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Separation Of Polyunsaturated Fatty Acids From Flaxseed Oil By Micromolecular Joint With Ultra-high Pressure&Urea Adduction Method

Posted on:2019-04-24Degree:MasterType:Thesis
Country:ChinaCandidate:K L ZhuFull Text:PDF
GTID:2371330545996975Subject:Agricultural Products Processing and Storage
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Linoleic acid and linolenic acid,the two polyunsaturated fatty acids(PUFA),are essential fatty acids of human body and have good effects on cardiovascular and cerebrovascular diseases,arthritis and so on.The content of linoleic acid and linolenic acid is more than 60% in flaxseed oil.Therefore,isolating and purifying of PUFA from flaxseed oil is an important way to get high-purity linoleic acid and linolenic acid.Urea adduction method is a common method for separating and enriching PUFA,but it has some disadvantages such as long duration,low product yield and poor separation selectivity of monounsaturated fatty acid(MUFA)and PUFA.In this research,in order to improve the efficiency and selectivity of PUFA,ultra-high pressure & urea adduction method and micromolecule assisted with low temperature & urea adduction method were adopted to enrich the PUFA in flaxseed oil.The main results were as follows:(1)The content of PUFA in ultra-high pressure & urea adduction method was similar to the traditional method(-20℃,20h),however,the yield of PUFA in it increased by 44.2%.The optimal conditions for the separation and purification of PUFA from flaxseed oil by ultra-high pressure & urea adduction method were as follows: urea: mix fatty acid(MFA): 95% ethanol was 3:2:14(w/w/v)and urea mixed solution was cooled for 30 min at 20℃.Then 300 MPa pressure was exerted and maintained 20 min.In this case,the content was 93.14% and yield was 74.48% of PUFA,respectively.The crystal of urea inclusion complexes was detected by XRD.It found that there was no significant difference(P>0.05)in interplane spacing of crystal between ultra-high pressure & urea adduction method and traditional urea adduction method(-20℃,20h),this showed that traditional low temperature & urea adduction method replaced by ultra-high pressure & urea adduction method did not change the crystal structure.Crystals in the inclusion phase under different pressures were detected by differential scanning calorimeter(DSC)and scanning electron microscope(SEM).The results showed that when the pressure was less than 300 MPa,increasing pressure could promote the crystallization of urea inclusion compound(UIC)to form hexagonal crystals,and the crystal morphology tends to be regular,the distribution of crystals was more concentrated.(2)Tartaric acid and citric acid assisted with low temperature & urea adduction method were used to enrich PUFA from flaxseed oil.Under the premise of ensuring the separation efficiency of flaxseed oil(linoleic acid and linolenic acid),the separation selectivity of PUFA in non-inclusion phase and inclusion phase increased from 2.74 to 3.21 and 3.80,respectively.Fumaric acid,malic acid,tartaric acid and citric acid assisted with traditional urea adduction method can increase the selectivity of MUFA and PUFA,but considering the content and yield of PUFA in non-inclusion phase,the separation efficiency and separation selectivity of PUFA were better when the ratio of tartaric acid/MFA(w/w)was 1: 2 and citric acid/MFA(w/w)was 1: 1.After an in-depth study on the separation effect of PUFA in flaxseed oil by tartaric acid and citric acid assisted with low temperature & urea adduction method.In summary,PUFA had better separation and selectivity under the citric acid/MFA(w/w)ratio of 1:1.In this case,the content of PUFA in non inclusion phase was 89.31%,th e yield was 70.75%,and the separation degree was 3.80.(3)The content of PUFA from flaxseed oil in citric acid assisted with urea adduction method combined with ultra-high pressure & urea adduction method was similar to traditional secondary freezing inclusion method.But the yields increased by 1.12 times,and the separation degree increased 34.38%,respectively.ultra-high pressure & urea adduction method combined with citric acid assisted with urea adduction method,and citric acid assisted with urea adduction method combined with ultra-high pressure & urea adduction method can make the the content of PUFA from flaxseed oil more than 99%,but compared to the traditional secondary freezing inclusion method,the yield increased 0.94 times and1.12 times,and the separation selectivity in non-inclusion/inclusion phase increased by 23.44% and 34.38%,respectively.Citric acid assisted with urea adduction method combined with ultra-high pressure & urea adduction method is a better process for enrichment of PUFA from flaxseed oil.The process is as follows: when the ratio of urea,MFA,95% ethanol,citric acid was 3:2:14:2(w/w/v/w),urease mixture was crystallized at 4 ℃ for 18 h,the fatty acids were obtained from processing sample in non-inclusion phase.The second inclusion was carried out with the ratio of urea,MFA,95% ethanol was 3: 2: 14(w/w/w),high pressure of 300 MPa for 20 min,the content of non-inclusion phase(linoleic acid + linolenic acid)was 99.34%,the yield was 68.32% and the separation selectivity was 3.44.
Keywords/Search Tags:ultra-high pressure & urea adduction method, polyunsaturated fatty acids, separation efficiency, separation selectivity
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