Effect of Wickerhamomyces anomalus and Pichia membranifaciens killer toxins on fermentation and chemical composition of apple wines produced from high-sugar juices.

Killer toxins are proteinaceous compounds that could be considered as a biological alternative to sulphur dioxide for the prevention of wine spoilage by undesirable wild yeasts. The current study investigated the influence of crude killer toxins secreted by Wickerhamomyces anomalus and Pichia membranifaciens strains on the fermentation process and chemical composition of apple wines. The main oenological parameters (ethanol, extract, total sugars, reducing sugars, titratable acidity) of obtained apple wines as well as selected volatile compounds and organic acids were analysed. It was revealed that the application of crude killer toxins to apple juices inoculated with Saccharomyces strains did not significantly change the fermentation kinetics, however, in most of the cases, the apple wines were distinguished by a slightly higher concentration of ethanol compared to the control samples fermented without killer toxins. The volatile acidity of the wines depended on yeast strain used in fermentation rather than on the type of killer toxin. It was also found that the addition of crude toxins slightly changed levels of several aroma components, however, the yeast strains used for the fermentation process contributed considerably to variations in profiles and concentrations of volatile compounds. [ABSTRACT FROM AUTHOR]