Meat Dr Fatimah Yousef Nutrient content of meat

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+ Meat Dr. Fatimah Yousef

+ Meat Dr. Fatimah Yousef

+ Nutrient content of meat Meat consists of water, protein, and fat, with a

+ Nutrient content of meat Meat consists of water, protein, and fat, with a few minerals (iron, zinc, copper, phosphours and a few trace minerals) and some B-vitamins (B 2, B 6, B 12 and niacin and some folate). Trace amount of carbohydrate, no fiber and no vitamin C. Water: It about 75% of the total weight, it is an important elements that affect the softer tissues also affect the color and taste. Protein: Meat serves as an important source of high-quality protein. Fat: It content vary widely according to the grade of meat and its cut.

+ Types of meats n. Cattle are classified according to age and gender. n.

+ Types of meats n. Cattle are classified according to age and gender. n. Steers: Most of the consumed beef is supplied by steers, male cattle that have been castrated while young so that they will gain weight quickly. n. Cows: Are female cattle that have born calves Dr. Fatimah Yosef 1, 2013

+ n Veal: Types of meats Comes from calves of beef cattle, either male

+ n Veal: Types of meats Comes from calves of beef cattle, either male or female, between the ages of three weeks and three months. The meat of these very young animal have pale color and tender texture. Calves three to eight month sold are too old for veal and too young for beef. Dr. Fatimah Yosef 1, 2013

+ Types of meats Lamb and Mutton: n Lamb comes from sheep less than

+ Types of meats Lamb and Mutton: n Lamb comes from sheep less than fourteen months old. n Mutton from those over fourteen months. is darker and tougher than and has a stronger flavor. The animal’s age, diet, and species affect the color and texture of fat. Dr. Fatimah Yosef 1, 2013

+ Composition of meats Structure of Meat: n Meats are composed of a combination

+ Composition of meats Structure of Meat: n Meats are composed of a combination of: n Water. n Muscle. n Connective tissue. n Adipose (fatty) tissue. n Bone. The proportions of these elements vary according to: the animal, and the part of its anatomy represented by the cut of meat. Dr. Fatimah Yosef 1, 2013

+ Composition of meats Muscle tissues: n Most of the protein in animals is

+ Composition of meats Muscle tissues: n Most of the protein in animals is found in their muscles, which serve as the main sources of dietary meat. n They are an important consideration in deciding how the resulting meat should be prepared.

+ Muscle contraction and relaxation n Muscle fibrils play an important role in muscle

+ Muscle contraction and relaxation n Muscle fibrils play an important role in muscle contraction and relaxation. n It is separated into segments called sarcomeres, which contain two protein actin (thin) and myosin (thick). n Muscle contraction occurs when the sarcomeres shorten as the thick and thin filaments “slide” past each other, forming another protein called actinomyosin. n The energy for muscle contraction is provided by (ATP).

+ Composition of meats Connective tissue: n It is a part of ligaments and

+ Composition of meats Connective tissue: n It is a part of ligaments and tendons, and it also acts as the “glue” that holds muscle cells together. n It is composed primarily of a mixture of proteins and mucopolysaccharides. n The most abundant protein is collagen**, which it is: Pearly white, tough, and fibrous protein that provides support to muscle and prevents it from over-stretching. It consists of three collagen strands twisted together.

+ n The other two proteins in connective tissue are: Elastin and reticulin, they

+ n The other two proteins in connective tissue are: Elastin and reticulin, they have less effect on meats when they are cooked. n Elastin: Yellowish, rubbery, has elastic quality and often referred to as “sliver skin”. It does not soften with heating, so it should be removed before preparation. There is very little in meats , expect in cuts from the neck and shoulder, it is less likely to affect tenderness n Reticulin consists of very small fibers of connective tissue that form a delicate interlace around muscle cells.

+ Elastin: “sliver skin”. It does not soften with heating, so it should be

+ Elastin: “sliver skin”. It does not soften with heating, so it should be removed before preparation.

Composition of meats + Adipose (fatty )tissues: n It serves as insulation under the

Composition of meats + Adipose (fatty )tissues: n It serves as insulation under the skin and as padding in the abdominal cavity for sensitive internal organs. n The outside fat in meat called cover fat, which help retain the moisture of meats, but this separable fat is often trimmed off meats prior to preparation. n Fat found within muscles called marbling. content, color and texture varies widely among meats and is dependent on the source animal's genetics, age , diet and exercise, and on the cut of the meat.

