63-6 |
|
M. A. DETTMANN and M. P. Richards. Dept. of Animal Sciences, Univ. of Wisconsin, Madison, Muscle Biology & Meat Science Lab., 1805 Linden Dr. W., Madison, WI 53706 Lipid oxidation is a major cause of quality deterioration in muscle foods. Both hemoglobin and myoglobin are potential catalysts of lipid oxidation in muscle foods, yet little is known about their relative efficacy in stimulating lipid oxidation processes. This work was carried out to examine properties of rainbow trout hemoglobin (Hb) and myoglobin (Mb) and their ability to promote lipid oxidation. Hemolysates were prepared from lysed erythrocytes of adult fish. Anodic and cathodic trout Hb were isolated from hemolysates by anion exchange chromatography. Rainbow trout Mb was extracted by ammonium sulfate precipitation of cardiac tissue homogenates. Crude Mb was purified by gel filtration and anion exchange chromatography. Oxygenation and autoxidation of Hb and Mb solutions were examined spectrophotometrically at pH 6.3 and 4°C. The sperm whale mutant apomyoglobin (H64Y) with characteristic peak absorbance at 600 nm upon heme binding was utilized to examine heme dissociation from native proteins. Lipid oxidation was assessed by thiobarbituric acid reactive substances (TBARS) in washed cod exposed to the heme proteins of interest. Trout Mb exhibited no Bohr or Root effects, maintaining high oxygen affinity at reduced pH (pH 6.3). Anodic Hb had low oxygen affinity at pH 6.3. Mb autoxidized more rapidly compared to anodic Hb. However, Mb was a weaker catalyst of lipid oxidation than anodic Hb. Heme dissociation rates were higher in anodic Hb compared to Mb. Cathodic Hb had higher oxygen affinity, slower autoxidation rate, less heme dissociation and was a poorer catalyst of lipid oxidation compared to anodic Hb. These studies suggest that Hb has a greater propensity than Mb to stimulate lipid oxidation in trout muscle. Further, heme dissociation appears to be part of the mechanism by which heme proteins promote lipid oxidation. Somewhat surprisingly, trout Mb lost its desirable red color faster than Hb.
Session 63, Aquatic Food Products: Quality, processing, antioxidants and surimi
|