Proteolytic activities in fillets of selected underutilized Australian fish species.

The hydrolytic activity of major endogenous proteases, responsible for proteolysis of myofibrillar proteins during post-mortem storage, may be an indicator of the textural quality of fish which influences consumer purchasing behaviour and thus market value of the final product. Furthermore, it may also influence the type and bioactive properties of the peptides released during post-mortem proteolysis of myofibrillar proteins. This study compared the activities of cathepsins B, B+L, D, H and calpain-like enzymes in crude muscle extracted from 16 Australian underutilized fish species. Fish species had a significant effect on the activity of these enzymes with barracouta showing the highest cathepsins B, B+L, D and H activities. Activities of cathepsins B and B+L were higher than cathepsin H for all studied species. The more commercially important rock ling and tiger flathead demonstrated higher cathepsin B+L activity, whereas gemfish and eastern school whiting showed higher activity towards cathepsin B. Underutilized fish species showing higher endogenous protease activities may be suitable for fish sauce production, whereas those with lower protease activities for surimi processing.