2009_Book_FoodChemistry

12.10 Meat Analysis 611
Fig. 12.41. Differentiation of fresh liver (1) from frozen
and thawed liver (2) by electrophoretic separation
of glutamate-oxalacetate transaminases (a) GOT sarcoplasm,
(b) GOT mitochondria (according to Hamm
and Mašić, 1975)
The enzyme β-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)
Fig. 12.40. Blended beef and pork meat: Densitograms
of sarcoplasm proteins separated by PAGIF and PAGplate;
pH range 3.5–9.5. B/P (beef/pork) blend ratios in
weight %. (according to Kaiser, 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 glutamate
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 sarcoplasm
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.
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