Comparison of fermentative properties of some yeasts for must fermentation

Although selected strains of Saccharomyces cerevisiae yeast species, purchased from microbiological colections or from specialized wine yeast producers, are most often used in wine production, some other yeasts species and genus could be used as well. Besides, in the last few years, there has been an increasing use of autochtonous yeasts for controlled must fermentation, isolated from grapes of specific varieties and specific wine region. Selection of a good yeast strain having desirable properties, especially fermentative ones, is prerequisite for quality wine production. Because of limited availability of must throughout the whole year, and its significant composition variations caused by geographycal and climate differencies, we selected chemically defined and easy available medium for comparison of fermentative strain properties. The fermentations were done at 12 and 20 ^oC using different yeasts: ZIM 1900 (identified as Saccharomyces cerevisiae, previously isolated from Cabernet Sauvignon grapes) ZIM 1899 (isolated from Chardonnay grapes and identified as Torulaspora delbrueckii, which was classified before as Saccharomyces rosei), Saccharomyces bayanus strain Z-2 (Collection of microorganisms of Faculty of Food Technology and Biotechnology, Zagreb, Croatia) and two comercial strains of wine yeast, denominated A and B. Fermentation profiles were monitored by measuring mass of released CO_2 and CO_2 production rate. At the end of fermentation, concentrations of reducing sugars, alcohol, total and volatile acidity were determined in centrifuged samples of fermented medium. Results are compared and discussed regarding strain specificities.