Some factors causing variation in the texture of similar muscles from comparable animals

This paper reviews recent studies on pre- and postmortem changes in muscle tissue that cause variation in quality of similar muscles from animals of equal age, similar breeding and rearing, and processed under identical conditions. These studies indicate that the nervous state of the animal and struggling at death cause an undesirably high rate of glycolysis and breakdown of high-energy phosphates immediately before or after death in some animals. This results in a low pH at death or shortly after death and a rapid onset of rigor when the temperature of the carcass is still high. These conditions cause denaturation of sarcoplasmic and myofibrillar proteins and excessive shortening-and consequently toughness and loss of water-holding capacity. The extent of these changes varies widely between similar muscles from comparable animals which leads to concomitant variations in tenderness and juiciness of the meat. Another causal factor in this variation is the lack of activation of an intrinsic enzyme system which dissociates the Z-lines and improves tenderness.