Stereodifferentiation of geosmin in wine

Gcosmin (trans-1,10-dimethyl-trans-9-decalol), a well-known, highly odorous compound, has recently been identified and quantified in red and sweet whi te wines, as well as in grape juice before alcoholic fermentation. Geosmin is a chiral compound and the (-) form is much more odoriferous than the (+) form. Enantioselective multidimensional gas chromatography analysis of a p urified Cabernet Sauvignon wine extract revealed the presence of only one e nantiomer: (-) geosmin. In grape juices obtained from rotten grapes and in wines this compound can be found at concentrations much higher than its olf actory perception threshold, indicating that it contributes to their earthy aroma. (-) Gcosmin is also the only enantiomer to have been identified in pure cultures of Streptomyces sp. and Penicillium sp. strains isolated from rotten grapes.