Vintage Effect on the Strain Dependent Dynamics of Ethanol Production in Vineries of Tokaj

Abstract

The dynamics of ethanol production of local strains of three yeast species and their ternary mixtures was examined in two Tokaj vineries. Although, the performance of them diverged significantly in first etaps of vinification—up to the utilization of half of the sugar content of grape juice—the variations vintages per vintages surpassed the strain-dependent alterations. The divergence in the latter aspect diminished during the last etap, and the ethanol concentration in young wines fermented by Saccharomyces cerevisiae , S. uvarum and Starmerella bacillaris (2 local strains of each) and their mixtures did not vary considerably (c.v. 4.2%). The vinification of grape juice performed more rapidly in fermentors inoculated with strains of S. cerevisiae , S. uvarum and St. bacillaris as well as with their mixtures than in spontaneously initiated ones by wild mycoflora in each vintage. The strains responded in different manners to conditions vintage per vintage, however, their ternary mixtures always fermented more intensively the grape juice than the strains alone. The strains affected the dynamics of alcohol production to different extents, but the alterations between them exceeded the variation between the average effects of the species. The circumstances of vinification significantly influenced the subsequent events of fermentation, but the maximum intensity of ethanol production was inversely proportional to the time required to start alcohol production (p > 0.05), similar to that observed in the laboratory under strictly controlled micro-vinification experiments. The maximum intensity of ethanol production (MIE) varied between 0.64 - 2.59 mM ethanol per hour. The coefficients of second-order polynomial equations describing the dynamics of alcohol production in both laboratory micro-scale and me dium-scale experiments in cellars revealed similar correlations regarding the in teraction of factor groups regulating the process: the constant (time- independent) and secondary (time-dependent) coefficients of these polynomes counteracted to the primary (time dependent) ones strictly in the strain-dependent manner, and the role of these three factors groups varied also in a strain dependent manner during the vinification process independently of the varying circumstances in three vintages.