Effect of mixed culture fermentations on yeast populations and aroma profile

The effect of pure and mixed inocula on synthetic grape must fermentation has been determined on the fermentation rate and the main characteristics of the wine produced, the volatile profile, amino acid consumption and yeast population dynamics. Three yeast species were assayed: Saccharomyces cerevisiae, Hanseniaspora uvarum and Candida zemplinina. The proportion of mixed cultures was 90:10 between Non-Saccharomyces and S. cerevisiae. The population dynamics was followed by plating, microscope counting and QPCR. The aromatic profile was determined by GC, whereas amino acid consumption was determined by HPLC. All the fermentations in which S. cerevisiae was present were faster and were conducted by this species. S. cerevisiae was also the most effective at converting amino acid consumption into biomass. This effectiveness could be a mechanism for taking over other species during alcoholic fermentation. However, it produced the lowest levels of aromatic compounds. (C) 2012 Elsevier Ltd. All rights reserved.