Extracellular modifications to muscle collagen: Implications for meat quality

The extracellular matrix (EMC) of muscle is composed mostly of the protein collagen with lesser quantities of other constituents such as proteoglycans also present. The focus of this brief review is the extracellular modifica tion of collagen, critical to forming a stable matrix, called crosslinking. Enzyme-mediated covalent collagen crosslinks are largely lysine-derived. T heir formation is absolutely essential for stabilization of the EMC and a f unctional muscle. In cooked meat, the presence of crosslinks contribute to the shrinkage and tension development of collagen as it denatures with a su bsequent increase in the toughness of meat. Both crosslink and collagen con centrations vary with differing muscle type, producing a wide range of text ural differences among muscles. Furthermore, within a given muscle type, a wide range of conditions, often dependent on management choices, influence crosslinking patterns. Although information regarding the chemical structur e, specific location, and quantity of collagen crosslinks is available, mec hanisms that control and regulate their formation remain elusive. Recent st udies, however, suggest a potential role for the proteoglycan decorin in re gulating collagen fibrillogenesis, ordering the spatial arrangement of coll agen molecules and, thus, influencing crosslinking patterns.