Role of bentonites in the prevention of Saccharomyces cerevisiae adhesion to solid surfaces

摘要

Mask (adherent yeast deposit) formation during the industrial processing of champagne wines is an aleatory phenomenon, usually prevented by the addition of bentonites to the wine. The use of such additives is empirical and sometimes inefficient. In order to understand the origin of mask formation and the role of the bentonites, we studied Saccharomyces cerevisiae adhesion to hydrophobic and hydrophilic surfaces (fluoroethylenepropylene, polystyrene, polycarbonate, glass) from two suspending liquids (wine and a solution of KNO_3 (6 x 10~(-2) mol l~(-1))), and the influence of clays on this adhesion. It was shown that Saccharomyces cerevisiae CIVC 8130 and CIVC 7309 adhesion is substratum-dependent and driven by the balance between the dispersive and polar components of the surface free energy (γ_S~d and γ_S~p) respectively and not by the total surface free energy (γ_S) of the substratum. The addition of bentonites to the suspending medium, at concentrations used in the champagne wine process, leads to a clear decrease of yeast adhesion but did not eliminate it completely. Considering the experimental data, it was supposed that there is association between the cells and the clay particles and that the bentonite-yeast aggregates formed do not adhere to solid surfaces. Nevertheless, the bentonites cannot collect all the cells; those remaining in suspension may adhere to the surfaces and be the origin of the formation of an adherent deposit (mask).