Production of volatile compounds by mixed cultures of Pichia guilliermondii and Saccharomyces cerevisiae

During fermentation it was necessary to evaluate the united interactions in the metabolic activity of Saccharomyces cervevisiae x Saccharomyces uvarum (S6u) and Pichia guilliermondii, yeast which was present on the grapes in different proportions at the time of harvest. The results highlight the fact that Pichia guilliermondii strongly influences the fermentation process and the total metabolic result. For this reason, the presence of Pichia guilliermondii which is on the grapes at the time of harvest needs to be evaluated closely due to the fact it is competitive against Saccharomyces and it is important to note a velocity of sugar fermentation which is inferior to Saccharomyces. For optimal regulation of fermentation it is necessary for the technician to detect Pichia guilliermondi presence in musts. The massive presence of Pichia guilliermondii at pressing leads to slowing down or stoppage of fermentation and the production of high concentrations of benzyl alcohol and acetoin; it is therefore important to use healthy grapes at harvest and filtering the must if necessary to reduce the presence of Pichia guilliermondii.