Analysis of yeast diversity during spontaneous and induced alcoholic fermentations

The diversity of yeast species and strains was monitored by physiological tests and a simplified method of karyotyping of yeast chromosomes. During the first phase of investigated alcoholic fermentations, the yeast species Metschnikowia pulcherrima and Hanseniaspora uvarum were predominant, irrespective of the origin of the grape must. At the beginning of fermentation H. uvarum was even present in the case of induced fermentations with dried yeast. Middle and end phase of the alcoholic fermentation were clearly dominated by the yeast species Saccharomyces cerevisiae . In the case of spontaneous fermentations, several different strains of S. cerevisiae were present and competed with each other, whereas in induced fermentations only the inoculated strain of S. cerevisiae was observed. A competition of strains of S. cerevisiae also occurred during the fermentation with dried yeast product consisting of two different strains. An effect of H. uvarum on taste and flavour of wines can be postulated according to the frequency of its appearance during the first phase of fermentation. With the method of rapid karyotyping and supplementary physiological tests it was possible to make reliable assertions about the yeast diversity during alcoholic fermentation.