| Antarctic krill oil is rich in omega-3polyunsaturated fatty acids, neutral lipids,phospholipids, astaxanthin and reaches great attention for the special structure in thatit contains a relatively high amount of omega-3fatty acids mainly esterified intophospholipids and is of unique biological effects. Generally, the pre-dry process isnecessary for current methods to extract kril oil and organic solvents are usually used.pre-dry is long, energy consumption and of high cost, active ingredients are easy tooxidation during the process, affecting the quality of krill oil. What more, organicsolvents extraction methods are complicated and of high cost, solvent residuesproblem is conspicuous. Due to the the problem of the drying process and the organicsolvents that restrict the large-scale utilization of Antarctic krill, it is of significantscientific value and social economy significance to applying green extractiontechnology for immediate extracting krill oil from wet krill matrix. SupercriticalCO2(SC-CO2) extraction technology, as a wide concerned and applied greentechnology at home and abroad, has been widely used in the separation, purificationand refining of active ingredients in natural products for its high selectivity,solvent-free residual and pollution-free.This study ditectly used wet Antarctic krill as raw material and extracted neutrallipids and phospholipids separately by two-step extraction. Firstly, SC-CO2extractiontechnology was applied to extract neutral lipids and astaxanthin directly andefficiently; then phospholipids were extracted from deoiled Antarctic krill by SC-CO2with cosolvent extraction method; afterwards,composition analysis and qualityevaluation of astaxanthin-concentrating neutral lipids and omega-3polyunsaturatedfatty acids phospholipids were carried on; finally, the preliminary study on theremoval of free fatty acids(FFA) and cholesterol from raw material of wet Antarctickrill by SC-CO2extraction method was carried on, to compare with abroad krill oil,the refined neutral lipids and phospholipids were blended in ratio and then the thequality of the blended krill oil was analyzed. Specific research contents, methods and results were as follows:Firstly, the feasible condition for efficient extracting of neutral lipids andastaxanthin from Antarctic krill with high moisture by SC-CO2was investigated.Results showed that the feasible condition for extracting neutral lipids and astaxanthinfrom high moisture content krill sample was at an extraction pressure of30MPa, anextraction temperature of55℃, a dynamic extraction time of3h, an ethanol tosample ratio of1:1(v/m).Under this condition, the extraction rate of neutral lipidsand astaxanthin was72.28%and81.32%, respectively. The extraction rate of neutrallipids and astaxanthin was lower than that of dry samples, but far higher than that ofsolely SC-CO2extraction from wet basis, indicating that the obtained condition wassuitable for the direct and efficient extraction of neutral lipids and astaxanthin.Post-extraction krill residues were with a moisture content of23.60%, indicatingmoisture in the krill sample was coextracted.Secondly, the optimal condition of SC-CO2with ethanol extraction to extractphospholipids from deoiled Antarctic krill residues was studied, the content andcomponents of phospholipids extracted were measured and compared with that ofethanol extraction. The optimum condition for extracting phospholipids were at anextraction pressure of30MPa, an extraction temperature of45℃and added8mLethanol per gram krill sample, the highest phospholipids yield was5.58%. SC-CO2with ethanol extraction method was with a lower phospholipids yield but a higherphospholipids content especially lecithin content comparing with ethanol extraction.Phospholipids components by the two methods were all characterized by PC and PE,but differ in content. SC-CO2with ethanol extraction method had an advantage overethanol extraction in preparing pure phospholipids.Then by analyzing the neutral lipids in the first stage and phospholipids in thesecond stage, the neutral lipids mainly contain triglyceride, phospholipids content waslow, cholesterol content was high, fatty acids compositions showed that total EPA andDHA content in neutral lipids was13.02%, FFA(Free Fatty Acids) content and POV(Peroxide Value) was high; While phospholipids extracts mainly containphospholipids, triglyceride content was low, cholesterol content was low, fatty acidscompositions showed that the total content of EPA and DHA was26.93%, inphospholipids FFA and POV was lower than that of neutral lipids.Finally, SC-CO2extraction technology was considered in the process ofremoving free fatty acid and cholesterol. Research showed that after processing for2 h under11MPa，40℃，about43.85%FFA and about46.03%was removed while thetriglyceride loss was lower than30%. The refined raw material was utilized tofurtherly extract neutral lipids and phospholipids, then blended them in a ratio of1:1in order to compare with Aker’s krill oil. By evaluating the quality of krill oil, resultsshowed that in the krill oil, phospholipids account for45.21%, astaxanthin was540μg/g, cholesterol content was1.86%, EPA content was10.20%, DHA was5.85%,FFA was14.12%, POV was3.60meq/kg. The krill oil obtained in this work wassame with that of Aker in components, while slightly differ in specific contents. TheSC-CO2extraction technique provided certain reference significance for developingaboard green deep processing techniques for freshly caught Antarctic krill.This wasalso meaningful for the the separation and purification of natural products from otherwet matrices. |
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