Lipid peroxidation in swine and warmed-over flavor in pork: Influences of iron, vitamin E, and vitamin C

Peroxidation of unsaturated fatty acids may produce off-flavors in foods and increase risk of cancer and heart disease in humans. Objectives of this research were: (1) to determine whether iron supplementation of swine rations at levels common in the industry promotes lipid peroxidation and warmed-over aroma (WOA) in cooked pork; (2) to determine whether moderate iron loading in swine promotes lipid peroxidation in vivo; and (3) to study the influence of supplemental vitamins E and C on iron-induced lipid peroxidation in vivo and in cooked pork.; Two swine feeding studies were conducted. In the first, fifteen feeder pigs were divided into three groups and fed to market weight on corn-soy rations containing the usual iron supplement (209 mg Fe/kg diet), no iron supplement (131 mg Fe/kg diet), or no supplement and low-iron dicalcium phosphate (62 mg Fe/kg diet). Removal of the iron supplement reduced lipid peroxidation (lower thiobarbituric acid-reactive substances (TBARS)) and nonheme iron (NHI) in cooked pork (p {dollar}<{dollar} 0.05) but did not affect WOA as perceived by a trained sensory panel. TBARS and WOA, TBARS and NHI, and NHI and WOA were positively correlated. In the second study, twenty-four weanling pigs were given 1400 mg iron in a series of iron dextran injections to produce moderate iron loading. They were fed for 8 wk on corn-soy rations supplemented with vitamin E (200 IU/kg diet), vitamin C (2000 mg/kg diet), both, or neither. Six control pigs received 100 mg iron dextran and were fed standard swine rations. Mean TBARS {dollar}pm{dollar} SE in livers removed at slaughter were: 175.10 {dollar}pm{dollar} 26.78 (Fe-only), 138.73 {dollar}pm{dollar} 22.28 (Fe+C); 83.65 {dollar}pm{dollar} 3.58 (Fe+E); 61.41 {dollar}pm{dollar} 5.84 (Fe+E+C); 66.05 {dollar}pm{dollar} 6.20 (Control) nmole malondialdehyde/g wet wt. Supplementation with E+C improved oxidative stability in cooked pork and color stability in raw pork. Supplementation with vitamin E suppressed liver iron stores by 30%.; Summary. Reduction of iron levels in swine rations will not substantially improve oxidative stability of cooked pork. Oxidative stress in pigs is increased by moderate iron loading but the effect can be prevented by supplementation with vitamin E.