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612 12 Meat

household as meat tenderizers. Analytical determination

of proteinases is relatively difficult.

A possible assay may be based on disc gel electrophoresis

of meat extracts, prepared in the presence

of urea and SDS. The band intensities of

the lower molecular weight collagen fragments

increase in proteinase-treated meat.

12.10.1.5 Anabolic Steroids

Anabolic compounds present in animal feed as

an additive increase muscle tissue growth. Owing

to a potential health hazard, some of these compounds

are banned in many countries. Their detection

can be achieved by the mouse uterus test

or by a radioimmunoassay. Special receptor proteins

which have the property of binding strongly

to estrogens are isolated from rabbit or cattle

uterus. The hormone-receptor complex is in equilibrium

with its components:

Receptor + estrogen ⇌ Receptor-estrogen

complex (12.30)

The nonlabelled estrogens bound to receptor in

the test sample will be competitively displaced

by the addition of 17-β-estradiol labelled with tritium

for radiochemical assay.

To reach equilibrium, a suitable amount of receptor

protein and a constant amount of labelled

estradiol are incubated together with the test sample.

The amount of the radioactive 3 H-estradiol

receptor complex will decrease in the presence

of competitive estrogens from the meat extract.

The binding affinity of the estrogen receptor depends

on the type of estrogen present (Fig. 12.42).

Hence, detection limits differ and range from 0.3

to 50 ppb (mg per metric ton).

Anabolic compounds can be further separated by

gas–liquid chromatography after derivatization

of the polar functional groups, and identified

by mass spectrometry. This method allows

the determination of weak or nonestrogenic

components too, but in the past it suffered from

high losses in sample preparation and could not

compete with radioimmunoassay in sensitivity.

In the meantime disadvantages of the method

have been eliminated.

12.10.1.6 Antibiotics

Antibiotics are used as part of therapy to treat animal

diseases and, sometimes in low concentrations,

as constitutents of animal feed to increase

feed utilization and to accelerate animal growth.

Detection of antibiotics is usually achieved by the

inhibition of the growth of bacteria (“inhibitor

test”). Bacillus subtilis, strain BGA, is one of the

recommended test organisms.

Chemical methods must be used in order to identify

and quantify the antibiotics and other veterinary

medical residues. The principal method

is chromatographic separation coupled with mass

spectrometry. The tetracyclines, which are common

antibiotics, can be determined relatively easily

by fluorometric measurement of adequately

prepared and purified meat extracts.

12.10.2 Processed Meats

Fig. 12.42. Relative binding affinity of estrogen compounds

to estrogen receptor. 50% binding achieved

by: 0.034 ng diethylstilbestrol (DES), 0.33 ng 17-βestradiol

(EST), 0.6 ng hexestrol (HEX), 1.2 ng zeranol

(ZER), 2.9 ng dienestrol (DIEN). (according to Ingerowski

and Stan, 1978)

Besides the estimation of the animal species and

the control of additives, the analysis of processed

meats is associated with verifying composition.

Here the emphasis is on the content of extraneous

added water, carbohydrate-containing thickeners

and binders, nonmeat protein additives and

fat. In addition, the determination of nitrites,

nitrates, nitrosamines and, for enhancing the

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