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Gisborne, Australia

Ahmed Z.,Victoria University of Melbourne | Donkor O.,Victoria University of Melbourne | Street W.A.,Geelong Food Co products Cluster | Vasiljevic T.,Victoria University of Melbourne
Food Chemistry | Year: 2013

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. © 2013 Elsevier Ltd. All rights reserved.

Ahmed Z.,Victoria University of Melbourne | Donkor O.N.,Victoria University of Melbourne | Street W.A.,Geelong Food Co products Cluster | Vasiljevic T.,Victoria University of Melbourne
Journal of Food Science | Year: 2013

Storage conditions may influence the hydrolytic activity of endogenous muscle enzymes postmortem, rate of autolysis of myofibrillar proteins, and biological properties of hydrolyzed end products. This study investigated the effect of ionic strength, pH, and temperature on the activity of endogenous calpain-like, cathepsins B and B+L measured in crude extract obtained from deepwater flathead, silver warehou, ribaldo, and ribbonfish muscles. Activity of calpain-like enzymes in 3 examined species was significantly higher at pH 6.5 than pH 6.0 or 5.5. Raising the reaction temperature increased (P < 0.05) calpain-like activity in ribaldo. Endogenous activity of cathepsin B in ribbonfish and silver warehou declined significantly with increasing ionic strength at pH 6.5 to 6.0. The obtained results will further expand our understanding of the impact that postmortem storage conditions have on the activity of endogenous fish proteases with respect to quality and bioactivity of fish proteins and potentially diversify utilization of underutilized fish species. © 2013 Institute of Food Technologists®.

Manikkam V.,Victoria University of Melbourne | Mathai M.L.,Victoria University of Melbourne | Street W.A.,Geelong Food Co products Cluster | Donkor O.N.,Victoria University of Melbourne | Vasiljevic T.,Victoria University of Melbourne
International Food Research Journal | Year: 2016

Fish waste, such as scales, is a rich source of proteins, which can be applied in various commercial applications. Enzymatic hydrolysis for example simulated gastrointestinal digestion (SGID) can release physiologically active peptides with the potential to benefit consumers' health. Powdered (PH) and agglomerated (AH) hydrolysates prepared from fish scales-derived collagen were investigated for their physiological and biofunctional properties. Having a higher protein and moisture content, PH showed greater solubility and digestibility than AH. In vitro SGID significantly impacted on the studied inhibitory activities. The released peptides (RP) of PH after completed digestion, exhibited higher angiotensin converting enzyme inhibitory (ACE-I) activity (73.65%) compared to AH. Both preparations showed similar trypsin inhibitory (TI) activities, 44.33% and 47.11% respectively. In contrast, the antioxidant activities of the hydrolysates were very low upon SGID. Physicochemical properties of these preparations apparently affected their in vitro physiological properties, which were further modulated through SGID.

Ahmed Z.,Victoria University of Melbourne | Donkor O.,Victoria University of Melbourne | Street W.A.,Geelong Food Co products Cluster | Vasiljevic T.,Victoria University of Melbourne
Trends in Food Science and Technology | Year: 2015

Proteolytic activation of endogenous muscle proteases, calpains and cathepsins, contributes to autolysis of fish myofibrils and concomitant softening of fillets during post-mortem storage. Calpains activity causes limited hydrolysis of myofibrils during initial days of post-mortem storage, whereas cathepsins in addition to proteolysis of major myofibrillar and associated proteins have the capacity to breakdown actin and myosin at later stages of post-mortem storage. Proteolysis of fish myofibrils post-mortem releases polypeptides and oligopeptides, some of which may demonstrate potential bioactive properties. © 2015 Elsevier Ltd.

Nurdiani R.,Victoria University of Melbourne | Nurdiani R.,Brawijaya University | Dissanayake M.,Victoria University of Melbourne | Street W.E.,Geelong Food Co products Cluster | And 3 more authors.
International Journal of Food Science and Technology | Year: 2015

Fish by-products are considered low value and discarded. With proper handling and processing, fish by-products may provide high nutritional value to consumers. This study aimed at establishing compositional differences in valuable compounds from fish by-products of selected species, including Salmon, Flathead, Silver warehou and Barramundi. Simple extraction methods were employed, and obtained fractions were analysed for their chemical and physical properties. The chemical composition of four fish species differed significantly (P < 0.05) with the protein content ranging from 14.7 ± 0.09 to 16.8 ± 0.41%. Adjusting pH to 2.5 yielded two times more of extracted oil than at pH 4.5. Salmon and Barramundi oils contained high amounts of monounsaturated fatty acids (MUFAs) (39-50%), while Silver warehou and Flathead oils contained 46-49% of saturated fatty acids (SFAs). The particle size of the protein fractions was small, ranging from 126.9 to 489.5 nm. Molecular weight of extracted proteins was fish species dependant - Silver warehou and Barramundi samples contained proteins of 250, 120 and 100 kDa, while these bands were absent from Salmon and Flathead samples. The data obtained indicate that extracted fractions from fish by-products likely have high nutritional value and could find a potential use in food formulations. © 2015 Institute of Food Science and Technology.

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