Effects of oxygen concentrations in modified atmosphere packaging on pork quality and protein oxidation

This study aimed to investigate the effects of oxygen concentrations in modified atmosphere packaging (MAP) on pork color and protein oxidation under refrigerated storage. Pork steaks were vacuum packaged or MAP packed with different levels of oxygen (40%, 60% and 80%), and stored for 14 days at 4 °C. After storage, the instrumental color, purge loss, cooking loss and shear fore were measured, and levels of protein oxidation in both the sarcoplasmic and myofibrillar proteins were quantified separately by the determination of carbonyl contents, thiol contents, loss of specific amino acid residues, and formation of α-aminoadipic semialdehyde. Results suggested that 40% of oxygen in MAP was sufficient to obtain highest redness, and higher oxygen levels showed little improvement but led to further protein carbonylation and meat toughening. Meanwhile, the sarcoplasmic proteins seemed to be more vulnerable to protein oxidation than the myofibrillar proteins. In particular, the formation of α-aminoadipic semialdehyde might contribute little to the carbonylation of both protein fractions, and possible reasons were discussed.