Drying 223- The mechanical and organoleptical pro-
perties of the originally soft material
improve.
Details of the Steps
The water vapor leaves the surface layer of
the product if the a w of the surface layer is
higher than the relative humidity of the air
around the product. In reversed cases, the
surface layer binds water and becomes wet.
The rate of drying depends on:- the measurements of the drying surface
- the difference between the a w and the
humidity of the air (driving force) - the characteristics of the outer layers with
pores (e.g ., casing, mold, surface layer of
the product/drying resistance)
The drying surface is the geometrical
surface multiplied by the ratio of the water -
permeable elements (meat) to the surface.
Ham with skin dries only on the meat side;
the skin side is isolated by the fat. This barrier
effect is utilized during ripening of some
types of hams. If the meat surface is smeared - the characteristic composition of the end
product (water, meat - protein, salt, other
soluble materials, insoluble materials) - a w to be reached.
Meat ’ s a w — which is necessary for stabil-
ity — depends on pH. The higher the pH, the
lower the a w must be (Fig. 11.1 ).
The loss of mass and the initial salt content
can be calculated on the basis of the planned
end characteristics (Fig. 11.4 ).
The next task is to determine the drying
rate. To do this, we need to understand the
drying process.
The Drying Process
During drying
- Water vapor evaporates from the surface of
the product, and consequently, the compo-
sition of the surface layer changes. - Materials move from one layer of the
product to the other. - The thickness (and eventually the shape
too) of the layers changes to different
degrees.
Figure 11.4. Change of a w as a function of water loss and initial salt content of meat products.