Study On The Separation Of Linoleic Acid In Carya Cathayensis Sarg. And Synthesis Technology Of Conjugated Linoleic Acids

Conjugated linoleic acids (CLA) are unique unsaturated fatty acids with variousimportant biological and physiological functions. Their functionality and applications infoods, pharmaceuticals, cosmetics, and other industries have become hot researchtopics.However, the amounts of naturally occurring CLA are too little to satisfy thedemands of people. At the present, chemical synthesis methods are an effective way toobtain large quantity of CLA, and alkali isomerization technique to prepare CLA is simplerand practical. This method synthesizes CLA using linoleic acid or plant oil with highcontent of linoleic acid as starting material by the isomerization. Carya cathayensis Sarg.oil contains abundant unsaturated fatty acid, especially oleic acid and linoleic acid, so itcan provide raw material for the preparation of CLA. This study was carried out toresearch the extraction of linoleic acid from Carya cathayensis Sarg. oil, the separation andpurification technology, oxidation stability and antioxidant activity of CLA to develop anew way for intensive processing of Carya cathayensis Sarg. The results were as follows:(1) Both single factor and orthogonal experiments were used to optimize conditionsfor the separation and purification of linoleic acid from Carya cathayensis Sarg. oil byurea adduction fractionation. Effects of adduction temperature, time, the ratio of fatty acidto urea (W/W), and methanol to urea (V/W) on the purity and yield of linoleic acid wereinvestigated. The results showed under the optimal purification conditions with the ratio offatty acid and urea at0.4, the rate of methanol and urea at4, adduction temperature at-5℃,and adduction time of24h, the content and yield of linoleic acid in Carya cathayensis Sarg.oil were60.27%and40.16%, respectively.(2) Effects of related factors on the alkali isomerization of linoleic acid wereinvestigated. Factors of reaction time, temperature, and the weight ratio of the linoleic acidmaterial to KOH were selected to investigate the effects on the concentration of CLAbased on the single factor experiment. The isomerization process of linoleic acid wasoptimized by response surface methodology, and the regression model was establishedwith the concentration of CLA as the response value. The optimum process parameterswere obtained as: reaction time4h, reaction temperature174℃, the weight ratio of thelinoleic acid material to KOH1.87, propylene glycol to linoleic acid weight rate at2.Under the conditions the theoretical concentration of CLA was64.72%, and actualconcentration was62.87%, the error of2.86%.(3) The separation and purification of CLA by urea adduction fractionation were studied. Factors of the ratio between CLA and urea (W/W), between methanol and urea(V/W) and adduction temperature were selected to investigate the effects on the contentand yield of CLA. The experimental results were analysed by response surfacemethodology, and the corresponding mathematical regression models were establishedwith the content and yield of CLA as the test value.The content and yield of CLA wereresearched as the response values to optimize the purification process of CLA by analysissoftware of Design Expert7.1.3for the better content and yield of CLA after ureaadduction. The optimal purification conditions were the ratio of CLA to urea at0.44, theratio between methanol and urea at5.22, adduction temperature at1.5℃, adduction time of12h. Under above conditions, the theoretical purity and recovery of CLA were79.97%and39.14%, respectively. Values obtained from experiments were77.35%purity and40.79%recovery. Therefore, the relative differences between theoretical and experimental valueson purity and recovery were3.28%and4.22%, respectively.(4) Effects of antioxidants on the stability of CLA were studied.The acceleration ofCLA oxidation in the dark was achieved by regulating temperature (50℃). Relatedoxidative indexes (peroxide, anisidine and the total peroxide value) were detected toinvestigate the oxidation degree of CLA. The results showed that TBHQ was the best toimprove the stability of CLA, compared with VE, BHA, and0.2g/kg TBHQ was the mostsignificant to inhibit oxidation of CLA in the range of0-0.2g/kg.(5) The scavenging capacities of.OH, DPPH and superoxide anion(O2-.) weremeasured to determine the antioxidant activities of CLA in vitro. The results showed thatCLA could scavenge a certain amount of.OH, the clearance rate was58.78%with the2mg/mL of CLA, but the scavenging capacities of DPPH and O2-.was lower. Themechanisms of CLA to scavenge free radicals are still not clear and whether or not CLAcan act as an effective antioxidant is uncertain. So further studies are needed to clarify theantioxidant capability of CLA.