Handbook of Meat Processing

224 Chapter 11

radius of product is more equilibrated than

the water content. So the salt content com-

pared with the water mass is lower in the

outer layers (Fig. 11.5 ) (K á rp á ti 1960 ; Gou

et al. 2004 ).

In the initial phase of drying, the moisture

content of outer layers decreases, while the

inner layers lose water in the later periods.

The equilibration of water content becomes

slower and slower, which in turn slows down

drying. The differences in water content of

the layers barely changes after the end of

drying (Fig. 11.6 ) (Imre 1974 ).

The mechanical properties of dried meat

products, such as chewiness, easy slicing,

appropriate fi rmness, and suffi cient fl exibil-

ity, are very important. During drying

• the initial plasticity comes to an end.


• the mentioned attributes increase.


• chewiness and sliceability improve.

The fi rmness is highest in the surface layer

as a consequence of the higher content of dry

material (Fig. 11.7 ) (Kov á cs 1961 ; Ruiz -

Ramirez et al. 2005b ). Too low water content

in overdried products causes denaturation of

proteins and a loss of swelling capacity. The

result is a product that is too chewy.

with fat, the ripening process that produces
aroma proceeds with very slow drying.
The geometric surface of chopped prod-
ucts decreases during drying because the
diameter of the rods decreases. The perme-
able part of the surface decreases to a higher
degree than the geometrical surface because
the impermeable fat particles fl atten out,
occupying a greater part of the surface. The
water vapor leaving the surface increases the
moisture content of the ambient air. The rela-
tive vapor content will be higher because the
evaporation cools down the surface and the
environment. The air surrounding the product
has to become drier and warmer to maintain
the driving force.
The high rate of air circulation decreases
the air - side drying resistance too. The prod-
uct - sided resistance depends on the porosity
of the casing, the mold, and the fat fi lm on
the surface. This resistance steadily increases
during the process, lowering the drying rate.
The salt content of the surface layer grows
with the water loss and decreases with the
diffusion of salt into the inner layer. The
driving force of diffusion is the difference in
the salt content compared with the water
content. The diffusion of salt seems to be
quicker because the salt content along the

0

10

20

30

40

50

60

70

80

90

100

0 102030405060708090100

days

moisture content in % of the initial one

r=0 r=50 r=80 r=100

r= distance from the center in % of radius

Figure 11.5. Pattern of moisture content in the layers of salami during drying.