+ Why is marbling desirable in meat? n When meat is cooked, the intramuscular

+ Why is marbling desirable in meat? n When meat is cooked, the intramuscular fat deposits melt and contribute to perceived flavor and juiciness. For this reason, the more marbling in a cut of beef, the higher the grade. n Marbling: Fat deposited in the muscle that can be seen as little white streaks or drops.

+ Bone: Composition of meats n Bone are used as landmarks for identifying the

+ Bone: Composition of meats n Bone are used as landmarks for identifying the various meat cuts from a carcass. Meat pigments n The color of meat is derived from pigment-containing proteins. n Myoglobin and to a lesser extent hemoglobin. n The higher the concentration of myoglobin in raw meat, the more intense its bright red color.

+ n Meat pigments color varies from species to species, beef is darker than

+ n Meat pigments color varies from species to species, beef is darker than lamb. n Heavily exercised muscle has a higher demand for oxygen, so it is higher in myoglobin and therefore redder than less exercised muscles.

+ Effect of oxygen on color: n Exposure of meat to oxygen changes the

+ Effect of oxygen on color: n Exposure of meat to oxygen changes the color of myoglobin and therefore the meat color. n After cutting, meat undergoes several changes in color over time that are due to modifications in the molecular structure of myoglobin and/or hemoglobin. n Myoglobin within the meat is purplish red (myoglobin). n As soon as meat is cut and exposed to oxygen in the air, the bright red compound (oxymyoglobin) forms a color indicating freshness and desired by consumers.

+ n. Over time meat left and exposed to less oxygen and light all

+ n. Over time meat left and exposed to less oxygen and light all of which turn the bright red oxymyoglobin is oxidized to (metmyoglobin), which is a brownish-red color. n. Older meat cuts look browner because myoglobin or oxymyoglobin is converted to metamyoglobin as the iron in the pigment is oxidized from its ferrous (Fe +2) to ferric (Fe+3) state. This usually occurs during storage long time. The brownish-red color resulting from metamyoglobin is undesirable.

+ Color change in meat + oxygen (oxidized) Myoglobin -oxygen (reduced ) d) ze

+ Color change in meat + oxygen (oxidized) Myoglobin -oxygen (reduced ) d) ze d ce yg (re du d) ce d du e r ox en ze + yg idi di ox -ox xi en ( (o yg (Bright red) Fe+2 en (Purplish red) Fe+2 + ox Oxymyoglobin ) Metmyoglobin (Brownish-red) Fe+3 - en g y ox ( )

+ Why does a carcass stiffen? n **Rigor mortis is caused by a cascade

+ Why does a carcass stiffen? n **Rigor mortis is caused by a cascade of events that take place at the cellular level. Death interrupts the blood flow and prevents oxygen from reaching the cells. Changes then occur within the cells of the muscles, causing them to contract and stiffen. n The rigidity of the muscles in rigor mortis occurs because the crosslinks between the actin and myosin filaments overlap and cause the sarcomeres to shorten. The automatic contraction of fibrils in the muscle cells causes the characteristic muscle stuffiness. **Rigor mortis: From the Latin for “stiffness of death, ” the temporary stiff state following death as muscles contract.

+ Aging n Aging: Ripening that occurs when carcasses are hung in refrigeration units

+ Aging n Aging: Ripening that occurs when carcasses are hung in refrigeration units for longer periods than that required for the reversal of rigor mortis. n Aging meats improves their juiciness, tenderness, flavor, color and their ability to brown during heating.

Purchasing meats n It is important to ensure that consumers are purchasing meat that

Purchasing meats n It is important to ensure that consumers are purchasing meat that is safe. n Yield grade: The amount of lean meat on the carcass in proportion to fat, bone, and other inedible parts. Dr. Fatimah Yosef 1, 2013

+ Cuts of meats : n There are two major types of meat cuts,

+ Cuts of meats : n There are two major types of meat cuts, wholesale and retail. n Prior to reaching the supermarket, a carcass is divided into about seven wholesale or primal cuts. n Wholesale (primal) cuts: The large cuts of an animal carcass, which are further divided into retail cuts. n These wholesale cuts are then divided into the retail cuts purchased by consumers. n Retail cuts: Smaller cuts of meat obtained from wholesale cuts and sold to the consumer. Dr. Fatimah Yosef 1, 2013

+ n The Effect of age on composition of animals percentage of water: It

+ n The Effect of age on composition of animals percentage of water: It decrease in the animal's body in advanced aged. n Fat: Fat content, color and texture varies widely among. It is white in younger animal, and turns progressively more yellow as the animal age because of carotenoid pigments in the feed. Including more polyunsaturated fatty acids in the animal's diet make its fat softer. n Meat pigments: The red color of meat increases as the animal ages. n Older meat is less tender for two reasons: The collagen content of meat increases with an animal's age.

