Meat composition and nutrition

Meat has exerted a crucial role in human evolution and is an important component of a healthy and well balanced diet due to its nutritional richness. From the nutritional point of view, meat's importance is derived from its high quality protein, containing all essential amino acids and it's highly bio available minerals and vitamins.

1. Meat Composition And Nutrition Ashir Azeem

2. Introduction Nutrients in meat vary with animal breed, feed, season and position of meat cut. Meat contains approximately 75 % water , 19 % protein, 5 % fat with small portion of carbohydrates, free amino acids, dipeptides, nucleotides and minerals. Generally, low fat contents in lean red meat, have less cholesterol level and essential vitamins and minerals.

3. Meat is an excellent source of protein as well as water soluble vitamins and minerals which provide 25 % recommended dietary intake (RDI). Almost 10 % RDI is achieved from riboflavin, pantothenic acid and selenium. The mixture of muscles (84 %), gelatin (16 %) and nitrogen has biological value of 99 whereas biological value of beef is 92 in comparison to biological value (100) of egg protein.

4. Water Water is the most variable component in meat. Its contents are inversely related to the fat but in lesser extent with ash and carbohydrates value. Water contents declines when the animal reaches to the chemical maturity without considering the species of animal. As animal matures, fat content increases while a significant decrease in water content occurs

5. This inverse relationship does not affect the bone content occurs. This inverse relationship does not affect the bone content. Its percentage varies from low (4.5 %) to high (64.5 %). From the kidney knob low water containing meat is obtained whereas over the rib high fat containing meat is obtained.

6. Protein and amino acids Protein are made up of almost 20 amino acids that may be essential and non-essential. Amino acids have a general structural formula:

7. Meat contains essential health promoting constituents like protein, fats, micronutrients, and omega-3 fatty acids. Proteins play a wide range of functions that may be structural, contractile, or enzymes which catalyze the chemical reactions. Proteins contain carbon nitrogen, oxygen, hydrogen and sulphur compounds.

8. Meat and meat proteins are further divided into different fractions: Sarcoplasmic Proteins Sarcoplasmic proteins are also referred to as soluble proteins because they are extracted through water or low ionic salt concentrations. Sarcoplasmic plasmic proteins contain mitochondrial oxidative enzymes, flavin compounds and heme pigments. These posses lyzozymes or nucleoproteins which play a vital role in degrading the waste material and are also helpful in synthesis and deposition of proteins.

9. Mayofibrillar Proteins The major component of meat muscle is myofibril that covers meat about 70 % by volume. Three dimensional structures of filament of the myofibrils provide an open space for water to be immobilized. These proteins are also known as contractile proteins because they play role in muscle contraction.

10. c) Connective Tissue proteins Connective tissue proteins considered as a supporting framework thus plays numerous functions in living body. This fraction of proteins includes collagen, elastin and reticulin , which is less well-defined than the former two.

11. i ) Collagen Collagen is the important fraction of connective tissues which comprises of 20 to 25 % of the total protein content. It is widely present in the body. Collagen is the triple helix of peptide chains coiled with one another to form a single fiber. Collagen is the important protein present in bones, skin and tendons.

12. ii) Elastin Elastin belongs to an unreactive and unique class of proteins. It is a minor component of most tissues, but found in appreciable amounts in the ligaments of the vertebrae and in the walls of large arteries.

13. iii) Reticulin It is chemically similar to collagen and many researchers believe it to be merely another form of collagen. Reticulin fibers are fine, wavy and show some branching.

14. Carbohydrates Immediately after postmortem, muscle containing small amount (about 1 % of glycogen usually disappears before completion of rigor. Both the rate and amount of glycogen breakdown control the physical properties of meat, such as water-holding capacity, color, and tenderness. Rapid glycosis , while the muscle temperature is still high, has been shown to be a causative factor in development of Pale, Soft and Exudative (PSE) muscle in the pig.

15. Similarly , freezing before completion of glycosis has been found to cause excessive muscle shortening, thus contributing to toughness in meat. And if the glycogen and creatine phosphate are all used up before the pH reaches the normal of 5.3 to 5.6, the final pH of meat remains on higher side. The resulting high pH meat is called commonly called “dark cutting” because of its dark appearance and low oxygen uptake.

16. Fat tissue is made up of fat cells embedded in a matrix of connective tissue. Animal fat is composed of neutral fat and phospholipids. The neutral fats are glycerol esters of straight chain carboxylic acids and triglycerides. Triglycerides are present as single or mixed depending on the three fatty acids esterified to the glycerol are same or different. The structural formula represents that all three R- group containing three different or same groups.

17. Phospholipids are present in animals in form of phosphoglycerides . These are found in very minute range from 0.5 % to 1.0 % of lean muscle. Triglycerides are more stable than phospholipids, they are readily oxidized and give off flavor to the meat and meat products. Major contribution of energy comes from fat that is about 2.25 times more than protein and carbohydrates.

18. Fatty acids play an important role in maintaining health. Linoleic acid plays a key role in controlling and showing positive anti-carcinogenic, anti- atherogenic , anti-obesity and anti-diabetic effects. Different sources of fat are helpful in controlling diseases and stimulating interest or arising awareness in people. 40 % of total fatty acids in the lean meat and 48 % with fat meat from a saturated fatty acid portion. Meat is a frequent source of long chain ω -3 PUFAS. The unsaturated fatty acids, linoleic (C 18:2), linolenic (C 18:3) and arachidonic (C 20:4) appear to be essential. They are necessary constituents of cell walls, mitochondria and other intensely active metabolic sites.

19. Vitamins Meat can be regarded as an important dietary source of vitamins, including B1 and B2 as compared to vitamin D. Factors like nature of organ, species and age of animal affect the vitamin content. Organ meat possesses markedly higher concentration of vitamin (A and B12) than muscular tissue. Vitamin level in lean meat tissue is low but is excellent source of folate and vitamin A. Bioavailable vitamins in rich amount can be obtained from meat. e.g. Vitamin B12 2/3 as part and 25 % RDI of riboflavin, niacin, vitamin B6 and panthothenic acid, fulfilling daily requirements in a 100 g serving of meat.

20. Minerals Mineral components vary in several meats. Potassium is quantitatively the most important mineral, followed by phosphorus, except in cured meat where sodium from the added salt predominates. In respect of species differences, the high content of iron in beef no doubt reflects the greater concentration of myoglobin in this species than in mutton. Iron, copper and zinc contents of kidney and liver are much higher than those in muscular tissue.

21. Bioactive Compounds Along with the essential nutrients that have defined requirements, the beneficial effects of a lot of meat based bioactive substances. a) Taurine Taurine is an amino acid in meat which is of high importance. Meat is a high source of taurine at the rate of 110 mg per 100 g in lamb meat and 77 mg per 100 gram in beef. b) Carnitine Long chain fatty acids are transported across the inner membranes of mitochondria, by L- cartinine beta-hydroxyl-gamma- trimethyle amino butyric acid), to produce energy while exercising .

22. c) Conjugated linoleic acid (CLA) CLA can play an important role in control of obesity by the antioxidants and immunoregulatory properties that it possesses. It is abundant in the fat component of the red meat that is 1g/100g. d) Creatine There is an important role played by creatine and its phosphorylated derivatives, in muscle energy metabolism and in some conditions its supplements can increase muscle performance. Red meat has about 350 mg per 100 gram.