| Diacylglycerols(DAGs),recognized as safety(GRAS)food resources,are mainly used in foods and cosmetics and production of emulsifiers,stabilizers and carriers in the pharmaceutical industry.In this paper,Lipozyme TL IM was used to catalyze the transesterification of long-chain monoacylglycerols(MAG)rich in palmitic and stearic acid with medium-chain triacylglycerols(MCT)rich in n-caprylic and decanoic acids to prepare DAGs.The DAGs analysis method and preparation process conditions were selected,and the physicochemical properties of the reaction products were analyzed.The main results are as follows:(1)Analysis of product glyceride composition by gas chromatography and thin layer chromatographyThe analytical method was determined by reactions of glycerol with medium and long-chain fatty acids(esterification of glycerol with octanoic acid,decanoic acid,palmitic acid,and stearic acid,respectively,and esterification of glycerol with two of these fatty acids).First,the transesterification product was analyzed by thin layer chromatography,and the product was separated by thin layer chromatography.The gas phase analysis was performed,it was found that the separation effect was not significant.Then,qualitative analysis of the components was performed by using the DB-1ht and DB-17 ht capillary columns to determine the retention times of the corresponding single substance or the related substances.The gas phase analysis method with medium chain,medium and long chain,and long chain glyceride was finally determined and provided the basis for the test.(2)Preparation of DAGs by rotary evaporatorTo decrease the damage of enzyme caused by mechanical agitation,a rotary evaporator was applied as a reaction device.Single factor experiments were carried out to investigate the effects of reaction time,substrate molar ratio,reaction temperature,and enzyme addition amount on the content of DAGs in the product.The suitable preparation conditions for the rotary steaming method were as follows: molar ratio of raw materials(MAG: MCT)was 7:3,reaction time was 100 min,enzymedosage was 8%,wt,reaction temperature was 60°C.Under these conditions,the content of DAGs in the product was 36.42%.(3)Preparation of DAGs using packed bed reactor(PBR)The porosity of the Lipozyme TL IM enzyme was firstly calculated,and then the retention time of the starting material in the enzyme column was calculated by the porosity and the flow rate.In the PBR pilot test,the effects of reaction temperature,substrate molar ratio and raw material retention time on the content of DAGs in the product were investigated.The suitable conditions for the final preparation were reaction time of 6.5 min,reaction temperature of 60°C,substrate molar ratio(MAG:MCT)of 6:4,and content of DAGs was 26.58%.The suitable conditions for the PBR test were applied to the pilot reaction(reaction time was 15.0 min),in which the DAGs content in the product was 33.15%.(4)Analysis of the physicochemical properties of the reaction productsPhysicochemical properties of glyceride products obtained under suitable conditions of rotary evaporator and PBR were analyzed by polarized light microscopy(PLM),X-ray diffraction(X-rd),pulsed nuclear magnetic(p-NMR)and differential scanning calorimetry(DSC).According to the results,the properties of the product after transesterification were significantly improved compared to that before transesterification.For example,in a rotary evaporation reactor,the crystallization temperatures before and after transesterification were 56.19°C and 42.71°C respectively,which showed that the crystallization temperature has significantly decreased after transesterification.In the PBR reaction,the solid fat content after transesterification changed significantly as well compared with that before the reaction,and the crystal morphology was even and fine. |
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