+ n Extractives: Extractives Flavor compounds consisting of non-protein, nitrogen substances that are end-products

+ n Extractives: Extractives Flavor compounds consisting of non-protein, nitrogen substances that are end-products of protein metabolism. n The meat from older animals contains more connective tissue and extractives and therefore yield more flavor than that from younger. n Extractives are water soluble so some of the flavor of boiled or simmered beef may be lost in the cooking water. n The flavor can be recaptured by using the cooking liquids in the preparation of soup.

Tenderness of meats + Natural tenderizing n The particular cut of the meat. n

Tenderness of meats + Natural tenderizing n The particular cut of the meat. n Age at slaughter (connective tissue concentration). n Heredity and diet. n Marbling. n Slaughtering conditions. n Aging. …all play a part in determining tenderness Dr. Fatimah Yosef 1, 2013

+ n The Effect of collagen on tenderness amount and type of connective tissue

+ n The Effect of collagen on tenderness amount and type of connective tissue found in a meat cut determines its tenderness or toughness and the best type of cooking methods. n Cuts high in connective tissue are tough and need to be properly heated in order to become more tender, such as those found in neck, shoulders, legs and flank, contain more collagen and tend to be tougher than muscles from loin, or lower back and rib areas which get less exercise.

+ n Tougher cuts require slow, moist heating at low temperatures to convert, or

+ n Tougher cuts require slow, moist heating at low temperatures to convert, or hydrolyze the tough connective tissue to softer gelatin. n On the other hand, the tougher cuts have more flavor than the tender ones.

+Artificial tenderizing : External treatments can be applied to meats to increase their tenderness.

+Artificial tenderizing : External treatments can be applied to meats to increase their tenderness. These include the use of : n Enzymes n Salts. n Acids n Mechanical methods such as grinding and pounding.

+ Artificial tenderizing: 1 - Enzymes: n Commercial meat tenderizers containing enzymes are available

+ Artificial tenderizing: 1 - Enzymes: n Commercial meat tenderizers containing enzymes are available for consumer to use. n Tenderizers are sold as a salt or liquid mixture and differ in the proteolytic enzymes. n The most common enzymes used: Papain from papayas, Bromelin from pineapples and Ficin from figs. n They are effective only on fairly thin cuts of meat because they penetrate to a depth of only 2 millimeters. n They are ineffective on larger cuts.

+ n The enzymes are not active at room temperature. The optimal activity temperature

+ n The enzymes are not active at room temperature. The optimal activity temperature for papain, the most common tenderizing enzyme is about (55 -76 °C), which is reached only during heating, exceeding temp. denatures the enzyme, thus inhibiting its activity. n Excessive amount of enzyme can cause the meat to have an unappetizing mealy and mushy texture. .

+ n. A more even distribution of enzymes may be achieved by injecting a

+ n. A more even distribution of enzymes may be achieved by injecting a tenderizing solution of papain (proteolytic enzymes) , into the bloodstream of animals 10 min before slaughter, these enzymes are not activated until meat from the animal is exposed to heat during preparation. This process not only increases tenderness, but shortens the time of rigor mortis and aging.

+ 2 - Salts: n Tenderness can also be increased by the addition of

+ 2 - Salts: n Tenderness can also be increased by the addition of salts in the form of potassium, calcium or magnesium chlorides. n These salts retain moisture and break down the component that surrounds the muscle fibers, resulting in the release of proteins.

+ 3 - Acids: n Applying of acids (vinegar, lemon, tomato or other fruits

+ 3 - Acids: n Applying of acids (vinegar, lemon, tomato or other fruits juices) tenderize meat by break down the outside surface of the meat. n Also they flavor and contribute to the color. n The maximum benefits can be obtained by increasing the surface area of the meat, this done by cutting the meat into small pieces. n Acids penetrate only the surface of the meat and therefore acids not effective at tenderizing large cuts of meat. n Meat must allowed to soak in the refrigerator, from half an hour to overnight.

+ 4 - Mechanical tenderization: n Including: n These Grinding, cubing, needling and pounding.

