# Yeast Starter Culture Identification to Produce of Red Wines with Enhanced Antioxidant Content
## 4 Discussion
Statistical analysis showed that the use of indigenous strains increased the concentrations of several classes of polyphenols in the wines produced compared to wines made with a commercial strain. It can be asserted that the different ability shown by our yeast strains in complex phenolic compounds on their cell wall is a strain-specific property [44; 45]. The evidence that the four yeast starter-culture identified during this study showed the capacity to adsorb the least amount of all types of anthocyanin is consistent with the evidence demonstrated by previous studies in Spain [10], France [45] and Italy [46]. Therefore, it is imperative to consider the adsorption ability of phenolic compounds during selective procedures for yeasts starter culture in wine production [9]. Nevertheless, it is worthy to note the effect of scale comparing the differences between the performance of the selected strains in reducing TPC between the micro-scale and laboratory-scale vinication. This finding is in agreement with our previous investigation [47], where we explored the enoological significance of winemaking scales in evaluating the contribution of new starter cultures to the chemical profile of produced wine. As regards the volatomic aspect that influences the sensorial quality, our results confirm that the ITEM 6920-9500-9507-9508 strains contribute to a balanced volatile profile, mainly characterized by secondary fermentation products. In particular, ethyl ester concentrations were influenced by the yeast strain, fermentation temperature, degree of aeration, and sugar content. Both ethyl esters and acetate esters have a key importance in the overall aroma of wine, contributing positive sensory notes like sweet-fruity, grape smell, and sweet balsamic [48; 49]. Concerning esters, the mentioned strains showed an increased ester production ofisoamyl acetate, ethyl hexanoate, diethyl succinate, phenyl acetate and mono ethyl succinate. Similarly, among higher alcohols, 2-phenylethanol contributes a floral (pink) aroma [50], but an excess concentration above 300 mg/L would impart a strong and pungent odor and taste [51]. In our study, the use of selected yeast strains allowed us to obtain higher alcohols in concentrations lower than the critical threshold value, with a positive contribution to the sensorial profile, and phenylethanol values higher than the perception threshold (10 mg/L) [52; 53] except for ITEM 9501 and 14093. Finally, the contribution of the volatile acid fraction also appears positive. Indeed, fatty acids, produced during fermentation, constitute an important group of aromatic compounds that can provide fruity, cheesy, fatty, and rancid notes. In this case, the quantified fatty acids had levels lower than their perception threshold. By processing the data obtained at the end of the various experimental phases, we were able to identify four strains (ITEM6920, ITEM9500, ITEM9507, and ITEM9508) capable of producing wine characterized by a higher concentration of total polyphenols, an enhanced antioxidant capacity, and the absence of undesirable metabolites.