Processing and preparation of meat products

FOOD SCIENCE AND PROCESSING 3 (2+1)
Lesson 21 : Processing and Preparation of Meat and Poultry

Processing and preparation of meat products

  1. Factors affect the cooking quality of meat
    • Types and treatment of live animal.
    • Slaughtering and carcass characteristics, the various muscles of the carcass.
    • The composition, structure and function of the muscles.
    • Post-mortem changes.
    • Cooking methods.
    • Processing treatments.

  2. hanges during Cooking: Meat is cooked to destroy any harmful micro-organisms present in it and to improve its palatability. The changes brought about in meat by cooking are:

    • Change in colour During cooking myoglobin is denatured by heat and converted into brown or dull red globin haemochromogen. The iron is in the ferrous state but the globin is denatured by heat. At the same time, some of the myoglobin is oxidised to metamyoglobin which has a brown colour. The iron is in ferric state in metamyoglobin. Hence, the cooked meat assumes a dull red to brown colour.

    • Shrinkage (contraction) in volume and weight
      Decreases in volume and weight of meat take place as a result of cooking. The temperature of cooking affects both the rate and extent of shrinkage. Beef (450g piece) cooked under pressure at 120 0 C lost weight to a greater extent than beef cooked in steam (at 100 0 C) for the same period.
      The pH of the meat seems to be most important factor in determining the loss in cooking. The shrinkage is greatest if the meat has a pH of 5.8, i.e., the isoelectric point of the main protein of muscle. The shrinkage is less at pH4.0 or 7.0.

    • Changes in fatty tissue
      The fat cells are enclosed in membranes chiefly of collagenous tissue. The membranes break during cooking and melted fat escapes from meat during cooking. The surface browning of fat may be due to oxidation of fat. The amount of fat found in the drip varies depending on the fat content of meat.

    • Changes in connective tissue
      The connective tissue contains about 62 percent water, 32 per cent collagen and 1.6 per cent elastin. Collagen is converted into soluble gelatine during cooking of meat. The gelatine gets dissolved in the water used for cooking. Elastin does not undergo any change during cooking.

    • Changes in intracellular proteins and muscle fibres
      The protoplasmic proteins found in muscle are denatured and become insoluble in water. The diameter and length of the muscle fibre shrink.

    • Flavour
      The odour and taste of cooked meat arise from water and fat-soluble substances present in raw meat and by the liberation of volatiles formed during cooking. Water extract of raw meat develops a meaty flavour on heating. Nucleotides (inosine-5 monophosphate) are substantially responsible for the flavour of meat during cooking.

    • Juiciness
      The degree of shrinkage on cooking is directly correlated with loss of juiciness depends on the ability of the meat proteins to retain the cooked water. The juiciness of cooked meat is greater at PH 4.0 or at PH 7.0 than at PH 5.8.

    • Gelatine
      When collagen is heated, some intermolecular and few main-chain peptide bonds are hydrolysed. This results in the conversion of the triple helical structure of collagen to a more amorphous form known as gelatin. Gelatin is a partially-degraded collagen.

      Gelatin forms a gel in water even at a concentration of one percent. Gelatin is used in canned foods, semi preserve, confectionery, marsh mellows, ice cream and gelatin dessert such as jellies.Gelatin is a protein of low biological value as it deficient in essential amino acids such as tryptophan, theronine, methionine and isoleucine.
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Last modified: Monday, 12 December 2011, 11:30 AM