetate 2 & 3 MBA & Banana b & 30 \\  & Hexyl acetate & HA & fruity, herby b & 670 \\  & 2-phenylethyl acetate & 2 PEA & rose, honey b & 250 \\ \hline \multirow{8}{*}{Acids} & 2-methylbutanoic acid & 2 MBAcid & butter, cheese b & 1500 \\  & 3-methylbutanoic acid & 3 MBAcid & sweat, rancid b & 33.4 \\  & Hexanoic acid 1  & NA & 420 \\  & Octanoic acid & OA & sweat, cheese a,b & 500 \\  & Decanoic acid & DA & Sour a, rancid/fatry b & 1000–8100 \\ \hline \multirow{8}{*}{Alcohols} & 2-methyl propanol & 2 MP & roasted nuts a, solvent & 40,000 \\  & 2-methylbutanol a & 2 MB & Onion b & 65,000 \\ \cline{1-1}  & 3-methylbutanol a & 3 MB & roasted nuts a, whisky b & 30,000 \\ \cline{1-1}  & Hexanol & HOH & green, floral a,b & 8000 \\ \cline{1-1}  & 2-phenylethanol & 2 PE & honey, spice, floral b & 10,000–14,000 \\ \cline{1-1}  & Benzyl alcohol & Benz & sweet, floral b & 900,000 \\ \cline{1-1}  & Methionol & MOH & cooked potato a & 1000 \\ \hline \end{tabular}
\end{table} 
Table 1: List of yeast-derived secondary metabolites measured, as well as their characteristic aromas and odour detection thresholds in 10% (\(\eta\)%) ethanol ([39; 40; 41; 42; 43; 44], compiled by [45]). Residual sugar, yeast abundance, H\({}_{2}\)S production, and acetaldehyde production data were all statistically analyzed using RStudio (version 3.5.1). Two-factor repeated measures ANOVA were performed to test for differences in residual sugar (g/L glucose + fructose) and yeast abundance (CFU/mL) among treatments throughout fermentation. These ANOVA were performed using the \"aov\" function. When appropriate, Tukey HSD post-hoc tests were performed to conduct pairwise comparisons among treatments using the \"lm\" function in the nlme package, and the \"glht\" and \"cld\" functions in the multcomp package, adjusted for multiple comparisons using the Holm method. The assumption of homogeneity of variance was assessed using the \"levenTest\" function from the car package (version 3.0-0), which indicated a significant difference among treatments for yeast abundance (F (3,93) = 10.1, \(p\) = \(<\)0.001) but not for residual sugar (F (3,220) = 2.04, \(p\) = 0.11). Yeast abundance data were normally distributed, but residual sugar data were not. However, because ANOVA are generally robust to violations of assumptions when sample sizes are equal among groups, no data transformations were performed. The production of H\({}_{2}\)S (ppm) by yeasts in response to SO\({}_{2}\) addition was compared among yeast strains by performing a one-factor repeated measures ANOVA on untransformed data using the \"aov\" function. As no H\({}_{2}\)S was produced in the 0 mg/L treatments, these samples were removed from analysis.