Food Chemistry

12.10 Meat Analysis 613

pinkish-red color of processed meat,L-ascorbic
acid is of importance in pickle-cured meat
products. Other analytical problems involve the
detection of condensed phosphates, citric acid
and glucono-δ-lactone, as well as the detection
of polycyclic aromatic compounds in smoked
meats, of mycotoxins in products with desirable
or undesirable growth of molds and of chlorine
compounds in seasonings.

12.10.2.1 Main Ingredients

The first insight into the composition of processed
meat, i. e. whether it contains an excess of fat or
carbohydrate, which would lower the protein con-
tent and thus lower the value of the processed
meat, is obtained by proximate analysis of the
product’s main ingredients: moisture, raw pro-
tein, fat and ash content. If their sum is less than
100 ± 0 .5% of the sample weight, then the pres-
ence of carbohydrate binders should be verified.
A positive finding should be further investigated
since incorporation of liver into processed meat
may provide glycogen. Hence, thorough carbohy-
drate analysis is required.

12.10.2.2 Added Water

Moisture content is related to protein content and
is relatively constant.Feder’smethod of analy-
sis of water added to chopped or ground meat or
to emulsion-type sausages is based on these find-
ings. The method uses the empirical equation:

Water added(%)=Moisture(%)

−Protein(%)×F (12.31)

F for beef and pork= 4 .0;

F for poultry leg= 3 .9 and breast= 3. 6

This indirect method for assessing the amount
of added water has been repeatedly criticized.
In spite of this, no better method has yet been
developed. Moreover, the calculated water con-
tent is never used alone to evaluate a meat prod-
uct. Other significant data, such as muscle protein
content and the proportion of fat to protein, are
also included.

12.10.2.3 Lean Meat Free of Connective

Tissue

A measure of meat quality is expressed as the

amount of lean meat free of connective tissue,

which corresponds to meat proteins devoid of

connective tissue protein (MPDCP). To obtain

this value, the meat sample is analyzed for

connective tissue proteins (CP), added extra-

neous protein (EP) and nonprotein-nitrogen

(NPN), e. g., glutamate, purine and pyrimidine

derivatives, urea. These values are then deducted

from the value for total protein (TP):

MPDPC=TP−(CP+EP+NPN) (12.32)

Another method still being tested is based on

drastic treatment (heating to 130◦CatpH9)of

a meat sample. Under these conditions, extrane-

ous proteins, collagen and blood plasma proteins

solubilize, while the residual protein is calculated

as MPDCP using a constant factor.

12.10.2.3.1 Connective Tissue Protein

The amino acid 4-hydroxyproline is a marker

compound for connective tissue. It occurs only

in connective tissue protein. The amount of

4-hydroxyproline is determined in the acidhy-

drolysate of the sample or the isolated protein

using an amino acid analyzer, or color-imetrically

using a specific color reaction. The latter, ac-

cepted widely in practice, is a direct photometric

procedure based on the oxidation of hydroxypro-

line in alkaline solution by H 2 O 2 or N-chloro-

p-toluenesulfonamide (chloramine-T). The oxi-

dation yields a pyrrole derivative which is then

condensed with p-dimethylaminobenzaldehyde

to form a red pigment. The connective tissue

content of meat is calculated by multiplying the

hydroxyproline value by a factor of 8, which cor-

responds to an average of 12.4% hydroxyproline

content of connective tissue.

12.10.2.3.2 Added Protein

In order to extend or improve the water hold-

ing capacity of processed meat, the product may