Adipose (Fatty) Tissue

Adipose tissue is, simply, fat, which serves as insulation under the skin (subcutaneous) and as padding in the abdominal cavity for sensitive internal organs. This fat when it appears on the outside of meat is known as cover fat, and is generally trimmed to a minimum before cooking. Fat found within muscles is called intramuscular fat or marbling. When meat is cooked, these fat deposits melt and contribute to perceived flavor and juiciness. For this reason, marbling is a factor in the grading of meats. The cover fat surrounding meats helps retain the moisture of meats, but this separable fat is often trimmed off meats prior to preparation. For content varies widely among meats and is dependent on the source animal’s genetics, age, diet, and exercise, and on the cut of the meat.

Well-marbled beef fetches a higher price so many cattle ranchers, in an attempt to improve marbling, feed cattle richer grain during the last weeks or months before slaughter. Paradoxically, however, with the consumer trend in recent years away from fatty meats, some ranchers are raising lower-fat beef to meet consumer demands. Some livestock are being bred to average 25-30 percent fat. Similarly, a recent technique in swine livestock management is the use of a growth hormone somatotropin, which result in leaner animal.

The animal’s age, diet and species also affect the color and texture of fat. It is white in younger animals, and turns progressively more yellow as the animals age because of the presence of carotenoid pigments in the feed. Feeding-lot practices that provide swine with fats that are primarily saturated will yield pork fat that is more saturated and hard. Conversely, including more polyunsaturated fatty acids in the animal’s diet will make its fat softer. The species and breed of the animal also influence the softness of fat; beef fat, for example, is very different from the hard, more brittle and dense fat observed in lamb.