Composition of Meat - Water, Carbohydrates, Minerals and Vitamins

Jun 08, 2017

The most abundant chemical in meat is water followed by protein then fat. Carbohydrates, minerals and vitamins occur on much smaller amounts but nevertheless are very important metabolically and nutritionally.

Water

Adipose tissue contains little moisture; therefore, the fatter the animal, the lower the total water content of its carcass or cuts. Beef muscle from mature and relatively fat animals may contain as little as 45 percent moisture, while veal muscle from very youthful and relatively lean animals may contain as much as 72 percent moisture. Texture, color and flavor of muscle are affected by the amount of water in muscle tissue. 

A large percentage of the water in muscle tissue exists as free molecules within the muscle fibers; a smaller percentage is located in the connective tissue. it is  possible for some of the water to remain  (during storage, curing and heat treatment) within muscle fibers because of  the three-dimensional structure of the  fibers; water retained under forces of  pressure and temperature increase is  termed “bound water;" that which is  lost is called “free water’ The water-  holding capacity of the muscle can be  decreased by disruptions of muscle  structure. Grinding, chopping, freezing, thawing, salting, degradation of connective tissue by enzymatic or chemical means, application of other chemicals or organic additives that change acidity (pH), and heating are treatments that can affect the final water content of meat products. 

Carbohydrates

 The primary carbohydrate reservoir of the animal body is the liver. That organ contains about one—half of the carbohydrates found in the body. Carbohydrates are stored as glycogen in the liver and in muscles. The remaining SO percent of carbohydrates are distributed throughout the body, largely in the muscles, but with substantial quantities in the blood (usually as glucose) and in other tissues, organs and glands. 

The changes that occur in energy metabolism, e.g., the conversions of glycogen to glucose and glucose to lactic acid, are complex; all such changes are controlled and mediated by enzymes and hormones. The lactic acid content of the muscles in a carcass increases during initial stages of aging or ripening, lowering the pH (muscle acidity). The pH of muscle considered “normal” is 5.6 (pH is the negative log of the hydrogen ion concentration; the higher the pH, the less acidic is the muscle). Muscle color, texture, water-holding capacity and tenderness are influenced by pH.  If an animal experiences vigorous stress  or exercise of the muscles immediately  prior to slaughter and has no opportunity to restore its normal glycogen  levels, the glycogen content within the  muscles at slaughter will be reduced  substantially. Because so little glycogen  is available to be converted (after death)  to lactic acid, a higher ultimate pH  (e.g., a final pH of 6.2) will occur in this  animal's muscles after slaughter, and the  muscles will be dark, firm and dry  (DFD). This is a reasonably rare occurrence in beef (perhaps 2 percent of carcasses are affected) and those carcasses are termed “dark cutters’ The DFD condition also occurs in pork and lamb carcasses. It is thought that the dark color of muscles with a high pH is due to its higher water-holding capacity, which causes muscle fibers to be swollen. The swollen state of the fibers causes more incidents light to be absorbed, rather than reflected, by the meat surface, and thus the color appears to be darker.  “Dark cutters" are severely discounted in price by packers and retailers, due to poor consumer appeal of this meat; therefore, stress and rough handling of animals is minimized prior to slaughter.

 A too—rapid postmortem (after death) drop in muscle pH (to a final pH of 5.1, for example) is associated with the pale, soft, and exudative (PSE) conditions that are somewhat common in pork muscle.  PSE muscle is characterized by soft and mushy texture, low water-holding capacity and pale muscle color. The looser muscle structure of PSE muscle associated with its lower water-holding capacity is responsible for a greater reflectance of incident light and hence it has a pale color.

Minerals and Vitamins 

 In addition to protein and fat, meat (beef, veal, pork and lamb) is a significant source of several other nutrients in the U.S. diet. These include the minerals iron and zinc, and most of the B—vitamin complex (B1, B2, niacin, B6 and B12).

 

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