Isolation of collagen from the skins of Baltic cod (Gadus morhua)

The aim of the investigations was to establish the optimum conditions for the isolation of odourless and colourless collagen from the skins of cod (Gadus morhua) by solvent extraction. It was established that, with the use of a one-stage, 24-h extraction of whole skins with acetic or citric acid at ratios of material to solvent of 1:6 and 1:4, respectively, about 20% of collagen was extracted. Using three consecutive 24-h extractions of whole skins with citric acid, 85% of collagen protein could be separated. The thermal solubility of collagen depends on the medium applied. About 85 and 15% of collagen contained in the skins were dissolved in 0.45 M NaCl solution and water, respectively, after 24 h incubation at 30 °C. The addition of 0.5% non-ionic detergent to all extracting solutions used in the purification procedure and the solubilisation of collagen in 0.5 M citric acid entirely prevented development of rancid off-odour for up to 50 days of storage of the product at 4 °C. Similar effects could be achieved at 4 and 20 °C, respectively, in the presence of 0.14% of aseptine M-14 in the collagen solution in citric acid.