Food Biochemistry and Food Processing

13 Biochemistry of Raw Meat and Poultry 295

gree of fatness, and dressing method: 35% for beef,

32% for veal, 36% for pork, 25% for lamb, 50% for

turkey, and 39% for broiler chicken. The muscle to

bone ratio is also an important parameter representa-

tive of muscling: 3.5 for beef, 2.1 for veal, 4.0 for

pork, 2.5 for lamb, 2.9 for turkey and 1.8 for poultry

(Kauffman 2001).

MUSCLE COMPOSITION

Essentially, meat is basically composed of water, pro-

teins,lipids,minerals,andcarbohydrates.Leanmuscle

tissue contains approximately 72–74% moisture, 20–

22 % protein, 3–5% fat, 1% ash, and 0.5% of carbo-

hydrate. An example of typical pork meat composi-

tion is shown in Table 13.1. These proportions are

largely variable, especially in the lipid content, which

depends on species, amount of fattening, inclusion of

the adipose tissue, and so on. There is an inverse rela-

tionship between the percentages of protein and

moisture and the percentage of fat so that meats with

high content of fat have lower content of moisture

and proteins. A brief description of proteins and lip-

ids as major components of meat is given below.

MUSCLEPROTEINS

Proteins constitute the major compounds in the mus-

cle, approximately 15–22%, and have important roles

for the structure, normal function, and integrity of the

muscle. Proteins experience important changes dur-

ing the conversion of muscle to meat that mainly

affect tenderness; and additional changes occur dur-

ing further processing, through the generation of

peptides and free amino acids as a result of the pro-

teolytic enzymatic chain. There are three main groups

of proteins in the muscle (see Table 13.2): myofibril-

lar proteins, sarcoplasmic proteins, and connective

tissue proteins.

Myofibrillar Proteins

These proteins are responsible for the basic myo-

fibrillar structure, and thus they contribute to the

Table 13.1.Example of the Approximate Composition of Pork Muscle Longissimus dorsi,

Expressed as Means and Standard Deviation (SD)

Units Mean SD

Gross composition
Moisture g/100g 74.5 0.5
Protein g/100g 21.4 2.1
Lipid g/100g 2.7 0.3
Carbohydrate g/100g 0.5 0.1
Ash g/100g 0.9 0.1

Proteins
Myofibrillar g/100g 9.5 0.8
Sarcoplasmic g/100g 9.1 0.6
Connective g/100g 3.0 0.4

Lipids
Phospholipids g/100g 0.586 0.040
Triglycerides g/100g 2.12 0.22
Free fatty acids g/100g 0.025 0.005

Some minor compounds
Cholesterol mg/100g 46.1 6.1
Haem content mg/100g 400 30
Dipeptides mg/100g 347.6 35.6
Free amino acids mg/100g 90.2 5.8
Sources:From Aristoy and Toldrá 1998; Hernández et al. 1998; Toldrá 1999, unpublished).