Beyond processing waste: Extraction of oil from Atlantic salmon (Salmo salar) by-products using immobilized Alcalase on chitosan-coated magnetic nanoparticles

Atlantic salmon (Salmon salar) aquaculture has been fully developed on a large scale worldwide. Currently in the Atlantic salmon processing industry, 40–50% of the fish body ends up as by-products, which contain a variety of nutrients and are mainly processed into functional ingredients for premium pet food and animal feed. With the global increase of interest in nutritional diets and supplements, more research has been performed for the valorization of salmon by-products into value-added food products for human consumption. In the present study, an immobilized protease was used for hydrolysis of Atlantic salmon by-products to extract salmon oil. Alcalase was immobilized on chitosan-coated iron (II, III) oxide nanoparticles via glutaraldehyde crosslinking. The immobilized Alcalase was characterized using Fourier transform infrared spectroscopy and transmission electron microscope. The optimum pH and temperature range for the immobilized Alcalase were determined as 8 and 55–65 °C, respectively. The salmon oil extraction process using the immobilized Alcalase was optimized through a factorial design, and the highest oil yield of 20.55% (88.30% recovery) was obtained from 1 h of hydrolysis at 65 °C. The oil recovery using the immobilized Alcalase was comparable to the use of free Alcalase. The low levels of oxidation and hydrolysis indicated the high quality of the extracted oil, which is promising to be processed into high-value products such as nutraceuticals and pharmaceuticals. The immobilized Alcalase was collected using a magnet and reused at least three batches without a significant decrease in oil yield, indicating its potential for effective and consecutive oil extraction from salmon by-products. The present study would promote the production of value chain products from unutilized Atlantic salmon resources and achieve sustainable development of the blue economy.