# Yeast Starter Culture Identification to Produce of Red Wines with Enhanced Antioxidant Content
## 4 Discussion  
This investigation marks the first instance of analyzing an autochthonous starter culture collection, with the aim of selecting and characterizing strains exhibiting a low capacity to adsorb polyphenols onto their cell walls. This study establishes selection criteria based on the final concentration of total polyphenols and antioxidant capacity in wine samples obtained at the end of the various experimental phases. Previous studies analyzed polyphenic variation was by evaluating parameters such as color intensity and shade of the yeast colonies post-fermentation, quantified using empirical criteria [37]. We developed a selection protocol based on the evaluation of the residual polyphenic component and antioxidant activity in wines fermented with the strains under analysis, employing Folin-Ciocalteu and TEAC assays. A total of 136 _S. cerevisiae_ starter strains were chosen from the CNR ISPA microbial collection, and their capacity to enhance the polyphenic content in produced wines was evaluated by laboratory-scale fermentation analysis. The results indicated that all strains decreased the concentration of polyphenic compounds and, consequently, the antioxidant power. The top-performing strains, demonstrating a lower capacity to adsorb polyphenols, were selected and characterized throughout the various phases of the study. It is known from the literature that yeast's enzymes (pectinase and glycosylades) may affect polyphenic extraction, modifying the chemical structure of glycosylated phenolic molecules [38]. Moreover, polyphenols interact with yeast by binding to cell wall manoprotein [9]. The observed decrease in TPC and antioxidant activity is likely related to these interaction mechanisms between polyphenols and yeasts. These interaction mechanisms are related also to the variation of the polyphenic profile described in Table 4 as hydrolysis process during winemaking alters the rate between free and glycoside forms of phenolic compounds. Our results confirmed the data obtained by [PERSON] et al. [39], who investigated the properties of wines produced by separate inoculation of _S. cerevisiae_ strains into the same must. The study highlighted strain-specific abilities to differentially adsorb polyphenols during the unification process. Similar results were obtained by [PERSON] et al. [40] on Vranec and Merlot wines in Macedonia, emphasizing the strain-specific influence on the concentration of trans-resveratrol and antioxidant activities. The use of different  
Figure 3: Two-dimensional Principal Component Analysis (PCA). Scoresplot (**A**) for the nine wines and (**B**) loading plot for Volatile Organic Compounds. yeast strains also demonstrated varying polyphenolic content in Pinot Noir wines [13]. Indeed, five different yeast starters were tested in several vinications, in which the _S. cerevisiae_ strain RC212 was able to significantly increase the concentrations of total pigments, anthocyanins and tannins. [PERSON] and associates [41] demonstrated that different yeast strains were able to produce Albarino wines characterized by a specific polyphenolic composition. The above results were further confirmed by a recent report [21], in which an unequivocal correlation between the yeast used to promote the fermentation process and the chemical profile of the wine was recognized, thus underlining the strain-specific abilities of yeasts to modify the color and polyphenolic composition of the final product. Furthermore, a recent study identified yeast starter cultures capable of improving the quality of wine produced from the Italian red cultivar 'Gaglioppo', a cultivar with reduced anthocyanin synthesis [42]. Again, the evidence obtained further highlighted the specific ability of some strains to modify the final amounts of total anthocyanin, total polyphenols and total tannins. Recently, [PERSON] et al. [43] highlighted a positive role of indigenous yeast cultures in improving polyphenol content across the industrial production of Negroamaro and Primitivo wines.