Effects of light, oxygen diffusion, and 4-hydroxy-2-nonenal on redox stability of beef and porcine myoglobin

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) is an ɑ-, β-unsaturated aldehyde derived from the oxidation of n–6 polyunsaturated fatty acids. HNE-induced bovine and porcine 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 open/closed systems. Therefore, the objective was to examine the effects of light and dark storage conditions (experiment 1) as well as to compare open and closed systems (experiment 2) on HNE-induced bovine and porcine OxyMb oxidation at 4°C. Bovine and porcine OxyMb (0.650 mM; pH 5.6) was mixed with HNE (4.5 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 (1,510 lux) or dark conditions (experiment 1). Metmyoglobin (MetMb) formation was measured spectrophotometrically on days 0, 2, 4, 6, and 8 of incubation (experiment 1). In experiment 2, FireflySci Type 46 semi-micro spectrophotometer cuvette cells with SEPTA closed screw caps were used for open (allowing exposure to atmospheric oxygen) and closed (no diffusion of oxygen from outside) systems. MetMb formation was calculated spectrometrically on days 0, 1, 2, 3, and 4 of incubation. The experiments were replicated three times. The presence of light and HNE increased (P < 0.05) bovine and porcine MetMb formation (bovine > porcine). HNE-induced beef OxyMb oxidation was greater (P < 0.05) in an open system than in a closed system. Bovine myoglobin samples with and without HNE had greater metmyoglobin than porcine myoglobin samples with and without HNE when kept in an open system. These findings indicated the potential impact of retail display conditions on species-specific lipid oxidation-induced meat discoloration.