8-5 |
Lipid: Protein interactions: A potential basis for lipid oxidation induced discoloration of foods |
L. C. FAUSTMAN, Dept. of Animal Science, Univ. of Connecticut, 3636 Horsebarn Rd., Ext. U-40, Storrs, CT 06269-4040 The maintenance of desirable quality of meat during acquisition, shipping and retail sale is critically important to its economic value. Our research effort has focused on the relationship between myoglobin oxidation and lipid oxidation in fresh meat products. We have characterized the impact and chemistry of the antioxidant a-tocopherol in these deteriorative processes in beef. Interestingly, the results of this work have confirmed a tight linkage between the processes of myoglobin oxidation and lipid oxidation. We are currently pursuing a more fundamental approach to determine the physico-chemical mechanism(s) responsible for this interaction. Recently we found that a,b monounsaturated aldehyde products of lipid oxidation enhance the oxidation rate of oxymyoglobin, and that the aldehyde, 4-hydroxynonenal (HNE), is especially reactive. Interestingly, preincubation of metmyoglobin (MetMb) with a,b monounsaturated aldehydes rendered the heme protein a poorer substrate for enzymatic MetMb reduction, and enhanced the prooxidant capacity of MetMb relative to controls in vitro (P<0.05). Saturated aldehyde products are relatively ineffective when compared to their unsaturated counterparts, and increasing the carbon chain length of the a,b monounsaturated aldehydes appears to increase their effectiveness. We have confirmed the presence of HNE:histidine adducts in horse heart myoglobin reacted with HNE by using a monoclonal antibody approach. Additionally, proteins adducted by HNE, malondialdehyde, and hexenal, heptenal, octenal and nonenal were detected in phosphatidylcholine liposomes, bovine liver microsomes, and beef by indirect ELISA using polyclonal antibodies developed in our laboratory. At present, we are attempting to identify the specific amino acid sites on myoglobin that are most susceptible to covalent attachment by a,b monounsaturated aldehydes and to assess how this modification alters protein structure and functionality.
Session 8, Oxidation in heterogenous foods and biological tissues: Impact on food quality and health
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