New perspectives in safety and quality enhancement of wine through selection of yeasts based on the parietal adsorption activity (intervento orale)

The removal of ochratoxin A from wine is a pressing problem and many materials have been tested for this purpose. Yeasts represent a very promising biomaterial, also considering their role in the vinification process. The latest results demonstrate the possibility of greatly reducing the ochratoxin A content with expressly selected wine yeasts sequestering the toxin during winemaking. Yeast mannoproteins play a considerable role in this adsorption, due to the mycotoxin-binding capacity demonstrated for modified mannanoligosaccharide derived from the cell wall of Saccharomyces cerevisiae; moreover, the spontaneous nature of ochratoxin A adsorption on yeast cell walls has been recently demonstrated. Yeasts interact with wine colour by anthocyanin-β-D-glucosidase activity, by producing reactive metabolites, by releasing mannoproteins and different polysaccharides and, principally, by retaining pigments on cell walls. The process of parietal adsorption of colour and other phenolic compounds during winemaking has important consequences for wine quality because of the amount of pigment removed. There is a great variability in the wine colour adsorption aptitude of wine yeasts; accordingly, anthocyanin adsorption by yeasts was recently proposed as a criterion for expressly selecting yeasts able to increase or decrease the colour of wines. The latest results also demonstrate the importance, in red winemaking, of selecting yeasts with a low adsorption profile regarding red-bluish pigments, because, currently, bluish hues are highly valued in the production of red wine of superior quality. Further research needs to be carried out to study the adsorption activity of neutral and acid yeast mannoproteins on different compounds present in wine.