Food Chemistry

592 12 Meat

Fig. 12.28.Swelling of meat as affected by ATP add-
ition. Beef muscle homogenate; pH 6.8; — 2 h post-
mortem, −−−4 days post-mortem (according to
Hamm, 1972)

is still warm and due to the presence of high
concentrations of ATP. After the onset of rigor
mortis ATP breaks down, the rigidity of the
tissue increases and the water holding capacity
starts to decrease (Fig. 12.27). Addition of ATP
to muscle tissue homogenates prior to the onset
of rigor mortis brings about a rise in tissue
swelling (Fig. 12.28). Addition of low levels of
ATP (to about 1× 10 −^3 molar) during post-rigor
brings about tissue contraction or shrinkage,
while higher levels of ATP cause tissue swelling
(Fig. 12.28). This influence on swelling, however,
is of short duration since, as ATP breaks down,
contraction and shrinkage take place. Neverthe-
less, these studies amply illustrate the softening
effect of ATP and, as already mentioned, the abil-
ity of ATP to dissociate actinmyosin complexes
(cf. 12.3.2.1.5 and 12.3.2.1.6). Thus, because of
high ATP levels and high pH, the slaughtered
muscle which is still warm has a high water
holding capacity, whereas post-rigor meat, with
low ATP and low pH, has a low water holding
capacity.

12.6 Kinds of Meat, Storage,

Processing

Modern slaughterhouses are higly automated.
After the delivered animals are stunned either
electrically, or by using a bolt apparatus, or
with CO 2 , they are bled. The blood (3–4% of

the live weight) can be processed into plasma

(60–70%) and blood concentrate (30–40%,

hemoglobin). The animal bodies are then passed

to skinning machines via scalding vats and

unhairing machines. Subsequently, the animals

are disemboweled, the red organs and the stom-

ach/intestine package are separated for further

processing. The animals sides are passed through

a shock tunnel (air temperature−4to− 10 ◦C,

1–2 h). They are stored in the cold until they are

cut up on conveyor belts. During processing,

accumulating fat is fed to the grease boiler. All

discarded materials and bones are processed

into meat and bone meal in carcass processing

plants. The waste water is treated using specific

processes.

12.6.1 Kinds of Meat, By-Products

12.6.1.1 Beef

The most important categories are:

• Young bull meat from full-grown animals (18–
  22 months, live weight>300 kg): fine fibered,
  well marbled.


• Cow meat from animals (>2 years) which
  have already calved: medium red to brown
  red, moderately fine to coarse fibered, yellow
  fat, marbled.


• Heifer meat from young, full-grown female
  animals (15 to 24 months) which have not
  calved: red, fine fibered, white fat.

The meat of bulls (>5 years) and oxen (2–3

years) is of little economic importance. The

average amount of waste from slaughterhouse

oxen is 40–55%; that from cows, 42–66%. Beef

carcasses are hung for 4–8 days before being cut

up for soup meat, and 10–14 days for roasts or

steaks.

12.6.1.2 Veal

Meat from young cattle (ca. 4 months) with

a body weight up to 150 kg when slaughtered.

Color: pale red. The meat aroma is weaker than

that of beef. The meat is hung for 8 days before

use.