Meat skeletal muscles with natturally attached tissues

the term meat refers to muscles of warm blooded four legged animal

1. Meat The term meat refers to muscle of warm-blooded four-legged animals. Meat is defined as skeletal muscle with naturally attached tissue. The chief meat - cattle, sheep and pigs. Meat also includes the glands and organ of these animals. Meat product include many of the by-products from animal slaughter such as animal gut used for sausage casings, the fat in the manufacture of lard, gelatin and others.

2. Red meat consists of mutton, goat meat, pork, beef and rabbit meat. The redness of meat is due to myoglobin . The flesh of birds , fish, reptiles, amphibians, crustaceans and other sea food is not red meat. Salmon flesh and some lobsters look red but they do not come under the 'red meat' category. White meat is better compared to red meat for health reasons .

3. classes of meat and related products veal : It is the meat from cattle slaughtered 3 to 4 weeks after birth beef : Meat of cattle over 1 year old. mutton : Flesh of young ovine animal of both sexes whose age is 12 months or under yearling mutton : Carcasses of young sheep usually from 12 to about 20 months old are termed yearling mutton. mature mutton : Flesh of both the male and female of ovine species that are 20 month in age at a time of slaughter. pork : It is the meat of swine. Good quality pork is obtained from animals between the age of 3 -12 months before the amount of fat become excessive. organ meats : Liver, kidney, heart, thymus, pancreas and brain. sausages : Made of ground or minced meat and are enclosed in casings.

4. Composition and nutritive values proteins of muscle Myosin : 60 per cent protein of the thick filament Actin : This is a major protein of thin filaments and constitutes 15-30 per cent of myofibrils. Tropomyosin : This is found in thin filaments.

5. Troponin : A component of contractile system. Collages: It is abundant in tendons, skin. Bone. Vascular system of animals and connective tissue sheaths surrounding muscles. Collagen contributes to toughness and is partially denatured product. It increase with age and hence greater difficulty in chewing of meat of older animals than those from younger ones. Elastin : This is tougher than collagen and is a constituent of ligament. No change occurs during heating and it does not matter as elastin quantity is low .

6. Water : water is largest single component of muscle by weight. Changes in the amount of water present in 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. Carbohydrates : These are found only in very small quantities in meat. The carbohydrates found in meat are glycogen and glucose

7. Protein : Meat contains 15-20 per cent protein of outstanding nutritive value. The lean meat contains 20-22 per cent proteins. The total nitrogen content of meat, 9 5 per cent is protein and 5 per cent is the smaller peptides and amino acids. The amino acids made up of meat protein is very good for the maintenance and growth of human tissue. Biological value of meat protein is better than vegetable proteins. Fish protein have higher biological value than meat protein.

8. Fat : The fat content of meat varies from 5 to 40 % with a type, breed and age of the animals. When the animal is well fed, fat deposits as a protective layer around the organs. Then it accumulates around and between the muscles. Finally, fat penetrates between the muscle fiber 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 influences juiciness.

9. Meat fat are rich in saturated fatty acids. The cholesterol content is about 70 mg per 100 g. The lean portion of meat contains greater proportion of phospholipids (0.5-1.0 per cent) and these are located in the membrane of the cell. The fatty acid in the lean portion of meat have a higher proportion of unsaturated fatty acids than tissue fats. Lean meat is healthy.

10. Minerals : The mineral element occur either as separate ions or in a variety of compounds within muscles. Calcium and magnesium are essential components of the contraction – relaxation cycle. Iron is a part of red pigment and so influences colour , zinc is found in one of the enzymes. Meat is good source of iron and phosphorus. Meat also contain sodium and potassium. Liver is an excellent source of iron. Enzymes : Meat contains protein- hydrolyzing enzymes cathepsins and these are responsible for the increase in tenderness of meat during ageing.

11. Pigments : The colour of meat is primarily due to myoglobin and hemoglobin. Meats cured with nitrates remain pink as nitric oxide myoglobin is stable. Hemoglobin also contributes to the colour of meat to some extent. Flavour compounds : The flavour of meat is a complex sensation . Much of it is due to water-soluble substances such as inosinic acid, hypoxanthine derived from ATP, glycopeptides and amino acids such as glutamic acid. Meat with very little fat tastes insipid.

12. Post mortem changes Just before an animal is slaughtered, the muscles are soft and pliable. But immediately upon death, as metabolism in the cell interrupted processes being that lead to a stiffing of the carcass known as rigor mortis . I t is 24-48 hours in beef. Muscle is highly specialized tissue. It converts chemical energy for activity, ATP is derived by the carbohydrates and lipids.

