Update on Muscle-Fiber Type and Meat-Sensory Quality

Meat sensory quality exhibits high variability that is not fully captured by current grading systems. It depends on the biological characteristics of muscles in relation to species, breed, production system, sex, and age of animals, as well as on the biological changes occurring during postmortem ageing. Among biological traits, the role of muscle-fiber type remains less clearly defined than that of intramuscular fat or connective tissue. This review synthesizes knowledge on muscle-fiber types and meat-sensory quality and discusses their potential implications for prediction of meat quality. Muscle fibers are generally classified into slow oxidative, fast glycolytic, intermediate and hybrid fibers according to their contractile and metabolic properties (myosin heavy chain [MyHC] isoforms, metabolic pathways, and other physiologic characteristics). Multiple techniques are available for muscle-fiber typing, ranging from histochemical staining to immu- nohistochemistry and high-throughput omics-based approaches, which facilitate the identification of new molecular biomarkers. Muscles rich in oxidative fibers have typically a red color, more intramuscular fat, and enhanced flavor and juiciness. In contrast, glycolytic muscles are pale, lean and have faster postmortem glycolysis. However, the influence of fiber type on meat quality depends on multiple interacting factors, including the methodologies used for both fiber typing and meat-quality assessment, as well as ageing and cooking conditions. Thanks to genomics and metabolomics, new biomarkers related to fiber type have been identified, though the links between fiber characteristics and meat quality remain complex. Future integration of muscle-fiber biomarkers into predictive models of eating quality will require rapid and cost-effective analytical methods and stronger evidence linking fiber traits to sensory traits. The most advanced grading systems at the cut level are flexible enough to incorporate this type of marker. However, when up to date, they integrate factors that regu- late muscle biomarkers, including animal and carcass characteristics, slaughter conditions, ageing, and cooking methods.