Protein oxidation in living tissues is known to play an essential role in the pathogenesis of relevant degenerative diseases, whereas the occurrence and impact of protein oxidation (Pox) in food systems have been ignored for decades. Currently, the increasing interest among food scientists in this topic has led to highlight the influence that Pox may have on meat quality and human nutrition. Recent studies have contributed to solid scientific knowledge regarding basic oxidation mechanisms, and in advanced methodologies to accurately assess Pox in food systems. Some of these studies have provided insight into the reactions involved in the oxidative modifications undergone by muscle proteins. Moreover, a variety of products derived from oxidized muscle proteins, including cross-links and carbonyls, have been identified. The impact of oxidation on protein functionality and on specific meat quality traits has also been addressed. Some other recent studies have shed light on the complex interaction mechanisms between myofibrillar proteins and certain redox-active compounds such as tocopherols and phenolic compounds. This paper is devoted to review the most relevant findings on the occurrence and consequences of Pox in muscle foods. The efficiency of different anti-oxidant strategies against the oxidation of muscle proteins is also reported.

An overview of myoglobin-initiated lipid oxidation in simple model systems, muscle, and muscle-based foods is presented. The potential role of myoglobin spin and redox states in initiating lipid oxidation is reviewed. Proposed mechanisms for myoglobin-initiated lipid oxidation in muscle tissue (pH 7.4) and meat (pH 5.5) are evaluated with the purpose of putting forward general mechanisms explaining present observations regarding the catalytic events.

Poly(N-isopropylacrylamides) grafted with varying amounts of poly(ethylene oxide) (PNIPAg-PEO) were synthesized and studied with differential refractometry, differential scanning calorimetry, and dynamic light scattering. By free radical reaction between N-isopropylacrylamide (NIPA) and either N-acryloylsuccinimide (NASI) or glycidyl methacrylate (GMA), two functional copolymers, PNIPA-co-NASI (M w ) 1.9 × 10 5 ) and PNIPA-co-GMA (Mw ) 1.8 × 10 5 ), were synthesized. Various amounts of PEO (Mw ) 6000) were attached to the functionalized backbones either in dioxane or in water. Thermal behavior of PNIPA-g-PEO copolymers in aqueous solutions both below and above LCST depends on the amount of PEO grafts and on the polymer concentration. Above the LCST, the size of the aggregates of the graft copolymers sterically stabilized by a low number of PEO grafts is dependent on these two factors. Factors determining the shrinking and collapse of PNIPA-g-PEO include hydrophobic interactions, intraand interchain interactions, and the solubilizing effect of PEO on the shrinking backbone.

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