Potential of non-<i>Saccharomyces</i> yeast for improving the aroma and sensory profile of Prokupac red wine

This work aimed to analyse the effect of non-Saccharomyces yeasts on the volatile composition, aromatic profile and sensory properties of wine made from autochthonous Serbian grape variety Prokupac (Vitis vinifera). Fermentation was performed with two commercial yeasts, Metschnikowia pulcherrima and Torulaspora delbrueckii, in pure and sequential fermentation with Saccharomyces cerevisiae. The standard analysis of produced wines indicated that the application of both non-Saccharomyces yeast (in pure or in sequential fermentation) significantly reduces the content of alcohol when compared to the control. The use of M. pulcherrima in both pure and sequential fermentation resulted in a higher content of different groups of polyphenols, anthocyanins and flavonoids or better colour characteristics compared to the wines obtained in fermentations with T. delbrueckii. HS-SPME GC/MS analysis revealed the presence of 27 different compounds in the wine samples, with higher alcohols and ethyl esters being the most dominant. It was proven that the presence of non-Saccharomyces yeasts in the initial stage of fermentation with later inoculation with S. cerevisiae contributes to increased complexity of the wine, as well as increased higher alcohol content and total extracts. Wines produced from sequential fermentation with T. delbrueckii showed floral and spice attributes, probably due to 1-pentanol and 2-phenylethanol detected in the wine, as well as to the large amount of ethyl acetate. The use of M. pulcherrima in pure fermentation resulted in wines with the lowest sensorial characteristics (i.e., lacking fruity and floral aroma) probably due to the lowest relative contribution of ethyl esters. The control wine in this study (from pure fermentation with S. cerevisie), had the most intense ‘red berries’ and ‘black berries’ note and low intensity of spices or vegetable aroma, which may be explained by the highest relative contribution of ethyl octanoate and ethyl decanoate. The PCA results also clearly differentiated the analysed samples produced in the sequential, pure and control fermentation trials, leading to the conclusion that the aromatic profile of Prokupac wines produced in sequential fermentation was more complex compared to the wines produced in pure fermentation.