Effect of dietary supplementation on cholesterol photoxidation of beef meat, during storage under commercial retail conditions

The effects of feeding composition on the photoxidative stability of lipids from beef meat, were evaluated during storage under commercial retail conditions. Feeding was enriched with various ingredients (linseed oil, vitamin E and conjugated linoleic acid (CLA)) at various doses, leading to 7 independent diet groups: control (A), linseed oil/vitamin E for 180 days (B), linseed oil/vitamin E for 90 days (C), CLA /vitamin E for 180 days (D), CLA/vitamin E for 90 days (E), linseed oil/CLA/vitamin E for 180 days (F) and linseed oil/CLA for 180 days (G). Meat slices were packed in vessels with transparent shrink film (half of them were covered with aluminum foil -T8D-) and subjected to photo-oxidation with a white fluorescent light for 8 h at 8°C (T8L). Cholesterol oxidation products (COPs) and sterol content were determined before and after photo-oxidation. Total sterol content ranged from 399 to 1343 mg/100 g lipids, which corresponded to 283 and 514 ppm of meat. Total cholesterol was about 98% of total sterols, whereas phytosterols were 2%. The main phytosterol was campesterol (38% of phytosterols), followed by sitosterol (27%), stigmasterol (19%) and 5-avenasterol (16%). In general, vitamin E increased the oxidative stability of beef meat subjected to photo-oxidation under commercial retail conditions. The highest amount of COPs (11.7-39.1 ppm of lipids and 0.5-2.1 ppm of meat) were found in the group B, whereas the lowest amount was observed in group E. Cholesterol oxidation rate varied between 0.1 and 0.6% of total cholesterol. After light exposure, 7-ketocholesterol, 7α-hydroxycholesterol and 7β-hydroxycholesterol increased, whereas 5,6α-epoxycholesterol and 5,6β-epoxycholesterol decreased.