Effect of feed on cholesterol concentration and oxidation products development of longissimus dorsi muscle from Iberian pigs

The effect of dietary free-range feeding or supplementation with copper and/or vitamin E in confinement on total cholesterol, neutral and polar lipids and cholesterol oxidation of the longissimus dorsi muscle from Iberian pigs was studied. Free-range fed pigs had higher (P=0.001) contents of gamma-tocopherol and lower concentrations of alpha-tocopherol in the muscle than pigs fed diets supplemented with 100 mg/kg vitamin E. The total cholesterol content of the muscle was not significantly affected by the diets. However, the cholesterol:phospholipid ratio was higher (P<0.05), and consequently the membrane fluidity was lower, in the free-range fed pigs than in the pigs fed in confinement with either copper-supplemented (P<0.05) or vitamin E-supplemented (P<0.01) diets. The proportion of saturated fatty acids in phospholipids was greater (P<0.05) in the free-range fed group, which suggests metabolic regulation to maintain membrane structure. Free-range feeding produced higher levels of free fatty acids (P<0.01), lysophosphatidylcholine (P<0.05) and phosphatidylserine (P<0.01) and lower cholesterol esters (P<0.01) and sphingomyelin (P<0.05) in the muscle than the other groups. The ratios of phosphatidylethanolamine:phosphatidylcholine and sphingomyelin:phosphatidylcholine, which are indicators of membrane fluidity, were not significantly affected in any group. Dietary alpha-tocopheryl acetate supplementation produced lower beta-epoxide (P<0.01), 7beta-OH (P<0.05), and total cholesterol oxides (P<0.01) in cooked muscle after refrigerated display than in the other groups. These results indicate that supplementation with dietary alpha-tocopheryl acetate is more effective in reducing cholesterol oxidation than free-range feeding in cooked muscle from Iberian pigs. In evaluating oxidation, the composition of the muscle and meat treatment have to be considered as well as membrane fluidity.