2009_Book_FoodChemistry

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 to Kaiser, 1988). a Myoglobin
and hemoglobin zones after treatment with o-dianisidine/H 2 O 2 ; b Protein 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 limited
to raw meat because protein denaturation occurs
in heat treated meat. Denauration increases
with temperature and time and makes the immunochemical
and electrophoretic identification
more and more difficult. Since DNA is more thermostable
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 7.9 for
heifers.
12.10.1.2 Differentiation of Fresh
and Frozen Meat
The isoenzyme patterns of cell organelles, for instance
mitochondria and microsomes, differ often
from those of cytoplasm. When the organelle
membranes are damaged by a physical or chem-