A review. Biochemical and molecular mechanisms in <em>Saccharomyces cerevisiae</em> that are involved in the formation of some volatile compounds in wines

There are evidences that a grape must of a non aromatic vine, not having perfume and revealing by gaschromatographie only some classes of compounds common to the musts of all the vine varieties, can originate a pool of characterizing fragrant substances after contact with the yeast during fermentation. Therefore, despite the scarce scientific knowledge available on biochemical mechanisms involved in Saccharomyces cerevisiae in the formation of a wine aromatic pattern, it can be likely hypothesized that the yeast could be the biological motor of this aromatic transformation. The yeast can act on the compounds of the must with many periplasmic enzymes (estérases, glycosidases, lyases, lipases, proteases, peptidases, pectolytiques) and several are the scientific contributions underlining the existence of an interaction between the yeast and the vine variety in the formation of wine aromatic characteristics. Besides the individual contribution of substances sensorially active, the yeast would contribute to the transformation of unknown varietal aromatic precursors that are in the grape skins and/or musts. The biochemical, genetic and physiological aspects of this transformation still have to be understood. At the end, we have to answer some important questions such as the mutual role that grape and/or yeast enzymes have during and soon after crushing in the liberation of the varietal precursors and in the conversion of these in fragrant compounds