74 A.J. Mart ́ınez-Rodr ́ıguez and E. Pueyo
to accelerate the autolytic process during sparkling wine production: adding yeast
autolysates to the wine, and increasing the temperature during aging (Charpentier
and Feuillat 1992). However, both techniques result in organoleptic defects in the
final product, which are often described astoasty. It has recently been suggested that
by using a combination of killer and sensitive yeasts, it should be possible to acceler-
ate the onset of yeast autolysis during sparkling wine production (Todd et al. 2000).
However, the effect of this strategy on the organoleptic properties of wine has not
yet been studied. Tini et al. (1995) also found interesting results by using autolytic
strains derived through meiosis from an industrial second fermentation yeast. In pre-
vious works, we suggested that a yeast strain with a good autolytic capacity would
produce better quality sparkling wine than a yeast with a low autolytic capacity, and
recommended that autolytic capacity be studied when selecting a yeast for sparkling
wine production (Mart ́ınez-Rodr ́ıguez et al. 2001b). Also, Gonz ́alez et al. (2003)
found interesting results by using mutant yeast strains obtained by UV irradiation.
Recently, we showed that one of these mutant yeasts, presenting accelerated autol-
ysis, produced sparkling wines with improved foaming properties compared to the
control strain (Nunez et al. 2005). In this experiment, aging time was reduced from
nine to six months, which could also reduce production costs.
Cebollero et al. (2005) used a yeast mutant defective in the autophagic or the Cvt
pathways to show that autophagy does take place under wine production conditions.
Also, using the depletion of Ald6p as a marker, autophagy has been demonstrated
to take place in commercial second fermentation yeasts during a real sparkling
wine elaboration process (Cebollero and Gonz ́alez 2006). As autophagy is a pro-
cess that precedes autolysis and many of the genes involved in it are well known,
genes related to autophagy could be good candidates to obtain genetic engineer-
ing wine yeast presenting accelerated autolysis. Yeast strains showing increased
rates of autolysis could also be useful, not only for the elaboration of sparkling
wines by the traditional method, but also for the production of still wines aged
on lees, an enological practice that has been increasing in popularity over the past
few years.
3A.5 Conclusions
Sparkling wines are typically classified in relation to the production method by
which they are made. Of these, sparkling wines elaborated by the traditional method
are usually considered to present the best sensory properties. During aging, numer-
ous changes occur while the yeast remainsin contact with the wine, modifying
its sensory characteristics, and the foaming properties of these wines are highly
appreciated. The process takes place slowly and continuously, and the yeast remains
in contact with the wine for prolonged periods of time in order to give the wine
its special characteristics. Morphological and analytical studies on yeast autolysis
in sparkling wines have revealed the major changes produced during yeast autol-
ysis and its implication in wine quality. Although the autolytic process has been
extensively studied, there are still some aspects that remain unclear. This is the