In order to explore the effects of light and oxygen on the storage quality of beef and the physicochemical properties of myofibrillar protein, the pH, color, total volatile basic nitrogen (TVB-N) content, malondialdehyde (MDA) content, microstructure, peptide composition, carbonyl, sulfhydryl and dimeric tyrosine contents of protein in fresh beef were determined during 0–5 days of storage at 4 ℃. The results showed that under natural storage conditions (aerobic, natural light and 4 ℃), the TVB-N and MDA contents increased with storage time, exceeding the standard limit on day 5; the microstructure of beef changed with the occurrence of crosslinking and degradation fragments, and its quality deteriorated and was no longer fit for consumption. Anaerobic and dark conditions could delay beef quality deterioration. As storage time increased, the carbonyl content of myofibrillar protein gradually increased, and the sulfhydryl content gradually decreased. Oxygen could more accelerate the increase of carbonyl groups than light, while light was more effective in reducing sulfhydryl groups. In summary, fresh beef should not be stored for four days under light and aerobic conditions. Light and oxygen can promote protein oxidation and cross-linking aggregation.

Protein oxidation occurs during the manufacture of meat products, which can result in nutrient loss, reduced edibility, and even the formation of some dangerous chemicals that are detrimental to human health. Oxidative modifications of proteins can change their physicochemical properties (conformation, structure, composition, solubility, rheology and reactivity). However, moderate protein modification can also play a role in regulating the quality of meat products. The most important and effective reactive oxygen species (ROS) involved in meat protein oxidation is hydroxyl radicals (·OH), and the Fenton reaction is one of the main pathways for the production of highly reactive hydroxyl radicals. Therefore, this paper reviews the basic principles and products of protein oxidation in the Fenton system and the effect of protein oxidation during meat processing on the color, tenderness and water-holding capacity (WHC) of meat products in order to provide theoretical support for the quality control of meat products.

The catfish fillets were soaked in sterile water (CK), 3.0 mg/mL chlorogenic acid (CGA) solution, 1.0 mg/mL chitosan (CTS) solution, or a mixed solution of 3.0 mg/mL CGA and 1.0 mg/mL CTS (C +) and stored at low temperature. The effects of the CTS-CGA preservative mixture on the eating quality of catfish fillets were analyzed by comparing the changes in cooking loss rate and the changes in shear force, microstructure, water distribution and volatile components of cooked fish fillets as a function of storage time. The results showed that with increasing storage time, the cooking loss rate of catfish fillets increased; for cooked fillets, the shear force decreased, the arrangement of muscle fibers changed from ordered to disordered, and the mobility and relative content of water decreased gradually. After 6 days of storage, the relative content of off-flavor substances was markedly higher in the CK group than in the C + group. The relative contents of hexanal and trimethylamine in the CK group were 40.11% and 8.87%, respectively. The relative content of hexanal in the C + group was only 5.33%, and no trimethylamine was detected, indicating that the CTS-CGA preservative mixture could effectively inhibit the production of undesirable flavor. In conclusion, the CTS-CGA preservative mixture can effectively delay the texture deterioration and maintain the eating quality of catfish fillets.