Determining the Effects of Light, Oxygen Diffusion, and 4-Hydroxy-2-Nonenal on Redox Stability of Beef and Pork Oxymyoglobins

Retail light conditions influence consumers’ perception of meat color. Previous studies have shown that lipid and myoglobin oxidation are interrelated. 4-Hydroxy-2-nonenal (HNE)-induced beef and pork oxymyoglobin (OxyMb) oxidation is influenced by pH, temperature, and atmospheric oxygen partial pressure. However, limited knowledge is available on the effects of HNE on myoglobin redox stability under light/dark and aerobic/anaerobic (either allow or not allow atmospheric oxygen in contact with myoglobin solution) systems. Therefore, the objective was to examine the effects of light and dark storage conditions (experiment 1) as well as to compare aerobic and anaerobic systems (experiment 2) on HNE-induced beef and pork OxyMb oxidation at 4°C. Beef and pork OxyMbs (0.085 mM; pH 5.6 and pH 7.4) were mixed with HNE (0.6 mM), whereas controls received an equal volume of ethanol equivalent to delivering HNE. Following mixing, the samples were incubated at 4°C under a continuous fluorescent light source (1,583 lux) or dark conditions (experiment 1). Metmyoglobin (MetMb) formation was measured spectrophotometrically for 6 (for pH 5.6) or 8 d (for pH 7.4) of storage (experiment 1). In experiment 2, closed screw caps were used for aerobic (allowing exposure to atmospheric oxygen) and anaerobic (no diffusion of oxygen from outside) systems. MetMb formation at pH 5.6 was calculated spectrometrically on days 0, 2, 4, and 6 of storage. The experiments were replicated 3 times. The presence of light and HNE increased (P < 0.05) beef and pork MetMb formation (beef > pork; P < 0.05). HNE-induced beef OxyMb oxidation was greater (P < 0.05) in an aerobic system than in an anaerobic system. Beef myoglobin samples with and without HNE had greater MetMb than pork myoglobin samples (P < 0.05) with and without HNE when kept in an aerobic system. These findings indicated the potential impact of retail display conditions, such as light or aerobic conditions, on species-specific lipid oxidation–induced meat discoloration.