Value added fish by-products - Nordic Innovation

Fish protein hydrolysates are rich in bioactive peptides, but they are less investigated than
peptides from other sources such as milk (Underland et al. 2009). Different raw material,
hydrolysis conditions, separation and isolation would influence the release and amount of
these peptides. The types of enzymes and degree of hydrolysis influence the properties of
bioactive peptides: short peptides (2-8 amino acids residues) have shown high ACE inhibiting
(reduction of high blood pressure) activity, while longer peptides (5-14 amino acids residues)
have shown good antioxidative properties in vitro (Thorkelsson et al. 2009). The amino acid
sequence effect also the ACE-inhabitation. Fish protein hydrolysates can also function as
immuno-stimulants, have anti-carcinogenic effects and anti-anaemia activity (Underland et al.
2009).
The hydrolysis process can lead to the production of various peptides bearing a structural
resemblance to hormones. These newly formed peptides can retain the biological properties of
the native protein, or can show new properties. The calcitonin-gene related peptide (CGRP) is
a 37-residue peptide widely distributed in the central nervous system and peripheral nerves.
Different biological functions have been described for CGRP, such as vasodilatation (Gupta et
al. 2006) and induction of satiety (Huges et al. 1984; Lenz et al. 1984). On the other hand,
different authors have reported the presence of gastrin/CCK-like molecules in protein
hydrolysates from fish rest raw materials (Cancre et al. 1999; Ravallec-Ple & Van
Wormhoudt 2003). These molecules are the only known members of the gastrin family in
humans, and could have a positive effect on food intake in humans and fish species in
aquaculture. Gastrin is a gastric hormone which stimulates postprandial gastric acid secretion
and epithelial cell proliferation. In humans there are two different gastrins, one with 17 and
one with 34 amino acids residues. Cholecystokinin (CCK) is a group of peptides which
controls the emptying of the gallbladder, as well as pancreatic enzyme secretion. It is also a
growth factor, and regulates intestinal motility, satiety signalling and the inhibition of gastric
acid secretion (Rehfeld et al. 2001). Both gastrin and CCK inhibit food intake and share a
common COOH-terminal pentapeptide amide that also includes the sequences essential for
biological activity.
2.4.1 Health advantages
Several beneficial health effects are linked to fish consumption in general but some of these
effects are suggested to be better by intake of FPH due to the high content of easily digestible
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