70 A.J. Mart ́ınez-Rodr ́ıguez and E. Pueyo
(a) (b)
(c)
Fig. 3A.1LTSEM images of yeast cells after 24 h of induced autolysis in a model wine system.
aSuperficial ultrastructure of a yeast cell.b,cImages of fractured empty yeast cells which have
lost most of their cytoplasmic content during the autolysis (Mart ́ınez-Rodr ́ıguez AJ, Polo MC,
Carrascosa AV (2001) Int J Food Microbiol 71:45–51. Copyright (2001). Elsevier)
However, a smaller amount of cytoplasmic contents were solubilized after 12
months of yeast aging in sparkling wines under autolysis in natural conditions
(Fig. 3A.2). This shows that the autolysis conditions during aging of sparkling wines
elaborated by the traditional method are not optimal and it may take several months
or years before this is finished.
3A.4.2 Products Released by Yeast into Wine During Autolysis
Most studies carried out on the transformations taking place during the aging of
sparkling wines elaborated by the traditional method have focused on analysing the
compounds released by the yeast into the wine. Among them, nitrogen compounds