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Y. LIANG, Dept. of Food Science & Human Nutrition, Univ. of Florida, 130-B Aquatic Foods Pilot Plant, PO Box 110370, Gainesville, FL 32611-0370 and H. O. Hultin, Dept. of Food Science, Univ. of Massachusetts, Amherst, Marine Station, PO Box 7128, Gloucester, MA 01930. The phospholipids present in muscle cell membranes are susceptible to lipid oxidation and considered to be primary substrates for lipid oxidation compared with triacylglycerols. Separating membrane phospholipids from muscle proteins may significantly reduce lipid oxidation susceptibility of muscle foods. Recently, a new method has been developed to separate proteins from muscle tissues. The solubilization of muscle proteins in the procedure makes it possible to separate membrane phospholipids from muscle proteins by centrifugation. However, only limited amounts of membrane phospholipids could be separated by centrifugation at 4,000 g, a typical centrifugal force used in the food industry. The objective was to study the sedimentation behavior of membranes and look for practical methods to remove cellular membranes from solubilized muscle proteins at low g force. The sedimentation of membranes was first studied using the isolated membranes to avoid the interference of muscle proteins. The effect of Ca2+ (Mg2+) and citric acid on membrane sedimentation was studied with the muscle homogenate preparations. The results showed that in the absence of muscle proteins, isolated membranes could be easily sedimented at 4,000 g at pH 5 or below but not at pH 6 or higher. In the presence of muscle proteins, membrane phospholipids could not be sedimented solely by adjusting the pH to 3. Treatment with CaCl2 (MgCl2) and citric acid could remove up to 90% of the original phospholipids from muscle samples at 4,000 g. Some loss of muscle proteins occurred during membrane removal. The results showed that membrane phospholipids could be selectively removed from solubilized muscle proteins at low g force. The treatment with Ca2+ and citric acid might exert their influence by disconnecting linkages between membranes and cytoskeletal proteins and/or aiding in aggregation of the membranes.
Session 63, Aquatic Food Products: Quality, processing, antioxidants and surimi
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