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 0.52mg/100g meat (average value of 0.27mg COPs/100g meat), which was twice as much as the average COPs content (0.14mg/100g) of meat packed under air (0.04-0.27mg COPs/100g meat). The main cholesterol oxide was 7k, which represented about one third of the total cholesterol oxides, followed by 7β-OH (20-25% of total COPs), 7α-OH (about 20%) and β-epoxy (12-18%). In normal atmosphere, photoxidation was a superficial process, since an inverse correlation between meat slice weight and COPs content on a lipid basis was observed, unlike in a high oxygen (32%) atmosphere.