+ 4 - Mechanical tenderization: n Including: n These Grinding, cubing, needling and pounding. actions physically break the muscle cells and connective tissue, making the meat more tender and easier to chew.

+ Preparation of meats n Whether meat is prepared by dry-heat methods or by

+ Preparation of meats n Whether meat is prepared by dry-heat methods or by any of the various moist-heat methods, it should be wiped with a paper towel to remove any surface moisture. n Leaving water on the meat or washing it will result in a faded color and the loss of some water-soluble nutrients and flavor compounds. n After it is wiped the meat can be trimmed of any visible fat or connective tissue to reduce calories, and increase tenderness.

+Changes during heating 1 -Tenderness and juiciness: n Cooking meats at the correct temperature

+Changes during heating 1 -Tenderness and juiciness: n Cooking meats at the correct temperature for the right amount of time will maximize their tenderness, juiciness and flavor. n During heating, the collagen molecule begins to denature at (39°C) and collapses at (65°C) , resulting in a considerable loss of volume and length in the meat. n Exposing meat to high temperatures for too long time will toughen, shrink and harden meat because it shortens muscle fibers, denatures proteins and cause it to dehydrate.

+ Changes during heating n Also, the freeing of some water as the meat's

+ Changes during heating n Also, the freeing of some water as the meat's other protein denature and lose their water-binding capacity. n Longer cooking at lower temperatures makes meat, especially the tougher cuts, more tender, because it breaks down the collagen to gelatin. n Any fat in the meat melts as it is cooked, which increases tenderness, juiciness and flavor.

+ 2 -Flavor changes: n Natural compounds in meat yield that characteristic flavor. Other

+ 2 -Flavor changes: n Natural compounds in meat yield that characteristic flavor. Other factors contribute to flavor as well including: Protein coagulation, melting and breakdown of fats, organic acids and nitrogen containing compounds. n The trace amount of carbohydrates in meat contributes to the special flavor of browned meat surface as these sugars react with proteins in the Maillard reaction, producing the desirable brown color. n Storing meat for over two days in refrigerator or heating leftover meat can result in an unfavorable warmed-over flavor. n The flavor of baked or broiled meat can be enhanced by seasoning.

+ 3 -Determining doneness: Various methods are used to determine doneness and sometimes more

+ 3 -Determining doneness: Various methods are used to determine doneness and sometimes more than one method is used: n Color change: Meat pigments change color as the meat is cooked. Cooking meat initially converts the color of raw meat to bright red. Denaturing of the pigment-containing proteins by heat yields the classic color of well done meat. n Storing cooked meat too long causes the denatured protein to further break down, causing the meat to turn yellow, green or faded.

+ Doneness can be determined by observing the following colors in red meats: q.

+ Doneness can be determined by observing the following colors in red meats: q. Rare: Strong red interior. q. Medium: Rosy pink interior and not quite as juicy as a rare piece of meat. q Well done: Brown interior. No traces of red or pink left. Moist but no longer juicy.

+ n Tough: Doneness can be determined by the firmness of the meat. Pressing

+ n Tough: Doneness can be determined by the firmness of the meat. Pressing lightly on the center of the lean tissue can help to determine whether the meat is rare, medium or well done.

+ Preparation of Meats n Tender cuts are usually prepared by one of the

+ Preparation of Meats n Tender cuts are usually prepared by one of the dry-heating methods: n Roasting (baking). n Broiling and Grilling. n Panbroiling. n Frying.

+ Preparation of Meats n. Less tender cuts of meat are usually prepared by

+ Preparation of Meats n. Less tender cuts of meat are usually prepared by moist-heat methods such as: n. Braising. n. Simmering/stewing. n. Steaming.

+ Storage of Meats n. Meat contains high percentages of water and protein, both

+ Storage of Meats n. Meat contains high percentages of water and protein, both ideal for the growth of microorganisms. n. Consequently, meat should be stored in the refrigerator or freezer. n. Meats are best refrigerated at just above freezing (32°F/0°C), between 32°F and 36°F (0° to 2°C).

+ Storage of Meats Wrapping Meat: n Most retail meats are packaged with plastic

+ Storage of Meats Wrapping Meat: n Most retail meats are packaged with plastic wrap and can be refrigerated in their original wrap for up to two days. Frozen: n Meats to be frozen should be wrapped tightly in aluminum foil, heavy plastic bags, or freezer paper and stored at or below 0°F (- 18°C).