Study On Preparation Of High-purity Punicic Acid Ethyl Ester By Pomegranate Seed Oil

Pomegranate seed oil can protect the human immune system,and prevent atherosclerosis,cancer,obesity,diabetes as well as heart disease.Pomegranate seed oil has a wide range of applications in the field of medicine and health care.In recent years,people pay more and more attention to the chemical composition and pharmacological effects of pomegranate seed oil.Pomegranate seed oil is rich in polyunsaturated fatty acids,the most content of which is punicic acid,accounting for about 80%.Punicic acid is a kind of octadecatrienoic acid,and there are three conjugated double bonds.Punicic acid is one of conjugated linolenic acid.Punicic acid has several health benefits,including anti-cancer,lipid metabolism regulation,anti-inflammatory,anti-obesity and antioxidant activity.Because of the large conjugation system,punicic acid has poor stability.It's sensitive to oxidation and prone to polymerization.The punicic acid ethyl ester has the same function as punicic acid while the stability of punicic acid ethyl ester has better stability.What's more,punicic acid ethyl ester has no toxic side effects nor bad smell,making it easier to be absorbed.So ethyl esterification can increase the stability of punicic acid.In this research,pomegranate seed oil fatty acid was ethyl esterified and enriching punicic acid ethyl ester from pomegranate seed oil fatty acid ethyl ester by molecular disti Ilation.The ability to scavenge free radicals of punicic acid ethyl ester was also studied.Firstly,the physical and chemical properties of pomegranate seed oil were determined.It turned out that the appearance of pomegranate seed oil was light yellow,the color was Y20,R0.9,the acid value was 0.67 mg(KOH)/g,the saponification value was 187.60 mg/g,the peroxide value was 2.60 mmol/kg,the moisture content and volatile matter was 0.02%,and the average relative molecular weight was 900.The fatty acid compositions of pomegranate seed oil were also determined.The results showed that the content of palmitic acid was 3.11%,the content of stearic acid was 2.09%,the content of oleic acid was 5.21%,the content of linoleic acid was 7.80% and the content of punicic acid was 81.79%.Pomegranate seed oil has a high content of punicic acid which is beneficial to prepare high-purity punicic acid ethyl ester.Secondly,the ethyl esterification process of pomegranate seed oil fatty acid was studied,including the effects of the ethyl esterification temperature,the ethyl esterification reaction time,the molar ratio of alcohol and oil,as well as the amount of catalyst on the reaction.The best processing parameters were obtained by single factor test as follows: reaction temperature 75oC,reaction time 1.5 h,reactant molar ratio 7:1,and the content of catalyst 0.5%.Based on the results of single factor experiments,orthogonal experiments were designed to optimize the esterification conditions and the optimum processing parameters were obtained as follows: reaction temperature 75oC,reaction time 2 h,reactant molar ratio 8:1,the content of catalyst 0.5%.The ethyl ester convention rate was 95.88%.At the same time,the stability of fresh pomegranate seed oil and pomegranate seed oil fatty acid ethyl ester was compared.It was found that the stability of pomegranate seed oil fatty acid ethyl ester was better.Then enrichment of punicic acid ethyl ester from pomegranate seed oil fatty acid ethyl ester was realized by molecular disti Ilation.The influence of preheating temperature,feed rate,scrape speed and distillation temperature on enriching conjugate linolenic acid ethyl ester were analyzed by single factor experiment.The optimum operation conditions were obtained as follows: preheating temperature 70oC,feed rate 2 m L/min,scrape speed 120 r/min,distillation temperature I 120oC and distillation temperature II 160oC.Under these conditions,the content of punicic acid ethyl ester reached up to 95.23% from 80.68% after secondary distillation.The purified samples were determined by gas chromatography,infrared spectroscopy and nuclear magnetic resonance spectroscopy.Finally,the scavenging ability of punicic acid ethyl ester for DPPH free radical,ABTS free radical and OH free radical was studied.It indicated that punicic acid ethyl ester had a better ability to clear DPPH free radical,ABTS free radical and OH free radical.And the higher the content of punicic acid ethyl ester was,the better the removal effect would be.