Muscle fiber characteristics, myofibrillar protein isoforms, and meat quality

The objectives of this review were to examine the present knowledge on: (1) the muscle fiber characteristics of skeletal muscle, (2) the diversity of the myofibrillar protein isoforms and their relationship to muscle fiber characteristics, and (3) the understanding of how the effects of the fiber characteristics and protein isoforms influence postmortem metabolism and meat quality, including the technological aspects and sensory characteristics of meat. The histochemical characteristics of skeletal muscle are primarily the result of genetic and environmental factors, including gender, muscle type, breed, age, hormones, exercise, etc. The morphological and biochemical characteristics of muscle fiber are factors that influence energy metabolism in living muscle, but they influence postmortem muscle as well. Muscle fibers are divided into various types, depending on the myosin heavy chain (MHC) isoforms they express. Moreover, not only the MHC, but also the myosin light chain, troponin, and tropomyosin isoforms can influence muscle fiber characteristics. On this basis, the isoform composition of myofibrillar protein can influence postmortem rigor development, and consequently, meat quality. Hence, muscle fiber characteristics and myofibrillar protein isoforms are very useful indicators for examining variations in muscle metabolism at the postmortem period as well as ultimate meat quality. Moreover, such characteristics from live animals can be used to predict meat quality and can be applied in selection programs to improve and control meat quality. Still, however, the effects of the protein isoforms on ultimate meat quality are not yet fully understood. Therefore, to practically apply this knowledge for the improvement and control of meat quality, more information must be gathered on how histochemical and biochemical characteristics influence meat quality in livestock.