Physiology and Biochemistry of Collagen

Variations in the amounts and composition of intramuscular connective tissue (IMCT) have long been a strong element in studies on meat texture (Marsh 1977; Bailey and Light, 1989). Although focus in the last twenty years has firmly switched to postmortem proteolysis of myofibrillar and cytoskeletal components (Koohmaraie et al., 1991; Taylor et al, 1995; Sentandreu et al, 2002), the link between IMCT content of a muscle and cooked meat texture is inextricably bound up in retail pricing of various cuts of meat; variations in price between shin beef and fillet steak principally reflect expectations of tenderness, based largely on variations of IMCT content. Likewise, the increase in toughness of meat from older animals in all species used for meat results from increased thermal and mechanical stability of IMCT with age, and is reflected in a preference for meat from less mature animals. Modern production practices clearly aim to minimise variations in texture due to IMCT maturity, and within young animals of a narrow age range and of the same breed, variations in texture of a given muscle after aging (post mortem conditioning) are only minimally related to collagen content and solubility (e.g. Renand et al., 2001). This has led to a view that IMCT provides a “background toughness” (Ouali et al., 1992), which is somewhat fixed. In addition to reviewing major elements of the role of IMCT in cooked meat toughness, my aim is also to point out sources of variation in expression of IMCT within muscle and its turnover, as potential targets for manipulation so as to improve meat texture.