Post-mortem Muscle Metabolism and Meat Quality

PSE, DCB and DFD meat are stress-related conditions. PSE meat occurs in pigs and turkeys. In pigs it is common in particular breeds which are known as stress-sensitive (SS) or halothane-positive (nn) genotypes. This chapter focuses on some of the key features in post-mortem muscle metabolism which lead to these meat quality problems, and so helps to explain how preslaughter stress influences meat quality. When an animal is slaughtered, its muscle continues to metabolize energy, contract and produce heat. Some of the energy is used to power the convulsions, muscle twitching (fasciculations) and rigor contractions which occur in the carcass, and some is used in non-contractile biochemical changes. During muscle contraction, adenosine triphosphate (ATP) is utilized and it forms adenosine diphosphate (ADP) and free phosphate (Pi). ATP breakdown provides the energy needed for the contractions. ATP is also utilized in pumping mechanisms that regulate the concentration of ions in the cell. ATP is resynthesized in two main ways. The first is from an energy store which is in the form of creatine phosphate (CP). Creatine phosphate passes on a high energy phosphate group to ADP, forming ATP, in a reaction that is catalysed by the enzyme, creatine phosphokinase (CPK): Chapter 6