# Yeast Starter Culture Identification to Produce of Red Wines with Enhanced Antioxidant Content
## 3 Results  
A laboratory-scale test was set up in liquid, using natural must, and the capacity of 136 strains from the ITEM Collection to adsorb polyphenols onto their cell wall was subsequently evaluated by chemical assays on the resulting wines. A starter yeast population was then characterized with a total number of 136 strains (Table S1). The adopted procedure included the following steps: establishing of a population of starter yeasts extracted from the ITEM Collection, seedling on a YPD agar plate, preparing liquid cultures in YPD, inoculating selected must, initiating fermentation in triplicate, and assessing the total polyphenic content (TPC). For inoculum preparation, 5 mL of Primitivo must was placed in sterile tubes with a 13 mL volume cap. Each thesis was individually inoculated with a yeast concentration of 0.4 \(\times\) 10\({}^{6}\) CFU/mL. Fermentations were carried out for 15 days, following which the determination of TPC was carried out for each sample using the Folin-Ciocalteu colorimetric assay and quantified as micrograms of gallic acid equivalent per mL (\(\upmu\)gGAE/mL). Upon analyzing the concentrations of polyphenic compounds in the wines produced by each yeast, we identified 29 strains exhibiting a TPC reduction of \(\leq\)50%, when compared to that detected in the utilized grape must. Additionally, the determination of the antioxidant capacity (TEAC), quantified as umol of Trolox Equivalents per mL (umolTE/mL), performed by ABTS\({}^{+}\) colorimetric assay, was also reserved for the wines produced with the above 16 strains (Table 1). In view of the lower reduction of both TPC and TEAC, the strains 83, 84, 86, 99, 105, 106, 112, 113 and 135 were selected for the subsequent experiments. One liter of pasteurized Primitivo must was separately inoculated with 0.4 \(\times\) 10\({}^{6}\) CFU/mL of each of the above nine strains. Fermentations were conducted in triplicate and they took a regular course completing the alcoholic fermentation process in above eight days. The wines were analyzed by Fourier transform infrared spectrophotometry (FT-IR) for the main chemical parameters. Table 2 shows the results of the main physical-oenological and color parameters of the finished product, respectively. The ethanol amounts (g/100 mL) ranged from 11.97 (135) to 11.43 (86). The residual sugar contents determined for all the obtained wines was found in all wines below 2 g/L, a concentration consistent with a completed fermentation. The total acidity (TA) showed an amount varying from 7.50 g/L to 6.76 g/L, whereas the levels of volatile acidity (VA) ranged from 0.10 g/L to 0.14 g/L. As expected, all produced wine showed an acetic acid (VA) concentration \(<\) 0.2 g/L value. The nine selected yeast strain also produced a satisfactory quantity of glycerol, whose concentration ranged ranging from 7.75 to 6.38 g/L. The nine resulting wines were then analyzed by assessing the concentration of total polyphenols (\(\upmu\)gGAE/mL) by the Folin-Ciocalteu colorimetric assay and the antioxidant power (umol TE/mL) through the TEAC assay (Table 3). As expected, the comparison of TPC and antioxidant activity in wines obtained by different yeast strain revealed a positive correlation. When inoculated into a larger volume of must, the nine yeast strains demonstrated a decreased capacity to adsorb wine polyphenol compounds on their external surfaces compared to the results reported in Table 1. Specifically, strains 6920, 9500, 9507, and 9508 exhibited a reduction rate of TPC and TEAC of less than 20%. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**ID**} & \multirow{2}{*}{**Strain**} & \multirow{2}{*}{**TPC (\#gGAE/mL)**} & \begin{tabular}{c} **\%TPC** \\ **Reduction** \\ \end{tabular} & \
\begin{tabular}{c} **TEAC** \\ **(nmolTE/mL)** \\ \end{tabular} &
\begin{tabular}{c} **\%TEC** \\ **Reduction** \\ \end{tabular} \\ \hline  
ust** & & 1167.45 \(\pm\) 8.46 & & 87.49 \(\pm\) 3.01 & \\ \hline \hline \end{tabular}
\end{table}