Food Chemistry

608 12 Meat

drolysate is used as the amino acid source and
other important precursors of meat aromas like
thiamine and monosaccharide phosphates are ap-
plied in the form of yeast autolysates.
Fats or oils are added to produce the carbonyl
compounds which contribute to the animal
species specific note of meat aroma.

12.9.4 Aroma Defects

If cooked meat is stored for a short time, e. g.,

48 h at ca. 4◦C, an aroma defect develops, which
becomes unpleasantly noticeable especially after
heating and is characterized by the terms metal-
lic, green, musty and pungent. This aroma defect,
also called warmed over flavor (WOF), is caused
by lipid peroxidation (cf. 12.6.2.1). The indicator
of this aroma defect is hexanal, which increases
as shown in Table 12.27.
Other changes which contribute to the aroma de-
fect are the increase in metallic/musty smelling
epoxydecenal, which, like hexanal, is formed in
the peroxidiation of linoleic acid (cf. 3.7.2.1.9),
and the decrease in HD3F. The latter is probably
due to the reaction of its enolic OH group with
peroxy radicals.
The WOF appears in chicken much faster
because its linoleic acid content is about 10 times
higher than that in beef. Apart from the changes
in concentration of the odorants listed in Ta-
ble 12.27, the degradation of 2,4-decadienal,
which is typical of an advanced lipid peroxidation

Table 12.27.Changes in the concentrations of import-
ant aroma substances on cold storage and reheating of
roasted beef

Concentration

(μg/kg)

Compound Ia IIb

Hexanal 269 2329
trans-4,5-Epoxy-(E)-2-decenal 1. 510. 7
4-Hydroxy-2,5-dimethyl-3(2H)
-furanone (HD3F) 1108 665

aI: hamburgers were fried for 7 min.
bII: as in I, then storage at 4◦C for 48 h and heated

at 70◦C for 45 min until a core temperature of 60–
65 ◦C is reached.

(cf. 3.7.2.1.9), has an additional negative effect

on the aroma.

The WOF is inhibited by additives which bind

Fe ions, e. g., polyphosphates, phytin, and EDTA.

In comparison, antioxidants are almost ineffec-

tive. Therefore, it is assumed that a site specific

mechanism is involved in the formation of WOF.

The Fe ions liberated in the cooking process are

bound by the phospholipids via the negatively

charged phosphate residues and, consequently,

adjoin the unsaturated acyl residues of these

lipids. Radicals from theFentonreaction of Fe

ions with hydroperoxides (cf. 3.7.2.1.8) attack

only the unsaturated acyl residues, starting their

peroxidation. This hypothesis can also explain

the observation that multivalent ions (Ca^3 ⊕,

Al^3 ⊕) inhibit WOF as they probably displace the

Fe ions from the phospholipids.

12.10 Meat Analysis

12.10.1 Meat

The determination of the kind of animal, the ori-

gin of meat, differentiation of fresh meat from

that kept frozen and then thawed, and the con-

trol of veterinary medicines is of interest. The lat-

ter include antibiotics (penicillin, streptomycin,

tetracyclines, etc.) used to treat dairy cattle in-

fected with mastitis, and other chemicals, includ-

ing diethyl stilbestrol, used for cattle to increase

the efficiency of conversion of feed into meat.

12.10.1.1 Animal Origin

The animal origin of the meat can be determined

by immunochemical and/or electrophoretic meth-

ods of analysis as well as by PCR. The PCR

method is described in 2.6.4.2.2. Electrophoretic

protein analysis will be discussed here. The sex-

ual origin of a meat sample can also be of interest,

as discussed here for beef.

12.10.1.1.1 Electrophoresis

To determine the animal or plant origin of the

food, electrophoretic procedures have often