Abstract
Bone hydrolysates from bighead carp (Aristichthys nobilis) were prepared using Protamex and Alcalase with degrees of hydrolysis (DH) of 5%, 10% and 15%. The antioxidant activity of bone hydrolysates was evaluated in vitro and then the hydrolysates with better antioxidant activity were used to immerse bighead carp fillets through a vacuum impregnation process at concentrations of 1% and 2%. Among the six hydrolysates, fish bone hydrolyzed with Protamex at DH 10% exhibited the highest ability to scavenge 1, 1-diphenyl-2-picrylhydrazyl (DPPH) (88.79%), 2, 2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) (57.76%) and hydroxyl radicals (62.72%), as well as to chelate ferrous ions (91.46%). The hydrolysates effectively postponed freezing- and thawing-induced protein/lipid oxidation. Compared with the fillets without treatment, the impregnated fillets had higher sulfhydryl contents, greater Ca2+-ATPase activity, lower carbonyls and lower thiobarbituric acid-reactive substances (TBARS). Bone hydrolysates also have a positive effect on the texture and water-holding ability of freeze-thawed fish fillets. Fish bone hydrolysates of Protamex could serve as potential antioxidants to preserve fish fillets.
Highlights
Frozen storage is a common method for the long-term preservation of aquatic products
The antioxidant activity of protein hydrolysates is closely associated with molecular weight (MW) [30]
Compared to those macromolecular peptides, the peptides containing fewer than 10 amino acid residues usually had higher antioxidant activities [1]
Summary
Frozen storage is a common method for the long-term preservation of aquatic products. Microbial growth and endogenous enzyme activity can be effectively inhibited at low temperature, but protein/lipid oxidation still occurs [1], causing a deterioration in food quality, discoloration and protein denaturation, especially in conditions of temperature fluctuation or prolonged frozen storage [2,3]. During the fish filleting process, about 70% of the fish becomes solid by-products with low economic value, such as fish skin, bones, scales, heads and viscera [7]. They contain high-quality protein and ought to be further exploited. The hydrolysates that are obtained, which usually contain lots of low molecular weight peptides, usually present more specific bioactivities than the native collagen/gelatin, such as antioxidant, antibacterial, dipeptidyl peptidase IV (DPP-IV) and angiotensin-converting enzyme (ACE)
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