13. When a muscle is under heavy stress and the oxygen is available is not sufficient, the anaerobic glycolysis system becomes predominant. Due to glycolysis in the post – mortem muscle, there is an accumulation of certain waste products especially lactic acid. Also the ATP concentration decrease and is lost in 24 hours or less. The increase in lactic acid concentration result in decrease in pH of post – mortem muscle.

14. Also in the absence of ATP, there is a formation of permanent links between actin and myosin, that is, the actin and myosin permanently fixed. The muscle passes into a state known as rigor mortis (stiffness of death). This post - -mortem effects brings about changes in the quality attributes of meat , such as texture and water – holding capacity , colour and flavour . Nutritional quality is not

15. Tenderising Tenderness is the most desirable characteristic in meat. The amount of distribution of connective tissues and the size of the both muscle fiber and boundless of fiber determine the tenderness of meat. The number and strength of cross linkage between the peptide chains of collagen increase with the age of the animal and this decreases the amount of collagen that may be solubilised during cooking thus contributing to decrease tenderness. There are different methods of tenderising meat.

16. Cold – room storage results in the ripening of meat with tenderising from the natural enzymes of meat. The mechanical method of tenderising of meat include pounding, cutting, grinding, needling or pinning and the use of ultrasonic vibrations. Mechanical methods cut or break the muscle fiber and connective tissues. The art of using enzymes for tenderising meat is an old one. Wrapping of meat in papaya leaves before cooking result in tenderisation . This is the result of action of enzymes papin on meat proteins. Other enzymes used for meat tenderisation are bromelain from pineapple.

17. In glycolysis , glycogen is converted into pyruvate and this is then reduced to lactate. Under usual conditions, lactate enters the liver, where it is converted into glucose. The glucose is then carried back to muscle, where eventually glycogen is resynthesised . When the animals dies the circulatory system ceases to work resulting lack of oxygen.

18. Meat can be tenderized by the use of low level salts . salts increase the water holding capacity of muscle fiber resulting in tenderness and juiciness . salt also solublilises the meat protein. Another method of increasing tenderness in meat is by change of pH. Decreasing or increasing the pH of meat increases hydration and to its tenderness .soaking beef for 48 hours in concentrated vinegar increases its tenderness and juiciness. Exercised animals give tender meat.

19. Changes during meat cookery Cooking destroys the micro-organisms that may have contaminated meat. Live trichinae are quickly destroy by heating the meat to 55°C. Cooking brings about changes in the colour of meat. When fresh meat is cooked its protein pigments are denatured. Denaturation of the protein causes rapid release of the haem pigment from the globin part of molecule and the free haem is very sensitive to oxidation. On heating , red meat generally turns brown due to the oxidised pigments in meat. This change in colour is used as an index of cooked meat.

20. Meat cooked to rare condition has less of oxymyoglobin denatured and more brown. Meats cured with nitrite retain red throughout cooking Heat treatment brings about the denaturation of most other proteins. The enzymes are inactivated. The contractile proteins become tougher. ideal cooking methods for meat should minimise the hardening of contractile protein and maximise the softening of the connective tissues. Cooking temperature and time should be adjusted so that the tenderising effect due to conversion of collagen to gelatin is not offset by the increasing toughness owing to an excessive coagulation of contractile protein.

21. Flavour compounds are produced or changed on heating. Proteins and free acids of meat on heating produce some volatile breakdown products. These include sulphur containing compounds, aldehydes , ketones , alcohols, amines and others. Lipid components also breakdown into various volatile compounds. These volatile compounds in both fat and lean portions of meat contribute to the flavour and odour of the cooked meat. Some 5 – nucleotides ( inosinic acid and guanylic acid ) are used in meat and poultry products as flavour potentiators .

22. During heating, meat fat melts, adipose tissue cells are ruptured and there is a redistribution of fat. Some fat is disposed finely in locations where collagen has been hydrolysed . When meat is eaten warm, the melted fat serves to increase the palatability of the product by giving a desirable mouth feel. Meat contains a high percentage of water. Only a small percentage of this water is bound very closely to the proteins, muscle tissues and the rest exists as free molecules within the muscle fibres and connective tissues. Heating reduces the water holding power of meat which is related to its juiciness. The loss of water on cooking does not bring about changes in the nutritive value of proteins.

23. Nutritive value of cooked meat generally remain high. Normal cooking does not bring about changes in the nutritive value of proteins and minerals are not lost by heat. Some minerals may be lost in meat drippings but on the other hand, cooking dissolves some calcium from bone and so enriches the meat in this mineral. There is loss of some B vitamins during cooking. But most of the cooked meats retain more than 50 per cent of the B vitamins present in the uncooked meats. Liver trichinal are quickly destroyed by heating the meat to 55°C.

