28 Biochemistry of Fermented Meat 649in water activity. The length of the ripening/drying
period takes from 7 to 90 days, depending on many
factors, including the kind of product, its diameter,
dryness degree, fat content, desired flavor intensity,
and so on. The reduction in awis slower in beef-
containing sausages. The casing must remain
attached to the sausage when it shrinks during dry-
ing. In general, long-ripened products tend to be dri-
er and more flavorful.
PHYSICALCHANGES
The most important physical changes during fermen-
tation and ripening/drying are summarized in Figure
28.6. The acidulation produced during the fermenta-
tion stage induces protein coagulation and thus
some water release. The acidulation also reduces the
solubility of sarcoplasmic and myofibrillar proteins,
and the sausage starts to develop consistency. The
drying process is a delicate operation that must
achieve an equilibrium between two different mass
transfer processes, diffusion and evaporation (Bal-
dini et al. 2000). Water inside the sausage must dif-
fuse to the outer surface and then evaporate to the
environment. Both rates must be in equilibrium
because a very fast reduction in the relative humidity
of the chamber would cause excessive evaporation
from the sausage surface that would reduce the
water content on the outer parts of the sausage, caus-
ing hardening. This is typical of sausages of large
diameter because of the slow water diffusion rate.
The cross section of these sausages shows a darker,
dry, hard outer ring. On the other hand, when the
water diffusion rate is much higher than the evapora-
tion rate, water accumulates on the surface of the sau-
sage, causing a wrinkled casing. This situation may
happen in small diameter sausages being ripened in
a chamber with high relative humidity. The progress
in drying reduces the water content, up to 20%
weight loss in semidry sausages and 30% in dryFigure 28.6.Scheme showing important physical changes during the processing of fermented meats.