Preparation And Evaluation Of Antarctic Krill Lipid

Antarctic krill lipids are rich in omega-3 polyunsaturated fatty acids(?-3 PUFA,mainly,EPA and DHA,phospholipids?PL?,as well as natural antioxidants,such as astaxanthin,and they have important physiological functions.However,high moisture content and high thermal sensitivity of Antarctic krill limited its use.In this study,a novel method of preparation of Antarctic krill lipids based on combining dehydration and subcritical lipid extraction technique were investigated and the physicochemical properties and unique structures of the lipid were evaluated.Besides,Antarctic krill lipids were assessed by animal experiments.Firstly,dehydration of Antarctic krill by combining heat pump drying with freeze drying was studied.Composition of the krill and the migration patterns of different type's moisture in the krill were analyzed.A novel technology of preparation of Antarctic krill based on combining dehydration was developed.Relevant parameters analyzed,such as water activity,glass transition temperature,drying time and energy consumption,color and structure of the dried materials,as well as the lipids,the transfer point was determined to be 40%.Antarctic krill dried by using different dehydration methods were compared.Results showed that samples dried by freeze drying and samples coupling dehydration had better lipid extraction yield,and the lipids had lower lipid AV and higher astaxanthin content.Methods of coupling dehydration can save 63%dehydration time and 50%dehydration energy compared with the freeze drying method.Furthermore,methods based on comprehensive quality evaluation method of the Antarctic krill powder were established,and it was found that the dried Antarctic krill?used for lipid extraction?prepared by coupling dehydration had advantages.Secondly,the lipid extracted by subcritical butane were studied.Effect of different extraction conditions were confirmed by single factor experiment methods.Then,the optimum conditions of the subcritical butane extraction were determined based on the response surface methodology?RSM?.Referring to the actual operation procedure,the optimum conditions were fixed as follows:temperature of 40°C,pressure1.0 MPa,dynamic extraction time 120 min,and the lipid extraction yield was 81.2±0.4%.In addition,the lipid extracted by using subcritical butane,traditional chemical solvents,and supercritical CO₂were compared.Results showed that the subcritical butane extraction method has a higher lipid extraction yield,and the lipids were less oxidized,rich in astaxanthin?248.4±5.2 mg/kg?,PL?28.7±1.4%?,and have the highest VE?67.7±3.2 mg/kg?.Thirdly,physicochemical properties and the structure of the lipids were analysed.The lipid prepared by the innovative technology have a high antioxidant capacity include 15.88 h of oxidation induction time and strong oxidation free quenching ability.Structures of the lipid including the fatty acids profiles of TAG,Sn-2 of TAG,molecular species of TAG and PL,astaxanthin and the form of astaxanthin esterwere determined and analyzeded.Results demonstrate that the principal fatty acids are C14:0,C16:0,C18:1,C20:1,EPA and DHA,however,the content of EPA and DHA was different.The content of EPA and DHA in TAG was close to 30%,which are lower than that found in the total lipid.The basic appearance of the Sn-2 fatty acid in TAG is in agreement with that of TAG,but the sum of EPA and DHA content was 44.64%,which is higher than that found in the total lipid.In addition,there are plenty of molecular species of EPA and DHA in TAG.PL mainly of PC were detected in the lipid,and the fatty acid feature of different types of PLis in agreement withh that of the lipid.Furthermore,Sn-1 or sn-2 of different kinds of PL is easily be occupied by EPA and DHA.The mainly form of astaxanthin is astaxanthin di-ester which is characterised by abundant of EPA and DHA.In addition,a comprehensive evaluation method for the quality of Antarctica krill was created based on aggregate indicators including the combination of sensory evaluation,basic index,chemical composition,unique structure and hazard factor.Finally,physiological properties of krill lipids were evaluated by using C57bl/6J mice with the high fat diet of palm oil and polar substances from frying palm oil.Effect of the krill lipid on the growth and development,liver function oxidative stress and glucose metabolism in mice were studied,and the role of total lipid in Antarctic krill was discussed at the gene level.Results indicated that a high fat diet is the most likely to lead to obesity under almost equal energy intake.Palm oil was more easily lead to obesity;polar substances were mostly the cause of the liver hypertrophy.Meanwhile,palm oil and polar material lead to the metabolic disorders of lipid and sugar in the mice,which caused mice's tissue damage,therefore,increased the possibility of cardiovascular disease and diabetes in the mice.Antarctic krill lipids intake mixed with high fat diet,showed a positive effect on animal health,including regulating the related expression,down regulated the srebp-1c gene and up regulated the PPAR?,which the former was associated with lipid synthesis and the later was related to lipid lipolysis.These results indicated that Antarctic krill lipids prepared by the new technology could reduce the risks of cardiovascular and other related diseases in the obese mice.