| The main edible part of sea cucumber is the body wall,in which the protein content is very high,and the collagen was up to 70%of crude protein.It could be speculated that the special changes of the elasticity and hardness of the body wall of the sea cucumber during heat treatment may be related to the changes of collagen and glycosaminoglycans.In this study,the pepsin-solubilized collagen(PSC)were extracted from fresh sea cucumber body wall,First,the thermal stability of collagen at different storage temperatures was studied by high performance liquid chromatography(HPLC)and electron spin resonance spectroscopy.Then,the physical and chemical properties of PSC and chondroitin sulfate(CS)mixed with different proportions were analyzed through infrared spectroscopy(IR),circular dichroism(CD),differential scanning calorimetry(DSC),scanning electron microscope(SEM),low field nuclear magnetic resonance(NMR),x-ray,rheometer(DHR),nanoparticle potentiometric analyzer.Finally,the distribution of collagen in the body wall of sea cucumber under different processing conditions was analyzed by infrared microscopy.Results of(HPLC)analysis showed that the main molecular weight of PSC of sea cucumber without heating was 300-130kDa,but the molecular weight less than 60kDa was in a low content.Under the condition of 37? storage 8h,the molecular weight peptides more than 140kDa nearly disappeared,and the molecular weight of less than 60kDa significantly increased,which indicated that the collagen has been obviously degraded.When PSC was added into the Fenton system,the degradation speed of collagen obviously accelerated,while the addition of EGCG could delay the degradation of collagen.Electron spin resonance spectroscopy results showed that hydroxy radical in sea cucumber PSC was very low and difficult to detect when unheated,when heated at 37?,the generation of hydroxy increased gradually;a large number of hydroxy signal was detected when added into Fenton system,after adding to EGCG,hydroxy signal became weak or disappeared.Based on the results above,it was concluded that the degradation of PSC is mainly related to the formation of hydroxy radical in the system.Differential scanning calorimetry analysis results showed that when added CS in sea cucumber PSC,mixture denaturation temperature became low with the increasing proportion of CS;rheometer test showed that the mixture viscosity decreased slightly;low field nuclear magnetic resonance showed that free water reduced and bound water increased in the mixture;nano particle size analyzer showed that potential of the mixture decreased and there was no regular change in particle;Fourier transform infrared detection found that the change of the mixture molecular structure of the order was amide ? band>amideIband>amide ?band>-CH2-group changes,the secondary structure of PSC in sea cucumber had obvious change when heated to 34?,when added CS,the change was found when heated to 32?;circular dichroism found,after adding to CS in the PSC,PSC characteristic peak appeared deviation at 197nm round,and the characteristic peak at 225nm gradually decreased,collagen three spiral changed.Scanning electron microscopy showed that the fibers became thicker,the molecular gap became smaller and part of polysaccharide were attached to the surface of PSC when PSC mixed with CS.X-ray diffraction results showed that PSC mixed with CS produced new diffraction peaks,which indicated that CS could reorganize the ordered high-level structure of PSC.Finally,In this paper,the changes of the distribution of collagen in the body wall of sea cucumber were studied by infrared microscopy,and through second derivative,overlapping peaks in spectra could be distinguished.when extracting characteristic peak through differential figure,the distribution of collagen components could be obtained.And the distribution of collagen in situ could be observed by principal component analysis. |
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