Preparation And Properties Of Collagen Peptide Chelate Zinc Complexes From Tilapia Skin

The most kind of freshwater cultured fish is Tilapia in China.Tilapia is favorited by the public,due to its low fat and full of variety of unsaturated fatty acids.With the development of the level of people's live,the demand of health foods for them was significantly increased,and the market demand had improved the acceleration of Tilapia industry.At the same time,a large number of by-products were generated during processing,such as fish skin,which can be used as the safe protein sources.To achieve the high value utilization of tilapia skin,the tilapia skin collagen peptide was used as material in this study,and chelated with zinc lactate to form peptide-zinc complex.Firstly,the effect of the molecular weight of collagen peptide on their zinc chelating capacity,and zinc bioaccessibility of peptide-zinc complexes in vitro digestion was investigated.Secondly,the peptide which had high zinc bioaccessibility in the above experiment,was used as the material,and the determination of production process conditions was optimized by orthogonal experiments.Lastly,the comparison of the characteristics of zinc sulfate-peptide complex and zinc lactatepeptide complex was evaluated.The main research results were as follows:1.Effect of molecular weight of Tilapia skin collagen peptide fractions on zincchelating capacity,and bioaccessibility of the zinc-peptide complexes in vitro digestionTo investigate the effect of the molecular weight of tilapia skin collagen peptide fractions on their zinc chelation capacity and the bioaccessibility of their zinc complexes,we evaluated the zinc-chelating ability of different molecular weight peptide fractions,the solubility,and the stability of the complexes during simulated in vitro digestion.According to the amino acid composition,different molecular weight peptide exhibited similar the content amino acid residues,respectively.Low molecular weight peptide(P1)with the more negative surface charges and variety of metal chelate amino acid residues exhibited a higher zinc-chelating ability.The highest solubility and the lowest release of zinc during peptic digestion for the P1-zinc complex and the zinc binding to P1 were retained at approximately 50% after peptic-pancreatic digestion.Fourier transform infrared spectroscopy indicated the primary involvement of the N-H group in all peptide-zinc complexes.This finding suggests that low molecular weight peptide with strong zinc chelation ability can be used as delivery agents to improve zinc bioaccessibility.2.The optimization preparation process and structure characteristic of peptide-zinc complexThe low molecular weight peptide P1 was taken as the sample,and the optimization experiment of preparing peptide zinc chelate was carried out.Single factor and orthogonal optimization experiments were used to determine the optimal conditions for peptide zinc chelate as follows: the reaction time,30 min;the reaction temperature,45 ?;p H,6;The mass ratio of peptide to zinc,1:1.Under this condition,the zinc-chelating capacity of peptide was 59.38±1.24%.The structure of zinc-peptide complex was characterized by Fourier transform infrared spectroscopy,UV analysis and scanning electron microscopy,and the results showed that the peptide and zinc lactate formed a stable nanostructure.3.The properties comparison of peptide-zinc sulfate and peptide-zinc lactate complexesUnder the optimal conditions,zinc sulfate and zinc lactate were used as zinc sources to prepare zinc sulfate peptide complex and zinc lactate peptide complex respectively.The structural characteristics,antioxidant properties and in vitro bioactivity of the two chelates were studied.The results showed that,compared with zinc sulfate peptide complex,zinc lactate peptide complex with stronger antioxidant properties but showed lower zinc chelating ability.Fourier transform infrared spectrum and ultraviolet scanning spectrum show that acid radical ions can affect the participation of C-O functional groups in peptide in chelating reaction.Furthermore,zinc release during peptic digestion for P-Zn-L which has the higher zinc solubility,and less than 50% of zinc bound in it after digestion of gastrointestinal tract.The results suggested that P-Zn-L with a granular structure reduced gastric stability and promote intestinal release,and zinc lactate,may have potential to as an alternative to zinc sulfate used in chelation.