A. Asghar

Effect of dietary vitamin E on the stability of raw and cooked pork

Experiments were designed to investigate the effects of dietary α-tocopherol supplementation for 2 weeks prior to slaughter on plasma and muscle α-tocopherol levels and on the oxidative stability of raw and cooked pig muscle during refrigerated storage at 4°C. Plasma and muscle α-tocopherol levels of the pigs on the α-tocopherol supplemented diet (200 mg α-tocopherol acetate/kg feed) were ∼2·5-fold higher than those of the pigs on the control diet (30 mg α-tocopherol acetate/kg feed). Dietary supplementation with α-tocopherol significantly (p < 0·01) improved the oxidative stability of both raw and cooked muscle after storage at 4°C for up to 8 days. α-Tocopherol stabilized the membrane-bound lipids against metmyoglobin/H(2)O(2)-initiated oxidation and also significantly (p < 0·05) improved the oxidative stability of rendered fat.

Effects of oxidised dietary oil and antioxidant supplementation on broiler growth and meat stability

1. Broilers were fed on diets containing oxidised sunflower oil, sunflower oil and sunflower oil supplemented with alpha-tocopherol, butylated hydroxyanisole (BHA) or butylated hydroxytoluene (BHT). 2. Oxidised oil caused a significant reduction in broiler body and carcase weights, whereas alpha-tocopherol and BHA/BHT supplementation improved growth. 3. Meat samples from these broilers were stored at 4 degrees C and -20 degrees C and their oxidative stability evaluated. Feeding oxidised oil to broilers resulted in meat that underwent rapid oxidative changes during refrigerated and frozen storage. 4. On the other hand, dietary alpha-tocopherol and BHA/BHT supplementation increased alpha-tocopherol and BHA/BHT concentrations in meat and significantly (P less than 0.05) improved the oxidative stability of meat during refrigerated and frozen storage.

Influence of oxidised dietary oil and antioxidant supplementation on membrane-bound lipid stability in broiler meat.

1. The effects of oxidised oil, dietary alpha-tocopherol and BHA/BHT-supplementation on the fatty acid composition of mitochondrial, microsomal and soluble protein fractions of broiler muscles, and on their lability to metmyoglobin/hydrogen peroxide-catalysed peroxidation were investigated. 2. Oxidised oil in the broiler diets induced rapid oxidation of the membrane-bound lipids and decreased their stability towards metmyoglobin-hydrogen peroxide-catalysed peroxidation. 3. Supplementation of the broiler diets with alpha-tocopherol increased the alpha-tocopherol concentrations in the microsomal and soluble protein fractions of the dark meat as well as the soluble protein fraction of the white meat. This, in turn, stabilised the membrane-bound lipids against metmyoglobin/hydrogen peroxide-initiated peroxidative changes.

Improved oxidative stability of veal lipids and cholesterol through dietary vitamin E supplementation

The influence of dietary vitamin E supplementation on the α-tocopherol content of muscle membranes and on the resultant oxidative stability of veal was investigated. Daily supplementation of veal calves with 500 mg vitamin E in the form of α-tocopherol acetate for 12 weeks after birth increased muscle and membranal α-tocopherol concentrations approximately 6-fold over those of control animals. Oxidative stability of mitochondrial and microsomal lipids was enhanced by dietary supplementation as indicated by the results of an oxidative assay using hydrogen peroxide-activated metmyoglobin as the catalyst of oxidation. Muscle lipid and cholesterol stability was also improved by supplementation.

Nitrite stabilization of lipids in cured pork

Peroxidation studies indicated that phospholipids, microsomes and mitochondria from cured pork samples are less susceptible to metmyoglobin/hydrogen peroxide-catalyzed peroxidation than their counterparts from nitrite-free pork samples. The reaction of phospholipids and polyunsaturated fatty acid ethyl esters with dinitrogen trioxide increased their stability to peroxidative changes. Phospholipids from cured pork and those lipids reacted with dinitrogen trioxide were capable of nitrosating a secondary amine. These data, together with infrared analyses, indicate that nitrite or dinitrogen trioxide reacts with unsaturated lipids to form nitro-nitroso derivatives, thus stabilizing the lipids toward peroxidation changes. This mechanism can, in part, explain the antioxidant role of nitrite in cured meats.

Effect of dietary lipid and vitamin E supplementation on free radical production and lipid oxidation in porcine muscle microsomal fractions

Abstract The effect of dietary oxidised lipid and α-tocopherol on iron-induced free radical production and on lipid oxidation in porcine muscle was investigated. Free radical production and lipid oxidation were significantly lower in muscle microsomes from pigs fed an α-tocopherol-supplemented diet (200 mg α-tocopherol acetate/kg diet) compared to microsomes from pigs fed a control diet (10 mg α-tocopherol acetate/kg diet). The susceptibility of pork lipids to oxidise during refrigerated storage was also significantly lower in chops from pigs fed the α-tocopherol-supplemented diet. The inclusion of oxidised corn oil (peroxide value, 4·5 meq/kg diet) in diets did not have a significant effect on the oxidative stability of muscle lipids.

Effect of salt on myoglobin derivatives in the sarcoplasmic extract from pre- and post-rigor beef in the presence or absence of mitochondria and microsomes

The effect of salt and pH on the colour stability (oxymyoglobin) in the sarcoplasmic extract (SPE) prepared from pre- and post-rigor beef muscle was studied in the presence or absence of mitochondria and microsomes during 96 h at 4°C. The sarcoplasmic extract from the post-rigor meat (pH 5·4) or from the pre-rigor meat adjusted to pH 5·4 contained more oxymyoglobin (MbO(2)) than the pre- or post-rigor SPE maintained at pH 7·4. The presence or absence of mitochondria and microsomes in the SPE at pH 5·4 had little effect on the percentage of MbO(2). At pH 7·4, however, the percentage of MbO(2) decreased in the SPE in the presence of mitochondria, whereas the percentage of MetMb was lower in the presence of microsomes. The relative proportion of MbO(2) decreased and that of metmyoglobin (MetMb) increased with increasing salt concentration at low pH (more so in the absence of subcellular organelles) and with storage period in the SPE from both pre- and post-rigor meat. However, at pH 7·4, high levels of salt (2-4%) helped to maintain a high percentage of MbO(2) in SPE in the absence of subcellular organelles, especially the mitochondria. The first-order interactions of pH value × subcellular organelles (P < 0·01) and pH value × salt concentration (P < 0·01) accounted for about 55% of the total variation in the percentage of MbO(2) in the SPE. It is suggested that depressing microbial growth may be the operative mechanism by which added salt stabilizes the colour in pre-rigor minced meat rather than by enzymic effects of subcellular organelles.