Fish scales and bones as nutraceutical resources

A 2025 open-access review by Jeyachandran and Aman, published in Bioresources and Bioprocessing, provides a comprehensive evaluation of the biochemical composition of fish scales and bones, the extraction and purification technologies available for recovering their principal biomolecules, their functional properties, and the challenges that currently obstruct their large-scale commercialisation as nutraceutical ingredients.

The review is situated within a broader body of scholarship on marine by-product valorisation (Coppola et al., 2021; Waqar et al., 2025) and contributes to a field of growing strategic importance as the seafood processing industry confronts mounting environmental and economic pressures.

Methodology

The study was conducted as a structured narrative review of peer-reviewed literature, drawing on sources identified via established academic databases. The authors evaluated evidence relating to the biochemical composition of fish scales and bones, extraction and purification protocols for collagen and functional proteins, characterisation methodologies, documented bioactivities, nutraceutical and cosmetic applications, and constraints on industrial scale-up.

Analytical techniques discussed include SDS-PAGE for molecular weight distribution and purity assessment, Fourier-transform infrared (FTIR) spectroscopy for structural characterisation of the triple-helical collagen backbone, circular dichroism (CD) spectroscopy for secondary structure verification, and differential scanning calorimetry (DSC) for measuring thermal stability — the latter being a reliable proxy for product quality and shelf-life potential.

These methods, applied in combination, provide a multidimensional picture of collagen integrity following extraction and purification.

Biochemical composition

Fish scales are composed predominantly of type I collagen and hydroxyapatite, the two structural constituents that confer mechanical resilience and rigidity to the tissue. Quantitatively, bones and scales typically contain 30%–40% of their dry mass as an organic collagen matrix, with the remaining 60%–70% constituted by hydroxyapatite minerals — a calcium phosphate structure that has independent applications in bone tissue engineering and biomaterial science.

Beyond collagen, both tissue fractions are rich in bioactive peptides and proteins with demonstrated antioxidant, anti-inflammatory, antimicrobial, and antihypertensive properties (Jeyachandran & Aman, 2025). Species-specific variability is a recurrent complication: the amino acid profile and thermal resistance of collagen differ meaningfully between cold-water species such as Atlantic cod and salmon and tropical species such as tilapia and catfish, with collagen extractability further influenced by the age of the fish, seasonal feeding patterns, and post-harvest processing conditions. Younger fish generally yield more extractable collagen owing to lower cross-linking density, while the collagen networks in older fish, though less bioavailable, exhibit superior structural strength.

Extraction and purification technologies

Conventional extraction of acid-soluble collagen (ASC) using acetic, lactic, or citric acids has historically been the most widely employed approach, typically yielding 10%–15% collagen whilst preserving the triple-helix structure. Pepsin-soluble collagen (PSC) extraction, which employs proteolytic enzymes to cleave the non-helical telopeptide regions, achieves higher yields of 20%–30% and improved bioactivity, including antioxidant and antihypertensive properties, while substantially reducing chemical waste relative to acid-only methods.

More recent innovations in green extraction— specifically ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) — have demonstrated yields comparable to or exceeding enzymatic methods (25%–35%) whilst dramatically reducing processing times from hours or days to minutes, and with lower solvent consumption.

Supercritical fluid extraction (SFE), employing CO₂ as a non-toxic solvent, achieves very high purity with excellent preservation of molecular integrity, though its high equipment costs and process complexity continue to limit widespread adoption. The review notes that immobilised enzyme systems and synergistic ultrasound-enzyme combinations represent a particularly promising direction, enhancing enzyme reusability and extraction efficiency whilst maintaining product quality.

Bioactive properties and health applications

The health-relevant properties attributed to fish scale and bone-derived compounds span a remarkably broad spectrum:

• antioxidant peptides derived from fish collagen hydrolysates have been shown in experimental studies to exhibit radical-scavenging and metal-chelation activities comparable to or exceeding those of vitamins C and E;

• ACE-inhibitory peptides, characterised by short amino acid sequences with hydrophobic and positively charged residues, demonstrate blood pressure-lowering capacity in preclinical models and are of interest as nutraceutical alternatives to pharmacological antihypertensives;

• anti-inflammatory peptides suppress the secretion of pro-inflammatory cytokines, including TNF-α, IL-6, and COX-2, suggesting potential utility in the management of arthritis and other chronic inflammatory conditions.

Clinical evidence reviewed by Jeyachandran and Aman (2025) indicates that:

• daily supplementation with 10 g of fish collagen peptides for 8–12 weeks improves skin hydration, elasticity, and wrinkle reduction in women aged 35–55;

• supplementation for 12 months with 5 g of collagen peptides combined with calcium and vitamin D has been associated with increased bone mineral density in postmenopausal women;

• antidiabetic activities, mediated through DPP-IV and alpha-amylase inhibition, and anti-osteoporotic effects through promotion of osteoblast activity and bone matrix reinforcement, further illustrate the breadth of documented bioactivities (Jeyachandran & Aman, 2025; Waqar et al., 2025).

Challenges and barriers to industrial translation

The gap between laboratory-scale promise and commercial viability remains considerable:

• raw material variability — arising from species diversity, geographic origin, seasonality, diet, and post-harvest treatment — introduces inconsistency in collagen content and peptide profiles that complicates process standardisation and quality assurance;

• enzyme costs remain a significant economic constraint on pepsin-based and advanced enzymatic approaches, while energy-intensive processes such as UAE, MAE, and SFE require careful optimisation before they can be cost-effectively scaled to industrial volumes.

From a regulatory standpoint, the legal landscape governing nutraceutical claims for marine collagen products is highly fragmented internationally: requirements for allergen labelling, contaminant limits — particularly heavy metals and persistent organic pollutants — and health claim substantiation differ markedly between jurisdictions, creating barriers to global market entry.

Bioavailability of orally administered peptides presents a further challenge, as enzymatic degradation during gastrointestinal transit can substantially reduce systemic absorption. Hydrolysates also frequently exhibit bitter taste profiles that limit consumer acceptability, necessitating technological interventions at the formulation stage (Jeyachandran & Aman, 2025).

Future directions and conclusions

The review identifies a practical roadmap for overcoming the principal bottlenecks. In the domain of process technology, continuous-flow bioreactors, enzyme immobilisation strategies, integrated biorefinery models — in which collagen, lipids, chitin, and minerals are co-extracted from the same biomass — and the adoption of deep eutectic solvents (DES) and subcritical water extraction (SWE) are highlighted as promising avenues for improving economic feasibility.

In terms of delivery systems, nanoencapsulation approaches — including nanoliposomes, polymeric nanoparticles, and nanoemulsions — have demonstrated capacity to protect peptide bioactivity, improve oral stability, mask bitter taste, and enhance consumer acceptability. For clinical translation, Jeyachandran and Aman (2025) call for the prioritisation of standardised raw material sourcing, pilot-scale continuous processing trials, systematic screening of nanocarrier formulations, and early regulatory mapping supported by toxicological and pharmacokinetic data.

The authors also identify synergistic formulation — combining fish collagen and peptides with other marine bioactives such as fucoidan, omega-3 fatty acids, and chitosan — as a frontier deserving active investigation. Overall, the study makes a compelling case that fish scales and bones, long treated as waste, constitute an abundant, sustainable, and scientifically substantiated feedstock for next-generation nutraceuticals, provided that the field addresses scalability, regulatory harmonisation, and bioavailability challenges in a coordinated manner.

#EcoeFISHent

#Wasteless

Dario Dongo