Effects of commercial non-saccharomyces yeasts on quality of wines produced from Emir grapes

The aim of this study was to examine the effects of non-Saccharomyces commercial yeast strains on the chemical and organoleptic properties of wine by using them in the production of wines obtained from Emir grapes to contribute to the literature that has limited information on local grapes and to benefit wine producers for the use of these products in the sector. For this purpose, sequential fermentation was carried out with Saccharomyces cerevisiae, each of the active dry commercial yeasts containing Metschnikowia pulcherrima, Torulaspora delbrueckii, and Metschnikowia pulcherrima / Torulaspora delbrueckii mixture. After 4 months of maturation, chemical (alcohol, total acidity, pH, density, volatile acidity, reducing sugar, total/free SO2), color, and volatile compound analyses with HS-SPME-GC/MS were performed. The wine fermented with a mixture of Metschnikowia pulcherrima / Torulaspora delbrueckii had the best results in sensory analysis. It has been observed that non-Saccharomyces yeasts produced lower alcohol and produced isobutanol, isoamyl octanoate, and octanoic acid, which contributed to the aroma complexity of the wine, unlike wine fermented only with Saccharomyces cerevisiae. The formation of acetic acid and dodecanoic acid, primarily undesirable in wines from Emir grapes which gives a feeling of oiliness, was detected only in wines fermented with Saccharomyces cerevisiae. At the end of the study, it has been proven that non-Saccharomyces yeasts positively affected wine quality by sequential fermentation with Saccharomyces cerevisiae as active dry yeast.