Meat composition

For Meat processing

1. TECHNOLOGY OF MEAT, POULTRY AND FISH PROCESSING UNIT I Meat composition from different sources; muscle structure and compositions; post-mortem muscle chemistry ; meat colour and flavours ; meat microbiology and safety. UNIT II Modern abattoirs, typical layout and features, abattoir equipment and utilities, ante-mortem handling and design of handling facilities ; hoisting rail and traveling pulley system; stunning methods; steps in slaughtering and dressing ; offal handling and inspection; inedible by-products; operational factors affecting meat quality ; effects of processing on meat tenderization. UNIT III Chilling and freezing of carcass and meat; canning, cooking, drying, pickling, curing and smoking ; prepared meat products like salami, kebabs, sausages, sliced, minced, corned; intermediate moisture and dried meat products; meat plant hygiene – GMP and HACCP. Packaging of meat products

2. TECHNOLOGY OF MEAT, POULTRY AND FISH PROCESSING UNIT IV Poultry industry in India, measuring the yields and quality characteristics of poultry products , microbiology of poultry meat, spoilage factors; lay-out and design of poultry processing plants , plant sanitation; poultry meat processing operations, equipment used – defeathering , bleeding , scalding etc.; packaging of poultry products, refrigerated storage of poultry meat, by products – eggs , egg products, whole egg powder, egg yolk products, their manufacture, packaging and storage . UNIT V Commercially important marine products from India; product export and its sustenance; basic biochemistry and microbiology; preservation of postharvest fish freshness; transportation in refrigerated vehicles; deodorization of transport systems; design of refrigerated and insulated trucks; grading and preservation of shell fish; pickling and preparation of fish protein concentrate, fish oil and other by products.

3. Meat Meat consumption in developing countries has been continuously increasing Average annual per capita consumption 10 kg in the 1960s 26 kg in 2000 37 kg around the year 2030 (FAO projections) Global meat production 267 million tons (2006) 320 million tons (2016) India – 6.2 million tons (2014)

4. Sources of Meat Meat products are mainly derived from the domesticated animal species like sheep, goats, cattle , buffaloes , pigs and poultry. Beef - from cattle > 1 yr. of age Veal - calves ( 3 months. or younger) Pork - swine Mutton -mature sheep Lamb -young sheep (< 1 year) Chevon -goats (goat meat)

5. Meat Meat can be defined as “the muscle tissue of slaughter animals ”. The skeletal muscle is the principal muscle tissue in meat, although very little of smooth tissue is also present . The other important tissue used for further processing is fat . Other edible parts of the slaughtered animal and often used in further processing are the internal organs (liver, kidneys, lungs, tongue, heart, diaphragm , oesophagus , intestines) and other slaughter byproducts ( blood, soft tissues from feet, head).

6. Skeletal w Voluntary muscle; controlled consciously forms the bulk of meat Cardiac w Controls itself with assistance from the nervous and endocrine systems w Found only in the heart Smooth w Involuntary muscle; controlled unconsciously Found in the walls of blood vessels and internal organs Types of Muscles There are more than 300 muscles in the animal body. These muscles constitute about 35-60% of the carcass weight of meat animals

7. Skeletal Muscle Skeletal muscles are muscles which are attached to the skeleton. Approx. 40 % of animal body mass Skeletal muscles are mainly responsible for locomotion , and voluntary contraction and relaxation . skeletal muscles are directly attached to the bones, although some attach indirectly via ligament, cartilage, fascia and skin. Each muscle is surrounded by a sheath of connective tissue known as epimysium . From the inner surface of epimysium, a septum of connective tissue penetrates into muscle and surrounds the bundles of muscle fibres or fasciculi . This connective tissue is called perimysium . It contains major blood vessels and nerves. Each muscle fibre is surrounded by a connective tissue layer called endomysium Cross-section of a typical muscle depicting arrangement of connective tissues and muscle fibres

8. An individual muscle cell is called a muscle fiber . Muscle fibres are usually 10-100μ in diameter with conical or tapering ends and their length ranges from 1-40 mm A muscle fiber is enclosed by a plasma membrane called the sarcolemma. The cytoplasm of a muscle fiber is called a sarcoplasm. Within the sarcoplasm, the T-tubules allow transport of substances throughout the muscle fiber and the sarcoplasmic reticulum stores calcium. Structure of single muscle fibre

9. Chemical composition of muscle meat Muscle tissue contains approximately 75% water and 25% solids, of which 19% are proteins. Lipids constitute about 2.5 to 5% of muscle In general, meat is composed of water, fat, protein, minerals and a small proportion of carbohydrate. The most valuable component from the nutritional and processing point of view is protein. Protein contents and values define the quality of the raw meat material and its suitability for further processing.

