| Medium chain triglycerides is a kind of functional lipids,included caprylic triglyceride,capric triglyceride and caprylic-capric triglyceride.Due to its efficient digestion and absorption,it plays an important role in human nutrition,the pharmaceutical industry,cosmetics,and so on.This paper was carried out from enzymatic synthesis of caprylic triglyceride(TG)to deacidification purification.Experiment was composed of four parts:determination of detection method,the optimization of the enzymatic synthesis conditions,and the deacidification by liquid-liquid extraction and molecular distillation.A method of gas chromatography with programmed temperature was developed for analyzing the composition and content during the synthesis of the TG by enzyme.The results showed that the fatty acid(FFA),monoglycerides(MG),diacylglycerol(DG),triglycerides(TG)were well separated,and the position isomers of 1,3,1,2-DG were split obvious.Peak area and concentration of four substances showed a good linear relationship,and the linear correlation coefficient is 0.9972-0.9999?The RSD of concentration was 0.261-2.527%,and the recovery was between 95.65%and 102.54%,RSD was 0.728%-3.028%.This method can be used to detect the intermediate product MG and DQ and the final product TG.The medium-chain triglycerides were synthesized from caprylic acid and glycerol by Novozyme 435 in a solvent-free system,and the reaction conditions were optimized by response surface methodology.Using the fast speed of reaction before 6 hr of the whole reaction time,the reaction time,temperature,enzyme load and substrate molar ratios were determined as main four factors for this experiment to get the optimum conditions for each.Through single factor and response surface experiment,the optimum conditions could be obtained in a short time:reaction temperature 94 ?,reaction time 8 h,enyzyme load 4%(rasis on the mass of fatty acid),substrate molar ratio 3.5:1(fatty acid:glycerol).The triglycerides yield was 83.9%under these conditions,which was closed to the predictive value 86.66%got by response surface.After five times of experiments with the same enzyme,the enzyme still had high activity,and the triglycerides yield was about 76%.The method of ultrasonic-assisted liquid-liquid extraction is used to purify the TG using aqueous ethanol as a solvent to investigat the extraction temperature,ultrasonic power,ultrasonic time,the moisture content and the ratio of solvent:oil.The results showed that water content and the ratio of solvent:oil impacted the purification of TG,significantly.But temperature had less influence on purification,and ultrasonic almost had no effect.Through single factor experiment and response surface,liquid-liquid extraction conditions were optimized:the moisture content was 38%,the ratio of solvent:oil was 9:1.And under this condition,the fatty acid residue was 2.03%± 0.07,deacidification rate was 85.36%± 0.61,TG loss was 4.17%± 0.04,which was similar to the predictions got from regression model.With the optimized conditions,the secondary extraction was carried out.The moisture content was 38%,and the ration of solvent:oil ratio was 9:1 at the secondary extraction conditions.The fatty acid residues was 0.3%,and TG purity was 95.8%f inally in the TG with extracted twice.The secondary molecular distillation was used to refine the TG,the method could remove most of the FFA,and would prevent the color changing deeply.Comprehensive experiment design by two factors was used to optimize parameters of the first level molecular distillation.The optimum parameters for production of TG with low acidity and light color were as follows:evaporator temperature 110??feed flow rate 3d/s(close to 3.6g/min).On the basis of data analysis of the primary molecular distillation,the secondary molecular distillation process conditions could be as follows:evaporator temperature 110 ?,feed flow rate 3d/s(close to 3.6g/min).After twice molecular distillation,the FFA content was 0.34%,the DG content was 6.6%,and the TG was 93%,and the edible oil was 99.6%. |
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