Chemistry and nutrient composition of meat

Regardless of the animal, lean muscle usually consists of approximately 21 percent protein, 73 percent water, 5 percent fat, and 1 percent ash (the mineral component of muscle). These figures vary as an animal is fed and fattened. Generally, as fat increases, the percentages of protein and water decrease.

Protein. Meat is an excellent source of proteins which carry out specific functions in living muscle tissue and in the conversion of muscle to meat. They include actin and myosin (myofibrillar proteins), glycolytic enzymes and myoglobin (sarcoplasmic proteins), and collagen (connective tissue proteins). Because the proteins found in meat provide all nine essential amino acids to the diet, meat is considered to be a complete source of protein.

Fat. Fats, in the form of triglycerides, accumulate in the fat cells found in and around the muscles of the animal In the diet the fats found in meat act as carriers for the fat-soluble vitamins (A, D, E, and K) and supply essential fatty acidsffiatty.

A beneficial characteristic of saturated fatty acids is that they do not undergo oxidation when exposed to air. However, the double bonds found in unsaturated fatty acids are susceptible to oxidation, and this oxidation promotes rancidity in meat. Therefore, products higher in saturated fats can generally be stored for a longer time i without developing unpleasant flavours and odours.

Vitamins and minerals. Meat contains a number of essential vitamins and minerals. It is an excellent source of many of the B vitamins, including thiamine, choline, B 6, niacin, and folic acid. Some types of meat, especially liver, also contain vitamins A, D, E, and K. Meat is an excellent source of the minerals iron, zinc, and phosphorus, a number of essential trace minerals, such as copper, molybdenum, nickel, selenium, chromium, and fluorine having been found in meat as well.

Cholesterol. Cholesterol is a constituent of cell membranes and is present in all animal tissues. Leaner meats typically are lower in cholesterol. Veal, however, is an exception: it is lower in fat than mature beef but has significantly higher cholesterol levels.

Carbohydrates. Meat contains virtually no carbohydrates. This is because the principal carbohydrate to be found in muscle, the complex sugar glycogen, is broken down in the conversion of muscle to meat. Liver is an exception, containing up to 8 percent carbohydrates.

Water. Water is the most abundant component of meat. However, because adipose tissue contains little or no moisture, as the percentage of fat increases in a meat cut, the percentage of water declines. Therefore, lean young veal may be as much as 80 percent water, while fully fattened beef may be as little as 50 percent. Because water is lost when meats are cooked, the percentages of protein and fat in cooked meats are usually higher than in the raw counterparts.

Text 3