Agriculture Reference
In-Depth Information
4
Preservation of meat
The primary purpose of food preservation is to prevent
food spoilage. Whether food spoilage is mild or extreme,
the primary cause is the action of micro-organisms -
bacteria, moulds or yeasts - aided by enzymes. As living
organisms, they can survive and develop only under
particular environmental conditions; under unfavoura-
ble conditions, they die or at least fail to develop.
The underlying principle of all food preserving methods,
therefore, is the creation of conditions unfavourable to the
growth or survival of spoilage organisms by, for example,
extreme heat or cold, deprivation of water and sometimes
oxygen, excess of saltiness or increased acidity. The methods
by which meat foods may be preserved are drying, curing,
cold, heat, chemicals, irradiation and high pressure.
Preservation by
chemicals
may be achieved by, for
example, the addition of sulphur dioxide to foodstuffs
such as fresh sausage, but this and the use of other
chemicals are greatly restricted by food regulations in
most countries, although research continues to find an
acceptable chemical means of preservation.
Chemical preservation can also be achieved by
smoking of meat and fish usually as an adjuvant to com-
mercial salting and pickling.
continuously and retail joints even more so. On the
other hand, evaporation is inhibited by membranes
such as the pleura and peritoneum and, in carcases of
well-nourished animals, by the solidification of the
superficial fat and drying of the connective tissue. A
freshly killed carcase dissipates body weight slowly,
losing 1.5-2.0% of weight by evaporation during the
first 24 hours of hanging. Further loss of weight during
storage depends on the humidity of the storage room:
the drier the air the greater the amount of evaporation.
The high-velocity cold air system (TurboChill) reduces
body heat of freshly killed animals by increasing the
rate of heat removal from the surface of the carcase and
hence reduces surface temperature quickly. Avoidance
of all evaporative weight losses by high humidity
facilitates the formation of moulds, so an accurate
balance between temperature and humidity must be
maintained; the dry, impervious film on the carcase
surface is perhaps the best protection against the
growth of spoilage organisms.
Sweating
This denotes the
condensation
of water vapour on meat
brought from a cold store into ordinary room tempera-
ture. The condensation occurs because the refrigerated
carcase lowers the temperature of the air to below the
dew point. In the winter months in Britain, the dew
point is generally below 4.5°C, and sweating is unlikely
to occur, but in the summer, the dew point is always over
7°C, and moisture will be deposited on the carcase. If
the quarter or side is cut up immediately after removal
from the chilling room, sweating will be extended to the
individual joints.
Physical changes in stored meat
Meat undergoes certain superficial changes as a result of
storage, chief of which are shrinkage, sweating and loss
of bloom.
Shrinkage
Shrinkage or loss of weight occurs as a result of
evaporation
of water from the meat surface; carcases
cut into quarters dissipate water vapour rapidly and
