Monitoring viable yeast populations using flow cytometry in spontaneous and inoculated alcoholic fermentations of white must and red mash
摘要
The study investigated the accuracy and precision (repeatability) of flow cytometry (FCM) in combination with fluorescein diacetate and propidium iodide staining for monitoring viable yeast populations during spontaneous and inoculated alcoholic fermentation (AF) of Chardonnay (white) must and Žametovka (red) mash in comparison to the reference plate count method. Prior to must and mash analysis, the accuracy and precision of the FCM method was evaluated during AF of single cultures of Saccharomyces cerevisiae, Hanseniaspora uvarum and Starmerella bacillaris in the lag and exponential growth phases. The results show that the FCM method is a precise (CV between 1 and 7%) and accurate method for the enumeration of S. cerevisiae and non-Saccharomyces yeasts in single cultures. High Concordance Correlation Coefficient (> 0.93) and high agreement in Bland-Altman analysis (mean difference = − 0.02 to 0.04 log10 cells) between the FCM and the reference plate count method was also observed when viable cells were counted during spontaneous and inoculated AF of white must and red mash. However, the type of AF which differed in a diversity of yeast genera, led to a slightly, but not significantly lower accuracy and precision of the FCM method in spontaneous AF of red mash. In conclusion, the FCM method for monitoring AF under real winemaking conditions is fast, precise and reliable method for enumerating viable yeast cells and therefore represents a good alternative to the time-consuming traditional plate count method for routine analysis in the wine industry or under experimental conditions.