10. Chemical composition of muscle meat Water This is the largest component comprising two third to three fourth of the muscle tissue. Due to polar behavior, water molecules are attached with the electrically charged groups of muscle proteins. About 40 % of the total water in muscle is so tightly bound that it is almost impossible to dislocate it.

11. Protein Muscle proteins have been broadly classified into three categories: i ) Myofibrillar proteins -- soluble in dilute salt solution ii ) Sarcoplasmic proteins -- soluble in water or very dilute salt solution. iii ) Stroma or connective tissue proteins – almost insoluble

12. Chemical composition of a typical animal muscle

13. Composition of different meat

14. The nutritional value of meat and meat products Protein The nutritional value of meat is essentially related to the content of high quality protein. High quality proteins are characterized by the content of essential amino acids which cannot be synthesized by our body but must be supplied through our food. The myofibrillar proteins are quantitatively the most important (some 65%) and are also qualitatively important as they have the highest biological value. Connective tissues contain mainly collagen, which has a low biological value. Elastin is completely indigestible. Collagen is digestible but is devoid of the essential amino acid tryptophan. Blood proteins have a high content of tryptophan but are nevertheless of a lower biological value than meat due to their deficiency of the essential amino acid isoleucine

15. Fats Animal fats are principally triglycerides. The fatty acid composition of the fatty tissues is very different in different locations. External fat (body fat) is much softer than the internal fat surrounding organs due to a higher content of unsaturated fat in the external parts. Meat and meat products are relatively good sources of unsaturated fatty acids ( linoleic , linolenic and arachidonic acid), which are physiologically and nutritionally important

16. Vitamins Meat and meat products are excellent sources of the B-complex vitamins. The daily requirement for humans of this rarely occurring vitamin is 1-1.5 mg. Plant foods have no vitamin B12, hence meat is a good source of this vitamin. Internal organs, especially liver and kidney generally contain an appreciable percentage of vitamin A, C, D, E and K. Most of the vitamins in meat are relatively stable during cooking or processing, although substantial amounts may be leached out in the drippings.

17. Minerals The mineral contents of meat include calcium, phosphorus, sodium, potassium, chlorine, magnesium with the level of each of these minerals above 0.1%, and trace elements such as iron, copper, zinc and many others. Blood, liver, kidney, other red organs and to a lesser extent lean meat, in particular beef are good sources of iron. Iron in meat has a higher bio-availability, better resorption and metabolism than iron in plant products

18. The red pigment that provides the characteristic colour of meat is called myoglobin. Similar to the blood pigment haemoglobin it transports oxygen in the tissues of the live animal. Oxygen is needed for the biochemical process that causes muscle contraction in the live animal. Specifically , the myoglobin is the oxygen reserve for the muscle cells or muscle fibres . The greater the myoglobin concentration, the more intense the colour of the muscle. This difference in myoglobin concentration is the reason why there is often one muscle group lighter or darker than another in the same carcass Meat Color

19. Meat colour Myoglobin concentration in muscles also differs among animal species. Beef has considerably more myoglobin than pork, veal or lamb, thus giving beef a more intense colour . The maturity of the animal also influences pigment intensity, with older animals having darker pigmentation. Myoglobin is denatured by prolonged exposure to air or by cooking

20. The water holding capacity The capacity of meat to retain its water during the application of physical forces (during cutting , grinding, filling, pressing, or heating) is known as water holding capacity (WHC). WHC of meat is one of the most important factors of meat quality both from the consumer and processor point of view. it contributes to the juiciness of cooked meat besides influencing the texture and colour Fresh meat with a good water holding capacity is less prone to shrinkage during storage Muscle proteins are capable of holding many water molecules to their surface. As the muscle tissue develops acidity (decrease of pH) the water holding capacity decreases. Water holding capacity varies greatly among the muscles of the body and among animal species. Beef has the greatest capacity to retain water, followed by pork, with poultry having the least.

