Mild Protein Oxidation Enhanced Hydration and Myofibril Swelling Capacity of Fresh Ground Pork Muscle Packaged in High Oxygen Atmosphere

This study investigated the influence of an oxygen-enriched modified atmosphere packaging (HiOx: 80% O(2)/20% CO(2)) in comparison with air-permeable polyvinylchloride (PVC) wrapping and partial vacuum (VP: 60%) packaging on the ability of myofibrils to imbibe water during retail display of fresh ground pork at 2 to 4 degrees C. Both HiOx and PVC muscles after 4 d showed maximum myofibril swelling and A-band dissolution when isolated myofibrils were subjected to a graded series of salt solutions (0.2 -> 0.4 M NaCl with 10-mM sodium pyrophosphate, pH 6.2), while VP samples exhibited no remarkable change. Protein carbonyl content increased substantially from day 0 to 4 in all muscle samples. For HiOx, muscle hydration capacity increased linearly (P < 0.05) during storage up to 14 d, corresponding to protein carbonyl production. No significant changes in hydration properties were noted in VP muscle samples, which also maintained lower levels of protein oxidation, during storage up to 21 d. These results indicated that packaging in modified atmosphere with high levels of oxygen could result in increased protein oxidation but enhanced hydration capacity of fresh meat. Practical Application Packaging of fresh meat, including ground pork, under an oxygen-enriched atmosphere condition is widely used in the industry to preserve red color of meat. Results from the present study indicate that high oxygen packaging has a discordant effect on fresh ground pork: it enhances hydration but decreases water-binding, and this seems to be caused by increased swelling of muscle fibers due to mild protein oxidation. Hence, it is advisable to employ a water-binding agent in this type of packaging system so as to retain the moisture in stored fresh pork products while maintaining the color stability.