Enzymatic Preparation Of Glycerides Rich In Polyunsaturated Fatty Acids

ω-3 polyunsaturated fatty acids (ω-3PUFA), such as eicosapentaenoic acid(EPA) and docosahexaenoic acid(DHA), have good physiological activities. EPA and DHA are mainly consist in fish oils, but their contents are low in natural fish oils and need to be enhanced by certain technique. Traditional purification methods have many disadvantages, such as the solvent recovery difficulties, complicated operation and decomposition ofω-3PUFA, etc. Enzymatic preparation of glycerides rich in PUFA included deacidification, alcoholysis, molecular distillation and esterification, that provided the scientific basis of glycerides industrialization. The main contents were as follows:1.The method of enzymatic and alkaline combination was used in the ethyl esterification of fish oil with high acid value. First, lipase was used to catalyze the de-acid reaction of fish oil and ethanol, and the reaction conditions were optimized: molar ratio of triglyceride and anhydrous ethanol was 1:1, the amount of lipase Novozym 435 was 2%, reaction temperature was 45℃, oscillator speed was 180r/min, reaction time was 6h. Under the optimal conditions, the acid value of fish oil fell to 0.67 mgKOH/g from 10.20 mgKOH/g. And then sodium hydroxide was used as the alkaline catalyst for the further ethyl esterification, the yield of ethyl esters was 96.5% after 1.5h.2.Used the six steps molecular distillation to separate the fish oil ethyl esters and get PUFA ethyl esters. The content of DHA was enhanced from 27.57% to 75.81%. The total content of EPA and DHA was enhanced from 32.11% to 82.23%.3.PUFA ethyl esters and glycerol were used as the substrate in the enzymatic synthesis of PUFA glycerides. Tert-butyl alcohol was the solvent at atmospheric pressure, and the optimal reaction conditions were: molar ratio of glycerol and PUFA ethyl esters was 1:3, substrate concentration was 30%, the amount of lipase Novozym 435 was 2%, reaction temperature was 50℃, oscillator speed was 180r/min. Under the optimal conditions, the conversion of PUFA ethyl esters was 47.3% after 12h. Then, under vacuum condition, the conversion of PUFA ethyl esters reached 81.5% after 12h, and the contents of diacylglycerols, triglycerides and monoacylglycerols were 56.1%, 32.3% and 11.6%, respectively. The content of DHA and EPA was 74.6% and 5.5%, respectively.4. The effect for the oxidation stability of PUFA glycerides was TBHQ> VE> citric acid. In the orthogonal experiment, the optimal dosage of TBHQ, VE and citric acid was 200mg/kg, 500 mg/kg and 1000 mg/kg, respectively. The time when the peroxide value of PUFA glycerides reached 100meq/kg was 5.9 times as long as the one not adding antioxidants.