24. Fish India has a cost line of 5, 100 km. Over 200 varieties of fish are known commercially important. Marine types are sardines, markerel , tuna, catfish, scombroides , brown duck, ribbon fish, prawns and cuttle . Carps, catla , rohu , mrigal , murrels and hilsa are the main catch from inland water. In india bulk of the fish is old in fresh (65-70 per cent) and dried (10-15 per cent) condition with very little processing and value addition.

25. Although fish contains complete proteins and can be alternative for meat in the diet, fish consumption per capita is far lower than that of meat. Shellfish are highly perishable. They are best when purchased directly from the fisherman. They may be expensive at shops in inland areas because of their very short storage life. The consumption and demand for shellfish, especially shrimps and prawns, has increased since frozen products become widely available. Crustacea have legs with partly jointed outer shells. They include crabs, lobsters, prawns and shrimps.

26. The dense coarse fish is found mainly in the claws and tail, eg . In the lobster and crab. This flesh is not as digestible as other type of fish. Lobesters and crab are best kept alive upto the point of their cooking or freezing, otherwise they deteriorate in quality in a matter o a day or less. Moulluscs have harder outer shell and no legs. They have hinged shells like oysters, scallops and muscles. Others have shells in one piece like snails, cockles and winkles.

27. Composition and nutritive value Commonly consumed fish are carp, rohu , sardine, mackerel pomfrets seer fish, prawns, ribbon fish sole, bombay duck, catfish and crab. Fish are not good source of energy because they are not good source of carbohydrates and fat. Carbohydrates : The shell fish has less fat and more carbohydrates than fin fish. Like meat, fish contain some glycogen in muscle tissues. In the live fish, glycogen is the source of stored energy. Oysters are notable for their high content of glycogen, on an average of 2-3 per cent.

28. Protein : Fish is an excellent source of protein due to its quality and quantity. They contain around 20 per cent protein. The biological value of fish protein is 80. Fish is rich in lysine and methionin hence it has supplementry value with cereals and pulses.

29. Fat : fish contains less amount of fat compared to meat and poultry. The lipid content of both fish and prawns is very low and varies within a very narrow range of 1-2,8 per cent. Crab small contains nearly 10 per cent fat. Vanjaram contains 4 per cent fat. Fish contains saturated fatty acids (40 per cent) monosaturated fatty acids (25 per cent) polysaturated fatty acid (ώ-3-25 per cent, ώ-6-10 per cent) fresh water fish contains eicosapentaenoic acid and decosahexaenoic acid which are ώ-3 polyunsaturated fatty acids.

30. Ώ-3 fatty acids content of some fish is given in white fish, any fat present in the fish is stored in the liver. Only minutes traces are found in the flesh. Most of the white fish are sea-water fish and live and the seabed. In oily fish, fat is distributed thought the flesh in the muscle fibres . The amount of fat may vary from 8 per cent to 15 per cent.

31. Fish cookery Principles of cooking fish : The changes that take place during the cooking of fish are smiliar to those in cooking meat. The main difference is that there is very little change in the colour of the fish. Since fish has little connective tissue and muscle fibres are short, it requires a much shorter cooking time than meat and poultry. All the connective tissue present in collagen which is converted to soluble gelatine by cooking.

32. Fish should be cooked at moderate temperatures long enough for its delicate flavour to develop, for protein to coagulate and for the small amount of connective tissues present to breakdown. The coagulation begins at a temperature of about 60°C. The flesh of fish is sufficiently cooked when it falls easily into clamps of snowy white flakes when tested with a fork. Cooking fish at a high temperature or cooking it too long, cause the muscle protein to shrink leaving the fish tough, dry and lacking in flavour . Fish can also be cooked by coagulating proteins with acids such as lemon or lime juice.

33. Spoilage Fish is considered in prime condition for up to three hours from catch, in average condition from three to six hours and on the way to spoilage from the sixth hour. While live fish is bacteriologically sterile, there are large number of bacteria on the surface slime and digestive tracts of living fish. When fish is killed, these bacteria multiply rapidly and attack all tissues. Since the bacteria live on the cold-blooded fish at rather low ocean temperatures, they are adapted to cold and continue to grow even under refrigerator conditions. Growth of micro-organisms and enzymes affect the quality.

34. Physical spoilage Fish struggles when caught and hence all the glycogen stores in the muscle and liver are used up. There is no glycogen left for being converted into lactic acid which helps to increase the pH of the tissues and retard the multiplication of micro-organisms.

35. Biological changes The important biochemical change leading to the development of characteristic fishy off odour is due to the production of trimethylamine by the action of bacterial enzymes on phospolipids and choline present in fish. The fat present in fish are highly unsaturated . By the action of bacterial lipase and lipodases , free fatty acids are produced and the fat undergoes oxidative rancidity. This result in additional oxidized and rancid off- flavours .