Interactions Between Industrial Yeasts and Chemical Contaminants in Grape Juice Affect Wine Composition Profile

Etjen Bizaj^1,2, Chris Curtin², Neža Čadež¹ and Peter Raspor<sup>1,3*

1</sup>University of Ljubljana, Biotechnical Faculty, Chair of Biotechnology, Microbiology and Food Safety, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia
²The Australian Wine Research Institute, P.O. Box 197, Glen Osmond, Adelaide SA 5064, Australia
³University of Primorska, Faculty of Health Sciences, Polje 42, SI-6310 Izola, Slovenia

Article history:
Received November 5, 2013
Accepted April 17, 2014

Key words:
wine fermentation, Saccharomyces spp., interspecies hybrids, pyrimethanil, fenhexamid, ochratoxin A, aromatic profile, fermentation kinetics, H₂S, Sauvignon blanc

Summary:
The interaction between four industrial wine yeast strains and grape juice chemical contaminants during alcoholic fermentation was studied. Industrial strains of Saccharomyces cerevisiae (AWRI 0838), S. cerevisiae mutant with low H₂S production phenotype (AWRI 1640), interspecies hybrid of S. cerevisiae and S. kudriavzevii (AWRI 1539) and a hybrid of AWRI 1640 and AWRI 1539 (AWRI 1810) were exposed separately to fungicides pyrimethanil (Pyr, 10 mg/L) and fenhexamid (Fhx, 10 mg/L), as well as to the most common toxin produced by moulds on grapes, ochratoxin A (OTA, 5 mg/L), during alcoholic fermentation of Vitis vinifera L. cv. Sauvignon blanc juice. Contaminants were found to strongly impair fermentation performance and metabolic activity of all yeast strains studied. The chemical profile of wine was analyzed by HPLC (volatile acidity, concentrations of ethanol, fructose, glucose, glycerol and organic acids) and the aromatic profile was analyzed using a stable isotope dilution technique using GC/MS (ethyl esters, acetates and aromatic alcohols) and Kitagawa tubes (H₂S). The chemical composition of wine with added contaminants was in all cases significantly different from the control. Of particular note is that the quantity of aromatic compounds produced by yeast was significantly lower. Yeast’s capacity to remove contaminants from wine at the end of the alcoholic fermentation, and after extended contact (7 days) was determined. All the strains were able to remove contaminants from the media, moreover, after extended contact, the concentration of contaminants was in most cases lower.

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