Food Chemistry

612 12 Meat

household as meat tenderizers. Analytical deter-
mination of proteinases is relatively difficult.
A possible assay may be based on disc gel elec-
trophoresis of meat extracts, prepared in the pres-
ence 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 com-
pounds are banned in many countries. Their de-
tection can be achieved by the mouse uterus test
or by a radioimmunoassay. Special receptor pro-
teins which have the property of binding strongly
to estrogens are isolated from rabbit or cattle
uterus. The hormone-receptor complex is in equi-
librium with its components:

Receptor+estrogenReceptor-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 tri-
tium for radiochemical assay.
To reach equilibrium, a suitable amount of re-
ceptor protein and a constant amount of labelled

Fig. 12.42.Relative binding affinity of estrogen com-
pounds to estrogen receptor. 50% binding achieved
by: 0.034 ng diethylstilbestrol (DES), 0.33 ng 17-β-
estradiol (EST), 0.6 ng hexestrol (HEX), 1.2 ng zera-
nol (ZER), 2.9 ng dienestrol (DIEN). (according toIn-
gerowskiandStan, 1978)

estradiol are incubated together with the test sam-

ple. 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 de-

pends 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 ani-

mal diseases and, sometimes in low concentra-

tions, 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 iden-

tify and quantify the antibiotics and other vet-

erinary medical residues. The principal method

is chromatographic separation coupled with mass

spectrometry. The tetracyclines, which are com-

mon antibiotics, can be determined relatively eas-

ily by fluorometric measurement of adequately

prepared and purified meat extracts.

12.10.2 Processed Meats

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