Food Chemistry

610 12 Meat

Fig. 12.39.Animal species with the same myoglobin patterns. Separation by isoelectric focusing of water soluble
muscle proteins [F], blood [B], and mixtures of both [F/B] (cf. Fig. 12.38, according toKaiser, 1988).aMyoglobin
and hemoglobin zones after treatment with o-dianisidine/H 2 O 2 ;bProtein zones after staining with coomassie
brilliant blue

impala, sheep, goat, and chamois. Here, the
hemoglobins can be used if the meat contains
sufficient blood components, as is usually the
case with game, or if blood is separately available
(Fig. 12.39a).
The analyses mentioned above are largely lim-
ited to raw meat because protein denaturation oc-
curs in heat treated meat. Denauration increases
with temperature and time and makes the im-
munochemical and electrophoretic identification
more and more difficult. Since DNA is more ther-
mostable than proteins, the PCR is a promising
alternative in these cases (cf. 2.6.4.2.2).
From the intensities of the indicator zones in an
electropherogram, it is possible to estimate the
proportion of one kind of meat in a meat mix.
This is illustrated in Fig. 12.40 using a mixture
of ground beef and pork.

12.10.1.1.2 Sexual Origin of Beef

The sexual origin of beef can be determined by

an analysis of the steroid hormones. Since the

concentrations of individual compounds vary too

greatly, the ratio of progesterone/pregnenolone

obtained from GC/MS is used. This value is

on average 0.5 for oxen and bulls and 7.9for

heifers.

12.10.1.2 Differentiation of Fresh

and Frozen Meat

The isoenzyme patterns of cell organelles, for in-

stance mitochondria and microsomes, differ of-

ten from those of cytoplasm. When the organelle

membranes are damaged by a physical or chem-