The Structure of Meat and Its Colour

Physically, skeletal muscle consists of long bundles of very thin fibres, each fibre representing an individual cell. Collectively, these bundles give the ‘grain’ apparent when muscles are cut across. The basic chemistry of meat exploits the properties of two proteins which allow voluntary movement in animals. These are actin and myosin which exist as long molecules lying parallel to each other in muscle fibres. When muscles contract, electrical impulses cause the two proteins to slide past each other and bond, forming a complex molecule known as actomyosin, shortening and holding the position. The fibre bundles are supported by fine sheets of connective tissue and are attached to the bones by tendons; the protein collagen is important in these tissues. Protein accounts for about 18 per cent of the total weight of lean raw muscle, water represents about 75 per cent, and fat 3 per cent. Most of the water is held mechanically within the structure of the muscle, although a small proportion is chemically bound to the protein. Proportions vary according to species, and joints of meat usually include more fat in the form of visible layers.