Effect Of Different Heat Treatments On Preparation And Activity Of Polypeptide And Polysaccharide Of Sea Cucumber

Sea cucumbers are rich in nutrients and their unique autolytic properties lead to heat treatment being an essential and important tool in the processing of sea cucumbers.In this paper,sea cucumbers were subjected to heat treatment by atmosphere boiling for 30 min（APB30）,atmosphere boiling for 90 min（APB90）,high pressure steaming for 30 min（HPS30）and high pressure steaming for 90 min（HPS90）,and the unheated sea cucumber body wall（FS-Fresh sea cucumber）was used as the control to study the effects of different heat treatments on the preparation of sea cucumber peptides and polysaccharides and their antioxidant activities,the results were as follows:1.After heat treatment,the mass loss rates of the body wall of the four groups of sea cucumbers,APB30,APB90,HPS30 and HPS90,were 71.14%,75.42%,74.96%and 83.06%respectively.2.The chemical composition and antioxidant activity of the hydrolysates in the body wall of sea cucumber were affected by different heat treatment methods.The hydrolysis degree of FS group was the highest（32.98%）,followed by APB group（28.53%and 28.90%）,and HPS group was the lowest（19.26%and 24.44%）.All sea cucumber body wall enzymes had the highest relative protein content（49.83%～63.66%）,especially in the HPS90 group（63.66%）.The total amount of amino acids in the enzymatic digest of different sea cucumber body walls ranged from31.16 to 45.69 g/100g.After heat treatment,the content of essential amino acids and fresh amino acids increased.The highest glucose content（49.04%～62.20%）was found in the monosaccharide composition of the enzymatic digest of different sea cucumber body walls.After heat treatment,the relative content of mannose decreased and that of rock candy increased.The heavy mean molecular weights of FS,APB30,APB90,HPS30 and HPS90 were 2.098×10⁵,2.900×10⁵,6.254×10⁵,9.892×10⁴ and 3.786×10⁴ g/mol,respectively.After heat treatment,the molecular weight of the APB group increased and that of the HPS group decreased.The enzymatic decomposition of the body wall of different sea cucumbers has certain DPPH,ABTS and hydroxyl radical scavenging ability as well as iron reducing power and Fe²⁺binding ability,and the strength and weakness of the ability all gradually increase with increasing concentration.The effect of heat treatment on the antioxidant activity of sea cucumber body wall hydrolysates was different.After heat treatment,the scavenging ability of DPPH radicals was enhanced in all groups and weakened in all ABTS radicals（except APB90 group）;the scavenging ability of hydroxyl radicals was weakened in APB group and enhanced in HPS group;the reducing power of iron was weakened in all groups（except APB30 group）;there was no significant difference in Fe²⁺binding ability in APB group and Fe²⁺binding ability was enhanced in HPS group.3.The difference of polypeptides in body wall of sea cucumber after heat treatment was compared by polypeptomic technique.A total of 6092 peptides of FS,APB30,APB90,HPS30and HPS90 were identified in the body wall of sea cucumber,including 295 peptides in total and870,377,457,454 and 828 unique peptides,respectively.Among them,there were a total of1863 bioactive peptides.There was significant difference and negative correlation between FS group and sea cucumber body wall polypeptide in heat treatment group.Compared with FS group,APB30,APB90,HPS30 and HPS90 groups had 538,402,420 and 391 different peptides,respectively.The main biological processes involved in the FS,APB30,APB90,HPS30 and HPS90 differential proteins are intracellular protein transport,DNA repair,DNA replication initiation,homophilic cell adhesion via plasma membrane adhesion molecules,and microtubule-based movement,respectively.The differential proteins in FS,HPS30 and HPS90cell fractions are mainly distributed in the plasma membrane,while APB30 and APB90 are distributed in the nucleus and cytoplasm,respectively.Different sea cucumber body wall polypeptides mainly have molecular functions such as ATP binding and ATP hydrolyzing activity.4.The chemical composition and antioxidant activity of polysaccharides in body wall of sea cucumber were affected by different heat treatment methods.The HPS30（P）group had the highest relative content of total sugars（41.63%）,while the HPS90（P）group had the highest relative content of glyoxylate and sulphate groups with 10.93%and 26.48%,respectively.The monosaccharide composition of different sea cucumber body wall polysaccharides had the highest content of rockulose（66.57%～77.41%）.After heat treatment,the relative content of rockulose decreased in the APB（P）and HPS90（P）groups and increased significantly in the HPS30（P）group.The average weight molecular weights of FS（P）,APB30（P）,APB90（P）,HPS30（P）and HPS90（P）were 4.418×10⁵,3.256×10⁵,2.547×10⁵,4.266×10⁴ and 1.777×10⁴g/mol,respectively.After heat treatment,the molecular weight of polysaccharides in the body wall of sea cucumber decreased.The results of infrared spectrum analysis showed that the body wall polysaccharides of all groups of sea cucumber were polysaccharides containing fucose methyl,acetyl amino and sulfate.The exothermic peak temperature of polysaccharides in the body wall of sea cucumber in heat treatment group was lower than that in FS（P）group,indicating that heat treatment could reduce its thermal stability.The microstructure of polysaccharides in body wall of sea cucumber was significantly affected by different heat treatment methods.After heat treatment,cracks appear on the surface of APB30（P）group,pores of APB90（P）group increase,and the structure of HPS（P）group becomes tighter.The body wall polysaccharides of different sea cucumbers all had certain scavenging ability of DPPH,ABTS and hydroxyl radical,as well as iron reducing power and Fe²⁺binding ability,and all of them gradually increased with the increase of concentration.After heat treatment,the DPPH,ABTS and hydroxyl radical scavenging abilities of polysaccharides from body wall of sea cucumber were decreased,except for the enhanced Fe²⁺binding ability.5.The chemical composition and antioxidant activity of CPC supernatant during polysaccharide extraction from sea cucumber body wall were affected by different heat treatment methods.The supernatant of CPC was mainly protein,with relative content ranging from 39.67%to 50.68%.The total amino acid content of CPC supernatant in different sea cucumber body walls ranged from 31.39 to 47.38 g/100g.After heat treatment,the contents of essential amino acids and umami amino acids increased.The monosaccharide composition of CPC supernatant on the body wall of all sea cucumbers had the highest glucose content（40.68%～56.17%）.The CPC supernants of different sea cucumber body walls had certain scavenging ability of DPPH,ABTS and hydroxyl radical and Fe²⁺binding ability,and all of them gradually increased with the increase of concentration.After heat treatment,the DPPH radical scavenging ability of CPC supernatant on the body wall of sea cucumber was decreased;the free radical scavenging ability of ABTS was decreased except for APB30（C）group;hydroxyl radical scavenging ability was decreased in all groups except HPS30（C）group;there was no significant difference in Fe²⁺binding ability of APB（C）group,but the Fe²⁺binding ability of HPS（C）group was slightly decreased.