Sea bream bones and scales as a source of gelatin and ACE inhibitory peptides

- Sea bream scales and bones were used as sources of gelatin.
- Scales gelatin showed the highest gel strength and viscoelastic properties.
- The pretreatment of bones with Alcalase or HCl hardly modified the resulting gelatins.
- The use of HCl in the pretreatment of bones increased the removal of minerals.
- Scale gelatin may be a promising source of peptides with high ACE-inhibitory activity.

Sea bream scales and bones were used as sources of gelatin. Scales gave a higher gelatin yield than bones pretreated with HCl or Alcalase. Demineralization with EDTA was effective especially in the case of scale gelatin that showed the lowest ash content. The pretreatment of bones with HCl led to an increase in the removal of minerals. The gel strength and viscoelastic properties of sea bream scale gelatins were higher than those of bone gelatins, and only slight differences were found between gelatin extracted from bones pretreated with HCl or Alcalase, although the amino acid profile was similar in the three gelatins. The gel strength of scale gelatins was higher than that of a commercial bovine gelatin used for comparative purpose (Bloom 200-220). When the scales gelatin was hydrolyzed with Esperase, a high ACE-inhibitory activity was found in the peptide fraction below 3 kDa, and the amount of this peptide fraction required to inhibit 50% of the ACE activity (IC50) was around 60 μg/mL.