Hides and skins for food and sausage
casings
Gelatin extracted from animal skins and
hides can be used for food. The raw
material can also be rendered into lard. In
the United States and some Asian countries,
pork skin is immersed, boiled, dried and then
fried to make a snack food (pork rinds).
Collagen from hides and skins also has a role
as an emulsifier in meat products because it
can bind large quantities of fat. This make it
a useful additive or filler for meat products.
Collagen can also be extracted from cattle
hides to make the collagen sausage used in
the meat industry.
Collagen casing products were developed
in Germany in the 1920s, but only gained
popularity in the United States in the 1960s.
The processing does not convert the collagen
into a soluble product, as in the case of
gelatine. Instead, it results in a product
which retains a relatively high degree of the
native collagen fiber, and is strong enough to
be used as a casing for sausages and other
products. The extracted collagen is mixed
with water and converted into a dough, which
is extruded by either a wet or a dry process.
The tube of extruded collagen is then passed
through a concentrated salt solution and a
chamber of ammonia to precipitate the
collagen. The swollen gel contracts to
produce a film of reasonable strength. It can
be improved by the addition of glycerin, to
make it more flexible. The tube is then dried
to a 10.0 - 15.0% water content.