Improved Screening Method for the Selection of Wine Yeasts Based on Their Pigment Adsorption Activity

The aim of this research is to improve an existing low-cost and simple but consistent culturing technique for measuring the adsorption of grape skin pigments on yeasts, comprising: (i) growing yeasts in Petri dishes on chromogenic grape-skin-based medium, (ii) photographing the yeast biomass, (iii) measuring its red, green, and blue colour components, and (iv) performing the statistical analysis of the data. Twenty strains of Saccharomyces cerevisiae were grown on different lots of the chromogenic medium, prepared using grape skins from dark cultivars Greco Nero, Magliocco and Nero d'Avola. Microscale wine fermentation trials were also performed. Wide and significant differences among wine yeasts were observed. The chromogenic grape-skin-based medium can be prepared using any grape cultivar, thus allowing the specific selection of the most suitable strain of Saccharomyces cerevisiae for each grape must, mainly for red winemaking. The research provides a useful tool to characterize wine yeasts in relation to pigment adsorption, allowing the improvement of wine colour.