Influence of maceration time, SO2 and yeast strain on the content of phenolic compounds in wines from Vranec and Merlot varieties

Red wines from V. vinifera Vranec and Merlot grapes produced using a series of identical fermentation conditions for all wines (maceration times of 3, 6 and 10 days, two doses of sulphur dioxide, 30 and 70 mg/L SO2, and two yeasts for fermentation, Macedonian yeast-Vinalco and French yeast-Levuline) were subject of investigation. The concentration of phenolic acids, anthocyanins and flavan-3-ol monomers was determined by reversed-phase HPLC, while analysis of proanthocyanidins was performed by HPLC after acid-catalysed cleavage in the presence of phloroglucinol. Vranec wines were richer in anthocyanins and hydroxycinnamic acids and showed higher content of condensed tannins in comparison to the Merlot wines obtained under the same technological conditions. Vranec wines reached highest concentrations of anthocyanins after 6 days of maceration, while gradual increase of proanthocyanidins was observed both for Vranec and Merlot wines with increased pomace contact. The highest contents in acylated anthocyanins and proanthocyanidins were found in Vranec wines fermented with French yeast, macerated for 10 days. Differences in the extraction kinetics between the two yeast strains can probably be attributed to differences in their fermentation kinetics. Higher doses of SO2 resulted in increased extraction of all phenolic compounds. Statistical treatments of the data, using cluster analysis and principal component analysis, showed a clear separation of the samples, mainly according to the variety, followed by sub-grouping related to the maceration time and SO2 content