Selection and improvement of wine yeasts

Abstract- The selection of wine yeasts is usually carried out within the species Saccha-romyces cerevisiae. It aims at identifying the yeast strains that, besides fermenting grape juice vigorously and producing high ethanol yield, can also positively influence the com-position and the sensorial characteristics of wine. The natural availability of yeast strains possessing an ideal combination of oenological characteristics is highly improbable. Moreover, selected S. cerevisiae wine strains usually produce wines with a plain aromatic profile. The extension of the selection of wine yeasts to S. cerevisiae not growing in oeno-logical environments or to non-Saccharomyces yeasts has provided strains possessing novel and interesting oenological characteristics. Nevertheless, these strains cannot be directly used as starter cultures in wine fermentations, mainly because they are not vigo-rous or competitive in oenological conditions. Wine strains possessing innovative oenolo-gical traits that can influence the sensorial characteristics of wine can be constructed using genetic or molecular methods. Intraspecific S. cerevisiae hybridisation has provided useful oenological strains. Nevertheless, the traits of oenological interest that can be exchanged or introduced using this technique are only those commonly found in the species S. cerevisiae