21. Tenderness Meat tenderness plays an important role, where entire pieces of meat are cooked , fried or barbecued. Factors Responsible for Tenderness in Meat 1. Genetics: In Beef it has been noticed that 45% of observed variation in tenderness of cooked Beef is due to genetics /parents of the animal. 2 . Species & Age: Tenderness – Variations in tenderness is observed to a great extent in Beef followed by lamb & pork. Tenderness depends on age of the animal at the time of slaughter Beef – 20 month, Lamb – 8 month Pork – 5month The decrease in tenderness with increasing age is due to charging nature of collagen (gristle), connective tissue protein found in meat. Collagen becomes complex & stronger with advancing age

22. Tenderness In these cases some types of meat, in particular beef, have to undergo a certain ripening or ageing period before cooking and consumption in order to achieve the necessary tenderness. beef's natural enzymes break down the connective tissue in the muscle, which leads to more tender meat Ageing of meat

23. Taste and flavour The typical desirable taste and odor of meat is to a great extend the result of the formation of lactic acid (resulting from glycogen breakdown in the muscle tissue) and organic compounds like amino acids and di- and tripeptides broken down from the meat proteins . In particular the aged (“matured”) meat obtains its characteristic taste from the breakdown to such substances. The “meaty” taste can be further enhanced by adding monosodium glutamate (MSG) ( 0.05- 0.1 %), which can reinforce the meat taste of certain products.

24. Post mortem Muscle chemistry Glycolysis and pH Decline Immediately post-mortem the muscle contains a small amount of muscle specific carbohydrate, called glycogen In the live animal glycogen is the energy reserve for the muscles used as fuel for muscle contraction In life: Glycogen + O 2 CO2 + H2O + ATP (energy) After death: Glycogen CH3 CH(OH)COOH (lactic acid) Glycogen is broken down to lactic acid in the muscle meat after slaughtering. Aerobic conditions Anaerobic conditions

25. Post mortem Muscle chemistry Glycolysis and pH Decline The build up of lactic acid in the muscle produces an increase in its acidity, as measured by the pH. The pH of normal muscle at slaughter is about 7.0 In a normal animal, the ultimate pH (expressed as pH 24 = 24 hours after slaughter) falls to around pH 5.8-5.4. The drop in pH is a desirable features as a low pH slows down growth of microorganism, and enhances flavour , juiciness and colour of the meat. The typical taste and flavour of meat is only achieved after sufficient drop in pH down to 5.8 to 5.4.

26. Post mortem Muscle chemistry Glycolysis and pH Decline The degree of reduction of muscle pH after slaughter is related to the amount of glycogen present in the muscle . Animals are held at rest before slaughter to make sure that they are not stressed prior to slaughter, as stress causes them to burn up their glycogen reserves. Meat of animals, which had depleted their glycogen reserves before slaughtering (after stressful transport/handling in holding pens) will not have a sufficient fall in pH and will be highly prone to bacterial deterioration . Meat from stressed animals has a high pH, causing it to be dark in colour , firm in texture and dry in taste (known as DFD meat ). Sharp decline in postmortem pH may cause denaturation of muscle proteins. So, the muscles depict pale, soft and exudative condition ( PSE meat ) .

27. Post mortem Muscle chemistry Rigor Mortis It refers to stiffening of muscles after death. The phenomenon of rigor mortis resembles that of muscle contraction in a living animal muscle except that rigor mortis is irreversible under normal conditions. A particular level or concentration of ATP complexed with Mg++ is required for breaking the actomyosin bond and bringing the muscle to a relaxed state As the conc. of ATP drops, permanent actomyosin cross bridges begin to form and muscle gradually becomes less and less extensible under an externally applied force. When postmortem pH decline is very slow or very fast , the onset and completion of rigor mortis is rapid. The onset of rigor mortis is enhanced at ambient temperature above 20 C .

28. Post mortem Muscle chemistry Degradation due to Proteolytic Enzymes Several autolytic lysosomal enzymes called cathepsins which remain inactive in a living muscle tissue, are activated as the muscle pH declines. These enzymes initiate the degradation of muscle protein structure. In fact, catheptic enzymes are capable of breaking down even collagenous connective tissue of the muscle and cause tenderization of meat during aging.

29. Post mortem Muscle chemistry Loss of Protection from Invading Microorganisms During postmortem period, body defence mechanism stops operating and membrane properties are altered. So , during conversion to meat, muscle is quite susceptible to invading microorganisms. Except for low pH, most of the other postmortem changes favour bacterial growth. Hence, utmost handling precautions are necessary to prevent contamination of meat