2009_Book_FoodChemistry

12.6 Kinds of Meat, Storage, Processing 595
protein. The proteins can be processed further by
spray-drying into powdered plasma. Recovery of
liquid plasma is permitted only from the blood
of cattle (excluding calves) and hogs. Addition
of dried and liquid plasma to processed meats
is legal. Citrate and/or phosphate are used as
calcium-binding agents.
12.6.1.11 Glandular Products
Animal glands, such as the adrenal, pancreas,
pineal, mammary, ovary, pituitary and thyroid
glands, provide useful by-products for
pharmaceutical use. Some of these products
are adrenalin, cortisone, epinephrine, insulin,
progesterone, trypsin and thyroid gland extract.
12.6.2 Storage and Preservation Processes
Meat must be appropriately treated to allow storage.
12.6.2.1 Cooling
Refrigeration (cooling or freezing the meat) is
an important process for prolonged preservation
of fresh meat. Carcasses in the form of sides or
quarters are cooled. Cooling is performed slowly
(e. g., with a blast of air at 0.5m/s at4 ◦ C) or
quickly (e. g., stepwise for 3 h with a 3.5m/s
blast of air at −10 ◦ C, for 19 h with a blast of
air at 1.2m/s at2 ◦ C, and over 18 days with air
at 4 ◦ C). The shelf-life of meat at 0 ◦ Cis3to
6 weeks. Weight loss due to moisture evaporation
is low at high relative humidities, and decreases
as the water holding capacity increases.
If meat is cooled to cold storage temperatures
(<10 ◦ C) before rigor occurs, it shrinks and
becomes tough. This is due to the fact that at low
temperatures, binding of Ca 2⊕ by the sarcoplasmic
reticulum and mitochondria is reduced, the
Ca 2⊕ concentration in the intracellular space is
increased, inducing contraction (cf. 12.3.2.1.5).
To prevent this phenomenon, meat is kept
at 15–16 ◦ C for 16–24 h and cooled after rigor
has occurred. Electrical stimulation is also possible.
This process causes rigor by accelerating
glycolysis and a decline in pH. The same effect
is achieved by stunning the animals with CO 2 .
As long as the meat is stored in the cold in large
cuts, lipid oxidation is very slow. Only chopping
or mincing or warming of the muscle tissue
causes a high rate of peroxidation. Muscle disintegration
results in a low but significant release of
highly unsaturated membrane phospholipids and
Fe 2+ ions from myoglobin. This non-heme iron is
an effective catalyst of lipid peroxidation. Its concentration
increases during cooking, as shown for
beef in Table 12.18. Even after short cold storage
of heated meat and subsequent warming, a rancid
off-flavor may develop (warmed over flavor,
WOF) (cf. 12.6.2.6 and 12.9.4).
Curing prevents WOF. Myoglobin is stabilized by
nitrite, therefore, no additional non-heme iron is
formed during cooking (Table 12.18). In addition,
the MbNO formed has an antioxidative effect
(cf. 12.3.2.2.4). Lipid peroxidation does not
occur and new aroma substances are formed that
are characteristic of cured meat.
12.6.2.2 Freezing
The shelf life of meat is substantially lengthened
by freezing. Freezing can be performed in a single
step (direct freezing) or in a two step process
(initial cooling followed by freezing) using an air
Table 12.17. Loss of quality of frozen chicken from
producer to consumer a
Frozen Average Shelf- Quality Average Quality
food storage life loss (% storage loss
chain tempera- (day) per day) time (%)
ture ( ◦ C)
(day)
Producer −23 540 0.186 40 7.5
Transport −20 420 0.239 2 0.5
Wholesaler −22 520 0.196 190 37.1
Transport −16 370 0.370 1 0.4
Retailer −20 420 0.239 30 7.2
−14 b 210 0.476 3 1.4
Transport −7 60 1.67 0.17 0.3
Consumer −12 150 0.666 14 9.3
∑ 280 63.7
a For definition cf. Fig. 12.29.
b A temperature estimate for food storage on the surface
of open freezers.