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ABSTRACT
Grass carp skin pieces were homogenized in water and hydrolyzed by Alcalase®, collagenase, proteinase K, and/or trypsin at their optimum conditions. Samples were taken at various degrees of hydrolysis and were evaluated for antioxidant, antimicrobial, and angiotensin-converting enzyme inhibitory activities. Alcalase and collagenase completely hydrolyzed the skin with different rates, and released peptides with antioxidant and angiotensin-converting enzyme-inhibitory activity. These activities increased linearly with increasing degrees of hydrolysis. Subsequent incubation of the collagenase hydrolysates with trypsin slightly increased the antioxidant activity. Proteinase K, although only partially hydrolyzing the skin, also catalyzed the release of peptides with antioxidant and angiotensin-converting enzyme-inhibitory activities. These results show that skin by-products from grass carp can be a source of bioactive peptides produced by a one-step reaction. Such hydrolysates may be applied in food products to prolong shelf life and provide beneficial effects on blood pressure.
Acknowledgments
The authors would like to thank the Huzhou Nanxun Xinya Produce Company, Zhejiang, China, for providing the fish samples. Yuhao Zhang, Anders H. Karlsson, Henriette Erichsen, Kirsten Sjøstrøm, and Finn K. Vogensen at the Department of Food Science, University of Copenhagen, are appreciated for their help with experimental work and data analysis, and Colin Ray from the same department is thanked for proofreading of the English language.
Funding
The financial support from the Danish Strategic Research Council through the NOVENIA project is gratefully acknowledged.