94 R. Peinado and J. Mauricio
Finowines are only produced by biological aging. The aerobic metabolism of
flor yeasts causes changes in the aroma fraction that endows them wine with their
typical flavour. In addition, they protect these wines against browning and allow
them to retain their pale colour for years.
Olorosowines are only obtained by oxidative aging, which is accomplished by
fortifying the initial wine to an ethanol content of about 18 vol.% in order to prevent
growth of flor yeasts. Under such conditions,olorosowine acquires a dark colour
by effect of the oxidation of phenol compounds.
Amontilladowines are obtained in a two-step process involving biological aging
under the same conditions to those offinowines, followed by fortification and
oxidative aging as inolorosowines.Amontilladowines are thus the oldest and most
valued of the three sherry types by virtue of their acquiring a more complex flavour
than the other two.
Differences in aroma between biologically and oxidatively aged wines become
even more marked when the wines are compared in terms of sensory properties.
Thus,finowines are clear, bright and light in the glass, and possess a straw yellow
colour with olive-like hues. Also, they are pungent, almondy in the nose, and are
easily recognized by their yeast or bread odour.Olorosowines are dark mahogany
in colour and possess an aroma of balsamic, freshly cracked nut with spicy notes.
Because they are subjected to two types of aging (biological and oxidative),amon-
tilladowines are very complex in terms of sensory properties. Thus, they possess
and amber, yellowish brown colour, and an aroma of dried fruits such as hazel nut
with strong balsamic and spicy notes.
Some authors (Peinado et al. 2004a, 2004b; Zea et al. 2007) have grouped aroma
compounds in aromatic series based on their aroma descriptors. The overall value
for each series is obtained by combiningthe odour activity value (OAV, which is
defined as the ratio of the concentration of a compound to its perception thresholds)
of the individual aroma compounds in the series. The combination of individual
OAVs in order to calculate the overall value for a series cannot be interpreted as an
arithmetic addition of odorant sensations. Some aspects of this classifying scheme
can be subject to criticism, but in any case, the scheme is effective for comparing
wines obtained with different aging methods inasmuch as the odour series always
comprise the same compounds.
Figure 3B.5 shows the odour profiles of three wines as obtained using the OAV
classification scheme. The example illustrates the differences between three types of
wine in terms of volatile components, which have been classified into seven aroma
series.
3B.5 Acceleration of Biological Aging
As noted earlier, biological aging is necessarily a slow process as it involves storing
wine in vast cellars over long periods of time and performing many operations,
such as several rocios per year to ensure homogeneity and quality of the wine,
and control analyses. This substantially raises the production costs of sherry wines,