Types of meat
Color of the lean and character and amount of fat are the two beast indices for identification of the animal from which the meat comes. The color of beef when freshly cut is a dark, purplish red. This changes to a bright, cherry red when the meat is exposed to oxygen. The change in color from purplish red to bright red is reversible. With prolonged exposure to oxygen, the pigment is oxidized and loses its bright red color. Veal, too young to have accumulated as much pigment as the older beef animals, is grayish-pink and the bones have a pinkish tinge. The lean of lamb is a darker, deeper red than beef. The paler rose-pink of fresh pork is due at least in part to the high proportion of white, myoglobin-free muscle fibers interspersed among the red, myoglobin-rich ones(15). The species difference in this regard is illustrated by the whale which is so richly endowed with oxygen-storing red muscle fibers that it can stay submerged without breathing for many minutes(1), whereas the rabbit has a high proportion of white glycolytic muscle fiber that provides not only rapid takeoff but also early oxygen depletion, and thus a biochemical basis for the “scared rabbit” reputation.
The fat of pork with its higher unsaturated fatty acid content is much softer than that from either beef or lamb. Lamb fat is the hardest of all, in fact, is quite brittle. It is usually whiter than beef fat, which tends to be more yellow especially if the animal has been fattened for market by grazing.
In addition to the color of the lean and the character of the fat, the size and contour of a cut are also a clue to the source of the meat. The size and shape clearly differentiate a loin chop of lamb, a center cut pork chop, and a T-bone steak from beef.