Yeast lees isolated from wine or a culture medium after fermentation have the particular property of being able to adsorb certain volatile thiols contained in a hydroalcoholic wine-like solution. Yeast cell-walls are also able to adsorb the same thiols when prepared by mechanical disruption of whole cells in the presence of a reducing agent such as dithiothréitol (DTT). Thiols adsorbed in this manner may be re-released from the cell-walls by the addition of DTT in the medium. On the other hand, yeast cell-walls prepared under the same conditions lose their adsorption capacity following hydrolysis with a beta-glucanase preparation able to release mannoproteins.
These results indicate that volatile thiols combine with the yeast cell-walls by means of disulphide bonds with the cystein contained in mannoproteins.
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