Comprehensive analysis of oils and remaining solid matrices from supercritical fluid extraction of salmon side streams: Fatty acids, bioactive peptides, minerals, and heavy metals

Atlantic salmon (Salmo salar) side streams (head, backbone, and viscera) are nutrient-rich and offer potential for valorization. This study evaluates supercritical fluid extraction (SFE) and solvent extraction (SE) methods for recovering oils, fatty acids, bioactive peptides, minerals, heavy metals, and antioxidants from these byproducts. Both the oil and the remaining solid resulting from the extraction process were analyzed. SFE was more effective in extracting fatty acids from heads and backbones. However, SE yielded a higher peptide content, with SE backbone solids containing 281 peptides, and SE viscera and heads containing 220 peptides each. In contrast, SFE-derived solids had significantly fewer peptides: 9 in heads, 129 in backbones, and 130 in viscera. The identified peptides exhibit potential functional properties, including antioxidant, anti-inflammatory, antithrombotic, immunomodulating, anticancer, and hypolipidemic effects. Mineral and heavy metal content in all extracts met safety standards. SFE-derived matrices had the highest calcium levels (49.7 mg/g in heads, 24.2 mg/g in backbones) and lower heavy metal concentrations than SE. Arsenic, cadmium, mercury, and lead levels were 1.8 mg/kg, 1.8 μg/kg, 55.0 μg/kg, and 25.7 μg/kg, respectively, for SFE, compared to SE's higher values (e.g., 3.5 mg/kg for arsenic). Both methods produced extracts with promising antioxidant activity.