44-8 |
Evidence of deoxyhemoglobin-mediated lipid oxidation in washed fish muscle |
M. P. RICHARDS1, H. Østdal2, and H. J. Andersen2. (1) Animal Science-Food Science, U. Wisconsin-Madison, Meat Science and Muscle Biology Lab, 1805 Linden Dr. W., Madison, WI 53706, (2) Animal Product Quality, Danish Institute of Agricultural Sciences, Research Center Foulum, Tjele, DK-8830, Denmark Lipid oxidation is a major cause of quality deterioration in fish muscle. The off-odors and off-flavors that result from lipid oxidation lower the quality and thus shorten the shelf-life of the muscle. Hemoglobin is a likely catalyst of lipid oxidation in fish muscle. A better understanding of how hemoglobin promotes lipid oxidation in fish muscle could lead to quality improvements. The objective of these studies was to determine the effect of deoxyhemoglobin on rates of lipid oxidation. Trout hemoglobins are appropriate to study the effect of deoxyhemoglobin since the anodic hemoglobins of trout bind oxygen poorly at reduced pH while the cathodic hemoglobins bind oxygen independent of pH. Anodic and cathodic hemoglobins were isolated using anion exchange chromatography. Hemoglobin oxygenation was assessed by spectral changes in the soret band and visible range. Thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides were used to assess development of lipid oxidation during 2°C storage. The lipid substrate used was washed cod muscle. At pH 6.3, anodic hemoglobins were much less oxygenated than cathodic hemoglobins in air atmospheres. Likewise, lipid oxidation developed more rapidly when anodic hemoglobins were added to washed cod at pH 6.3 compared to cathodic hemoglobins. ATP was found to lower oxygenation of anodic hemoglobins at pH 7.2. ATP also accelerated the rate of lipid oxidation induced by anodic hemoglobins. The rate of lipid oxidation was less at pH 7.4 compared to pH 6.3 regardless of hemoglobin type. These studies strongly suggests that deoxyhemoglobin promotes lipid oxidation in trout muscle more rapidly than oxyhemoglobin. Deoxyhemoglobin can promote lipid oxidation through its ability to accelerate formation of hemoglobin species at higher oxidation states or due to better exposure of the catalytic heme group to the micro-enviornment.
Session 44, Seafood Technology: Safety
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