The fermentation of apple must is a complex microbial reaction involving the sequential development of various
species of yeasts and bacteria (Beech, 1972; Salih et al., 1988; Cabranes et al., 1990; Duen˜ as et al., 1994). Among
these micro-organisms, yeasts are primarily responsible for alcoholic fermentation. Thus, the different yeast species
developed during fermentation and their dynamics and frequency of appearance determine the taste and flavour
characteristics of products