Composition and Nutritive value

Lesson 20 : Preparation and Processing of Meat

Composition and Nutritive value

Nutritive Value book - NIN

Table: Nutritive value of meat

Intracellular protoplasmic proteins : 83-90 % - These are involved in contraction of muscle.
Myosin : 60.0% - Protein of the thick filaments.
Actin : This is a major protein of thin filaments and constitutes
Tropomyosin : 15 – 30 per cent of myofibrils.
Troponin : This is found in thin filaments.
Muscle Protein : A component of contractile system.

Muscle protein consist of two types

  1. Intracellular or protoplasmic proteins and
  2. The structural proteins which are contributed by the connective tissues.

The protoplasmic proteins constitute 83 - 90 % of the total proteins, while the connective tissue proteins constitute about 10-17 % per cent of the total proteins. The chief protoplasmic proteins are myocin and actin. They are coagulated when heated. The chief connective tissue protein present in muscle is collagen. It is converted into gelatin during cooking of muscle.

  • Pigments: Myoglobin is the chief pigment responsible for the pink to red colour of muscle, although some red blood cells with their haemoglobin remain in the capillaries after the animal bled before slaughter. The amount of myoglobin in muscle varies with the age and breed of animal from 0.07 to 0.46 per cent the average myoglobin content being about 0.36 per cent.

  • Carbohydrates: The chief carbohydrate is glycogen which is present to the extent of about 1.0% per cent in resting muscle. The muscle taken from the slaughtered animal undergoes contraction ( rigor mortis) during which all the glycogen present undergoes glycolysis to lactic acid.

  • Protein: Meat contains 15-20 % protein of outstanding nutritive value. The lean meat contains 20 -22 % proteins. Biological value of meat protein is better than vegetable proteins. Fish protein has higher biological value than meat protein.

  • Water: Water is the largest single component of muscle by weight. Changes in the amount of water present and the extent to which it is bound by the muscle components is considered to influence the tenderness, texture and juiciness of meat, as well as the yield of cooked meat.

  • Fat: The fat content of meat varies from 5 to 40 per cent with the type, breed, and age of the animal. When the animal is well fed, fat deposits subcutaneously as a protective layer around the organ. Then it accumulates around and between the muscles. Finally, fat penetrates between the muscle fibre bundles and this is known as ‘marbling’. Marbling is desirable with some meat-like beef because the amount of fat and consequently the water- holding capacity of meat greatly influence juiciness.

    Meat fats are rich in saturated fatty acids. The cholesterol content of meat is about 75 mg per 100g. The lean portion of meat contains greater proportions of phospholipids (0.5 – 1.0) and these are located in the membrane of the cell. The fatty acids in the lean portion of meat have a higher proportion of unsaturated fatty acids than tissue fats.

  • Minerals: The mineral elements occur either as a variety of compounds within muscles. Calcium and magnesium are essential components of the contraction- relaxation cycle. Iron is a part of the red pigment and so influences colour. Zinc is found in one of the enzymes. Meat is a good source of iron and phosphorus. Meat also contains sodium and potassium. Liver is an excellent source of iron.

    Meat is an excellent source of some of the vitamins of the B complex. Liver is rich in vitamin B12 and vitamin A and iron.
    Meat contains protein hydrolyzing enzymes cathepsins and these are responsible for the increase in tenderness of meat during ageing.
    The colour of meat is primarily due to myoglobin and haemoglobin. Meats cured with nitrates remain pink as nitric oxide myoglobin is stable. Haemoglobin also contributes to the colour of meat to some extent.

    The flavour of meat has complex sensation, which is due to water soluble substances such as inosinic acid.

  • Proteolytic enzymes: The chief proteolytic enzyme present in meat is cathepsin. The optimum pH for its activity is 4.0. It is possible that cathepsin is involved in the development of tenderness in meat during ageing.
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Last modified: Monday, 12 December 2011, 11:11 AM