Analytical Characterization and Nutritional Potential of Blue Whiting Muscle and Hydrolyzed By-products as a Source of Antioxidant Peptides

Fish consumption is rapidly increasing worldwide, generating significant by-products and waste that offer opportunities for reuse as food, cosmetic, or pharmaceutical ingredients aimed at a sustainable economy. This study evaluated the effect of simulated gastrointestinal digestion (GID) on the generation of antioxidant peptides from blue whiting muscle as well as from by-products hydrolysates obtained by alcalase hydrolysis and ultrasound-assisted alcalase hydrolysis. A comprehensive peptide profile was obtained by nano- or ultra-high-performance liquid chromatography coupled to mass spectrometry, identifying 1246 medium- and 415 short-sized peptides. In this context, GID led to a significant reduction in the number of identified medium-sized peptides in all samples. Concurrently, the quantity of identified short peptides increased in the digested muscle, whereas it remained largely unchanged in the by-product hydrolysates. Peptides containing proline, aspartate, histidine, tryptophan, or glycine residues showed high resistance to GID, and in silico analyses predicted 36 short-sized sequences as bioactives. Results of in vitro assays showed that antioxidant activity generally increased after GID when measured by ABTS radical-scavenging capacity and oxygen radical absorbance capacity assays, whereas it decreased in DPPH free radical–scavenging and ferric-reducing antioxidant power assays. These findings underline the antioxidant potential of peptides derived from both blue whiting muscle and by-products, which could be valorised as a sustainable source of functional ingredients, promoting circular economy and reducing waste in aquaculture.