Cholesterol photosensitised oxidation of beef meat under standard and modified atmosphere at retail conditions

The effect of the fluorescent light exposure and type of packaging (normal atmosphere and oxygen-rich atmosphere) was evaluated on the oxidation parameters (peroxides and cholesterol oxidation products) of raw beef slices placed in packed vessels and refrigerated. The concentration of COPs in meat treated under modified atmosphere ranged from 0.15 to 0.52 mg/100 g meat (average value of 0.27 mg COPs/100 g meat), which was twice as much the average COPs content (0.14 mg/100 g) of meat packed under air (0.04 to 0.27 mg COPs/100 g meat). The main cholesterol oxide was 7k, which represented about one third of the total cholesterol oxides, followed by 7beta-OH (20-25% of total COPs), 7alfa-OH (about 20%) and beta-epoxy (12-18%). In normal atmosphere, photoxidation was a superficial process, since an inverse correlation between meat slice weight and COPs content on lipid basis was observed, unlike in high-oxygen (32%) atmosphere.