68-2

E. W. GRUNWALD, Meat Science and Muscle Biology Laboratory, Univ. of Wisconsin-Madison, 1805 Linden Drive West, Madison, WI 53706 and M. P. Richards, Dept. of Animal Sciences/Dept. of Food Science, Univ. of Wisconsin, Madison, 1805 Linden Dr. W., 272 Meat Science & Muscle Biology Lab., Madison, WI 53706.

Lipid oxidation reduces quality of muscle foods during storage. Myoglobin is a likely promoter of lipid oxidation in muscle foods. It has been suggested that heme promotes lipid oxidation in muscle foods. Substitution of amino acids at specific locations in myoglobin can be used to investigate structural interactions with heme in certain environments. This facilitates understanding of mechanisms through which myoglobin may promote lipid oxidation in muscle foods. The objectives were to examine influences of heme affinity and degradation on rates of lipid oxidation in washed cod muscle. Wild type, V68T, H97A, and H64Q/L29F mutants of sperm whale myoglobin were expressed in E. coli BL21(DE3) and purified by ammonium sulfate precipitation and ion exchange chromatography. Each myoglobin was mixed into washed cod muscle and stored on ice for 8 days. Lipid oxidation was monitored by measuring mmol TBARS/kg of muscle. Degradation of heme in wild type and H64Q/L29F was monitored in aqueous systems by a decrease at A₄₁₀. Loss of heme from H97A and V68T globins was monitored in aqueous systems by an increase at A₆₀₀. Day 4 TBARS values of 32.80 (wild type) and 1.37 (H64Q/L29F) demonstrate the superior pro–oxidant properties of wild type. A₄₁₀ values of 0.288 (wild type) and 0.119 (H64Q/L29F) suggest this is due to a resistance to heme degradation in wild type. TBARS value for V68T reached a maximum of 20.50 on day 8, while H97A achieved maximal oxidation (38.07) by day 3. Heme loss values suggest this is due to the lower affinity for heme of the H97A versus V68T globin. The affinity of myoglobin for heme and the stability of heme in certain environments appear to be significant components of the mechanism of lipid oxidation in muscle foods. Further investigation of these components will likely yield improved storage strategies for muscle foods.

Session 68, Muscle Foods: Biochemistry, color and non-meat ingredients
9:00 AM - 12:00 PM, Tuesday AM Room 396

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana