The Physical And Chemical Properties Of Tuna Peptides And Their Self-assembly With Sodium Alginate

Fish processing by-products(skin,viscera,bones,etc.)are usually considered as low-value wastes,which have not been rationally utilized for a long time.Therefore,how to use these by-product wastes to produce high value-added products has become one of the hot issues in the field of research.In addition,polysaccharide polypeptide hydrogels have great potential in the field of biomedicine because of their good biocompatibility,biological function and biodegradability.In this paper,the chemical constituents of the by-products of yellowfin tuna processing were studied,and the physicochemical properties and antioxidant properties of the enzymatic hydrolyzed polypeptides were determined.Based on this,self-assembly and gelation properties of the yellowfin tuna polypeptide and polysaccharide(alginate)were self assembled,and the structural characteristics of gelation complex / gel fiber were studied.The main results are as follows:(1)The byproducts of yellowfin tuna contain 74.45% water,22.36% protein,4% fat and 1.91% ash.They are rich in essential amino acids and fatty acids and have high nutritional value.The degree of hydrolysis of by-product reached 28% after 2 hours of enzymatic hydrolysis,and the molecular weight of polypeptide was mainly concentrated below 5 kDa.(2)Polypeptides from yellowfin tuna exhibit differentiated antioxidant activity.In conclusion,compared with tuna polypeptide hydrolyzed at different time,when hydrolyzed for 20 minutes,the antioxidant activity of tuna polypeptide was the strongest,and its chelating metal ability and linoleic acid autoxidation inhibition ability were stronger than traditional antioxidants.Yellow fin tuna polypeptides also exhibit good antioxidant activity in terms of reducing capacity,DPPH radical scavenging capacity and superoxide anion scavenging capacity.(3)Compared with tuna polypeptide,the emulsifying,emulsifying,foaming and foaming stability of polypeptide/sodium alginate self-assembled complexes were significantly improved,the surface charge increased,and the surface hydrophobicity decreased.The self-assembled complexes were observed by field emission scanning electron microscopy.Sodium alginate was crosslinked with polypeptide to form network structure.(4)Polypeptide/sodium alginate and calcium chloride can form microgel fibers after being treated by a Vortex Fluid Device(VFD).The structure of the microgel fibers was characterized by optical microscopy and field emission scanning electron microscopy.It was found that VFD could effectively disperse and thin the hydrogel into microgel fibers,and keep the structure of the microgel fibers stable at low rotating speed.The prepared polypeptide/calcium alginate microgel fibers have strong acid resistance,and their structure has not changed significantly even at pH=3.