Yeast starter culture identification to produce of red wines with enhanced antioxidant content

Grape variety, quality, geographic origins and phytopathology can influence the amount of pol-yphenols that accumulate in grape tissues. Polyphenols in wine not only shape their organolep-tic characteristics but also significantly contribute to the positive impact that this beverage has on human health. However, during the winemaking process, the total polyphenol content is substantially reduced due to the adsorption onto yeast wall polymers and subsequent lees sepa-ration. Despite this, limited information is available regarding the influence of the yeast starter strain on the polyphenolic profile of wine. To address this issue, a population consisting of 136 Saccharomyces cerevisiae strains was analyzed to identify those with a diminished ability to ad-sorb polyphenols. Firstly, the reduction in the concentration of polyphenolic compounds associ-ated to each strain was studied by assaying Total Phenolic Content (TPC) and Trolox Equivalent Antioxidant Capacity (TEAC) in the wines produced by micro-scale must fermentation. Twenty-nine strains exhibiting a TPC and TEAC reduction <= 50%, when compared to that detected in the utilized grape must were identified and the nine most-promising strains were further validated by larger-scale vinification. Physico-chemical analyses of the resulting wines led to the identifi-cation of four strains, namely ITEM6920, ITEM9500, ITEM9507 and ITEM9508 which showed, compared to the control wine, a TPC and TEAC reduction <= 20 in the produced wines. They were denoted by a significant (p < 0.05) increased amount of anthocyanin, quercetin and trans coutaric acid , minimal volatile acidity (< 0.2 g/L), absence of undesirable metabolites and a well-balanced volatile profile. As far as we know, this investigation represents the first clonal selec-tion of yeast strains aimed at the identifying "functional" fermentation starters, thereby ena-bling the production of regional wines with enriched polyphenolic content.