| The extraction of collagen peptides from fish processing by-products not only achieves a high value use of the by-products,but also remedies the problems of infectious diseases and religious beliefs associated with collagen peptides of mammalian origin.In this paper,gelatin was extracted from pollock skin and bone after pretreatment,and the differences between the physicochemical properties of gelatin prepared from different raw materials were compared;collagen peptides from fish skin and fish bone were prepared by enzymatic digestion of gelatin by bioenzymatic technology,and their physicochemical properties were analysed,and structural analysis was carried out by chromatography,and the changes in the in vitro activity of collagen peptides from fish skin and fish bone before and after gastrointestinal simulated digestion were investigated to provide a theoretical basis and technical support for the comprehensive utilization of pollock processing by-products.The results of the study are as follows:(1)Extract gelatine from two different raw materials,pollock skin and fish bone,and investigate its physicochemical properties,molecular weight distribution and structural properties.The results of the study showed that the prepared gelatine had two electrophoretic bands,α and β,which are classical collagen structural composition;the UV-visible spectra showed that fish skin and fish bone gelatine had the strongest absorption peak at 280 nm;the Fourier transform infrared spectra showed that fish skin and fish bone gelatine had amide A band,amide B band,amide I band,amide II band and amide III band.The results of the functional properties study show that fish skin gelatine is better than fish bone gelatine in terms of foaming,emulsification and fat absorption,indicating that fish skin gelatine is more suitable for use in the food and cosmetic industries.(2)Using the hydrolysis degree and peptide yield as evaluation indexes,the optimal enzymes for the preparation of collagen peptides from gelatin were screened: flavour protease and alkaline protease,and the optimal enzymatic conditions were optimized by orthogonal test based on single-factor test: flavour protease feed to liquid ratio of 1:2 at35℃,p H 5.7 for 11 h;alkaline protease feed to liquid ratio of 1:40 at 55℃,p H 9.5 for 6 h.The enzymatic digestion of fish skin and fish bones was carried out with a combination of flavour protease and alkaline protease for 6 h.The degrees of hydrolysis were 80.75±0.09%and 70.34±0.18% respectively.(3)The physicochemical properties of fish skin and fish bone collagen peptides were determined and analysed.The results showed that both fish skin and fish bone collagen peptides had good solubility(>84%),emulsification and emulsion stability,oil absorption,moisture absorption and moisturizing properties under different p H conditions.The UV-visible spectral results showed that both fish skin and fish bone collagen peptides had the strongest absorption peaks at 270 nm;the Fourier transform infrared spectral results showed that fish skin and fish bone collagen peptides had N-H stretching vibrations,symmetric and antisymmetric stretching vibrations of C-H in CH: and CH:,C=O stretching vibrations of carbonyl groups and stretching vibrations of C-C and C-O.(4)In vitro efficacy evaluation of fish skin collagen peptide.The scavenging ability of fish skin collagen peptide for different free radicals was concentration-dependent,and the scavenging ability increased with increasing concentration,with good in vitro antioxidant effect.Among them,the scavenging rate of DPPH radical,ABTS radical,hydroxyl radical and superoxide anion radical reached the highest value of 59.43%,68.73%,71.22% and 49.54% at 1 mg/m L,and the total antioxidant capacity reached the maximum value of 94.33 mmol/g at 2 mg/m L;fish skin collagen peptide had some inhibitory effect on α-glucosidase.In addition,fish skin collagen peptide also had good inhibition of ACE enzyme activity,reaching a maximum value of 32.58% at a concentration of 2 mg/m L.After in vitro gastrointestinal digestion,the scavenging ability of fish skin collagen peptide for different free radicals was still concentration-dependent,and the scavenging ability increased with increasing concentration,with good in vitro antioxidant effect.Compared with before in vitro gastrointestinal digestion,the scavenging power of DPPH radical,ABTS radical,hydroxyl radical and superoxide anion radical decreased by 23.97%,52.34%,45.53% and 34.29%,respectively,and the total antioxidant capacity decreased by 38.21 mmol/g;the α-glucosidase inhibition decreased by 13.2%;ACE enzyme inhibition decreased by 14.13%.The total antioxidant capacity decreased by 38.21 mmol/g;α-glucosidase inhibition decreased by 13.2%;ACEase inhibition decreased by 14.13%.(5)In vitro efficacy evaluation of fish collagen peptide.The scavenging ability of fish bone collagen peptide for different free radicals was concentration-dependent,and the scavenging ability increased with the increase of concentration,with good in vitro antioxidant effect.Among them,the scavenging rate of DPPH radical,ABTS radical,hydroxyl radical and superoxide anion radical reached the highest value of 52.17%,54.26%,52.17% and 43.89% at 1 mg/m L,and the total antioxidant capacity reached the maximum value of 94.40 mmol/g at 2 mg/m L;fish bone collagen peptide had some inhibitory effect on α-glucosidase.Fish bone collagen peptide had some inhibitory effect on α-glucosidase,reaching a maximum value of 28.7% at a concentration of 2 mg/m L;fish bone collagen peptide also had better inhibitory effect on ACE enzyme activity,reaching a maximum value of 39.87% at a concentration of 2 mg/m L.After in vitro gastrointestinal digestion,the scavenging ability of fish bone collagen peptide for different free radicals was still concentration-dependent,and the scavenging ability increased with increasing concentration,with better in vitro antioxidant effect.Compared with before in vitro gastrointestinal digestion,the scavenging power of DPPH radical,ABTS radical,hydroxyl radical and superoxide anion radical decreased by 39.63%,45.32%,33.80% and34.33%,respectively,and the total antioxidant capacity decreased by 47.51 mmol/g;theα-glucosidase inhibition decreased by 15.3%;ACE enzyme inhibition decreased by25.75%.decreased by 25.75%.In summary,the collagen peptides from fish skin and fish bone produced by complex enzymatic digestion with flavoured proteases and alkaline proteases belong to type I collagen peptides,which have good in vitro antioxidant,inhibiting α-glucosidase and ACE enzyme activities.Therefore,the extraction of collagen peptides from processing by-products such as pollock skin and fish bones can provide a reference for the subsequent preparation of functional foods with antioxidant,hypoglycaemic and hypotensive activities. |
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