The Study On Fractionation Of Palm Oil Using Melt Layer Crystallization

Palm oil,originated from the pulp of palm fruit,is a type of edible vegetable oil with the highest output and demand in the world.Therefore,as the commercial edible oil with the largest market demand,the application value of palm oil is very huge.The fractionation of palm oil can greatly increase its application value.However,the traditional crystallization fractionation process has manys problems,such as high energy and long time consumption,and difficult solid-liquid separation operation.In this paper,two by-products of palm oil,stearin and olein fractions,were successfully separated by using the green and efficient static layer melt layer crystallization,which strongly improved the application value of palm oil.According to the thermodynamic characteristics of palm oil and experimental design,the optimal parameters of the crystallization and sweating process of palm oil were determined,and palm stearin and olein with desirable properties were obtained.First of all,26 °C was determined as the critical point of crystallization temperature by DSC,and the melting point of palm olein product was obtained as 19.79 ± 0.14 °C.The solid fat content(SFC)was 16.51 ± 0.19% at 20 °C,and the iodine value(IV)was 61.2 ± 0.17.While the melting point of palm stearin product was 45.65 ± 0.37 °C,with SFC = 80.48 ± 0.49% at 20 °C,and IV= 35.8 ± 0.15.Based on the experimental data from crystallization process and the heat and mass transfer model of static layer melt crystallization,the heat and mass transfer of palm oil crystallization and sweating process were investigated.On the basis of previous studies,considering the change of solid-liquid interface temperature with the temperature of refrigerant,the model was calculated by analytic iteration method.Within the scope of the study,the simulation result is in a good agreement with our experiment.Finally,the properties of palm oil soft stearin end products were analyzed systematically.Through the combination of gas chromatography(GC)and liquid chromatography-mass spectrometry(LC-MS),saturated fatty acids and triglycerides with high melting point in the mother liquor of palm oil were transferred to the crystallization tube because of thermal driving force.Palmitic acid and oleic acid were the main fatty acid of the palm oil products.Differences of melting point of olein and stearin products were indicated by DSC analysis.It could be concluded that olein and stearin products can be further separated at the crystallization temperature above 18 °C and 40 °C,respectively.Avrami model was successfully applied in the analysis of crystallization kinetics.Results showed that the increase of crystallization temperature would lead to the palm stearin crystal changed from plate-growth to spherical growth,while for oleins,the nucleation would change from heterogeneous to instantaneous.