Texture is one of the most important quality parameters of fish muscle which impacts
consumer’s acceptance, the market value and the suitability of fish for processing and
preservation. Textural changes are rapid in fish muscle leading to unfavourable quality changes
such as muscle softening and fillet gaping. Rapid softening of flesh may be one of the main
reasons for underutilization of a wide range of bycatch and discarded fishery species. High
proteolytic activity of endogenous muscle proteases, calpains and cathepsins, induces
myofibrillar breakdown involved in softening of fish during post-mortem storage. In addition,
post-mortem proteolysis of fish myofibrils by endogenous enzymes releases polypeptides and
oligopeptides, some of which may demonstrate potential bioactive properties. The scope of the
present research was to determine the major endogenous enzymes active in post-mortem fish
muscle and establish their impact on structural softening and the release of bioactive peptides
during storage of underutilized fish species.