Seasonal variation in the biochemical composition of fish discards and its impact on the production of mince, protein hydrolysates, and oil

Fish discards and fish processing by-products represent valuable but variable resources. This study investigates the seasonal effects on the composition of representative discarded species, blue whiting, mackerel, and Atlantic horse mackerel, alongside their impact on the production and characterization of their protein hydrolysates and oils. Proximate analysis of specimens fractionated into mince, heads, viscera, skin and bones reveals significant seasonal differences in lipid and protein content, autumn samples generally exhibiting higher lipid levels. Mince consistently proves a high-protein, low-lipid fraction suitable for human consumption, while viscera from all species generally exceed heavy metal thresholds. Enzymatic hydrolysis of each fraction effectively yields protein hydrolysates, often increasing the essential amino acid proportion. The recovered oils demonstrate healthy characteristics, notably high omega-3 fatty acid content, which vary seasonally. These findings underscore the importance of seasonal assessment for optimizing the integral valorization of diverse fish discards into high-value compounds.