Valorisation of fish scales and bones: a sustainable source of bioactive proteins and collagen for nutraceuticals.

Fish scales and bones, traditionally regarded as low-value seafood by-products, represent abundant and sustainable sources of collagen and bioactive proteins with high nutraceutical potential. These tissues typically contain 30-40% organic collagen matrix and 60-70% hydroxyapatite minerals, making them rich substrates for recovery. Advances in green and enzymatic extraction methods now achieve collagen yields of up to 25-35%, with ultrasound- and microwave-assisted extraction reducing processing times from days to minutes while preserving the triple-helix structure and bioactivity. Enzymatically derived peptides demonstrate potent health-promoting effects, with antioxidant capacities comparable to or exceeding vitamins C and E, ACE-inhibitory peptides lowering blood pressure in preclinical models, and clinical trials showing that daily supplementation with 10 g fish collagen peptides for 8-12 weeks improves skin hydration, elasticity, wrinkle reduction, and reduces osteoarthritis-related joint pain. These marine biomolecules, when delivered through advanced nanocarrier systems such as nanoliposomes and nanoemulsions, exhibit enhanced bioavailability, stability, and consumer acceptability. Beyond health benefits, valorisation of fish by-products supports environmental sustainability by diverting waste and contributing to the circular bioeconomy. Despite challenges in scalability, regulatory compliance, and standardization, ongoing technological innovations position fish scales and bones as promising raw materials for next-generation nutraceuticals.