Food Chemistry

12.10 Meat Analysis 611

Fig. 12.40.Blended beef and pork meat: Densitograms
of sarcoplasm proteins separated by PAGIF and PAG-
plate; pH range 3.5–9.5. B/P (beef/pork) blend ratios in
weight %. (according toKaiser, 1980b)

ical process, isoenzyme blending will occur in the
cytoplasm.
Such membrane damage has been observed by
freezing and thawing of tissue, for example, of
muscle tissue, in which the isoenzymes of glu-
tamate oxalacetate transaminase (GOT) bound to
mitochondrial membranes are partially released
and found in the sarcoplasm. The pressed sap
collected from fresh unfroze meat has only sar-
coplasm enzymes, while the frozen and thawed
meat has, in addition, the isoenzymes derived
from mitochondria. The GOT isoenzymes can be
separated by electrophoresis (Fig. 12.41). This
procedure is also applicable to fish.

Fig. 12.41.Differentiation of fresh liver (1) from frozen

and thawed liver (2) by electrophoretic separation

of glutamate-oxalacetate transaminases (a) GOT sar-

coplasm, (b) GOT mitochondria (according toHamm

andMaši ́c, 1975)

The enzymeβ-hydroxyacyl-CoA-dehydrogenase

(HADH, EC 1.1.1.35) is also suitable for the

detection of frozen meat or fish. In the oxidation

of fatty acids, HADH catalyzes the reaction

shown in Formula 12.29. This enzyme is bound

to the inner membrane of mitochondria and is

liberated in the freeze/thaw process. Its activity

can then be measured in the issuing sap with

acetoacetyl CoA or with the artificial substrate

N-acetylacetoacetylcysteamine.

3-Oxoacyl-CoA+NADH+H⊕→

(S)-3-Hydroxyacyl-CoA+NAD⊕ (12.29)

12.10.1.3 Pigments

Pigment analysis is carried out for the evaluation

of meat freshness. The individual pigments, such

as myoglobin (purple-red), oxymyoglobin (red)

and metmyoglobin (brown), are determined.

12.10.1.4 Treatment with Proteinase

Preparations

Proteinases injected intramuscularly or through

blood vessels degrade the structural proteins and,

hence, proteolytic enzymes can be used to soften

or tenderize meat. The enzymes are of plant or

microbial origin and are used in the meat and

poultry industries, while some are also used in the