Muscle Protein Oxidation and Functionality: A Global View of a Once-Neglected Phenomenon

Muscle is a highly organized apparatus with a hierarchic microstructure that offers the protection of cellular components against reactive oxygen species (ROS). However, fresh meat immediately postmortem and meat undergoing processing become susceptible to oxidation due to physical disruption and the influx of molecular oxygen. Upon the activation by endogenous prooxidants, oxygen species are rapidly produced, and both myofibrillar and sarcoplasmic proteins become their primary targets. Direct ROS attack of amino acid sidechains and peptide backbone leads to protein conformational changes, conversion to carbonyl and thiol derivatives, and subsequent aggregation and polymerization. Interestingly, mild radical and nonradical oxidation enables orderly protein physicochemical changes, which explains why gels formed by ROS-modified myofibrillar protein have improved rheological properties and binding potential in comminuted meat and meat emulsions. The incorporation of phenolic and other multifunctional compounds promotes gel network formation, fat emulsification, and water immobilization; however, extensive protein modification induced by high levels of ROS impairs protein functionality. Once neglected but now recognized to be a natural occurrence, protein oxidation has drawn much interest and is being intensively studied within the international community of meat science. This review describes the history and evolution of muscle protein oxidation, the mechanism and functionality impact hereof, and innovative oxidant/antioxidant strategies to control and manipulate oxidation in the context of meat processing, storage, and quality. It is hoped that the review will stimulate in-depth discussion of scientific as well as industrial relevance and importance of protein oxidation and inspire robust international collaboration in addressing this underappreciated challenge.