Separation of Membranes from Acid-Solubilized Fish Muscle Proteins with the Aid of Calcium Ions and Organic Acids

Abstract

Calcium chloride, and to a lesser extent MgCl2, aided in the separation of membranes by centrifugation from cod (Gadus morhua) muscle homogenates solubilized at pH 3 in the presence of citric acid or malic acid but not lactic acid. Adding citric acid and Ca2+ before solubilizing the cod muscle homogenates was needed for the effect. At 1 mM citric acid, 70-80% of the phospholipid and 25-30% of the protein were removed at 10 mM Ca2+. At 8 mM Ca2+, citric acid showed an optimal effect on phospholipid removal at 5 mM with 90% of the phospholipid and 35% of the protein removed. The treatment with citric acid and Ca2+ was also effective in separating the membrane from solubilized herring (Clupea harengus) muscle homogenate. Ca2+ and citric acid might exert their influence by disconnecting linkages between membranes and cytoskeletal proteins.

Functional and nutritional characteristics of proteins and lipids recovered by isoelectric processing of fish by-products and low-value fish: A review

“…Lipid recovery should be investigated more thoroughly because of fish lipids' nutritional benefits and hence, higher potential value than the recovered proteins. It has been demonstrated that ISP allows efficient recovery of fish lipids (Liang & Hultin, 2005a, 2005b. The pH during solubilisation of fish muscle proteins generally does not affect the composition of x-3 or x-6 PUFA, and consequently, the x-3/ x-6 ratio (Chen et al, , 2009Taskaya, Chen, Beamer, Tou, & Jaczynski, 2009c).…”

Effect of pretreatment on lipid oxidation and fishy odour development in protein hydrolysates from the muscle of Indian mackerel

“…Membranes were then removed from the W sample by treatment with Ca 2+ and citric acid according to the method of Liang and Hultin (2005) with a slight modification. The W sample was homogenised with nine volumes of cold 8 mmol/l CaCl 2 solution in the presence of 5 mmol/l citric acid at a speed of 11,000 rpm for 2 min.…”

“…Membrane bound phospholipids are believed to be a key substrate for lipid oxidation due to their highly unsaturated fatty acid composition. In addition, membranes have a large surface area to contact pro-oxidants in the aqueous phase of the cell, and their lipids are located near the site of electrons leaked from the electron transport process (Liang & Hultin, 2005). Ca 2+ as well as citric acid used for membrane removal might interact with those components, especially membrane lipids, thereby providing the charge or polarity to those components.…”

“…Additionally, Ca 2+ could interact with the polar head of phospholipid to form a calciumphospholipid complex. The membranes released from the cytoskeletal proteins might aggregate to a large particle as induced by Ca 2+ addition and sediment by centrifugation (Liang & Hultin, 2005). Hrynets et al (2011) reported that addition of 6 or 8 mmol/l of citric acid resulted in substaintial removal of lipid and pigments from mechanically separated turkey meat.…”

“…Furthermore, phospholipid membranes are believed to be the key substrate for lipid oxidation due to their highly unsaturated fatty acid composition (Liang & Hultin, 2005). Contamination of pro-oxidants and oxidised lipids in mince can have a great impact on functionality and antioxidative properties of protein hydrolysates (Raghavan & Kristinsson, 2008a).…”