Surface properties of Saccharomyces cerevisiae lees during sparkling wine ageing and their effect on flocculation.

Cell surface properties were determined for the first time for lees of Saccharomyces cerevisiae, and they proved to be significantly dependent on the time of sparkling wine ageing on lees. Cell surface hydrophobicity decreased from approximately 44% to 11% of affinity to hexadecane. Electron acceptor capacity (calculated as % affinity to ethyl acetate-% affinity to decane) increased from approximately -27% to 10 % and zeta potential from approximately -4 to 6mV. Mannoproteins are released from the external cell wall layer during the autolytic process, as confirmed by TOF-SIMS analysis of the cell wall chemical composition. This could explain the modifications of lees cell surface properties observed during ageing. Lees flocculation capacity, calculated by the Helm's method, decreased during the period of ageing from approximately 88 % to 40%. Stepwise multiple regression analysis indicated that lees surface hydrophobicity was the main determinant of lees flocculation capacity, explaining 70.3% of the variability (p<0.01), followed by far by the absolute values of zeta potential, accounting for 9.9% of the variability (p<0.05).