Preconcentration of α-Vitamin E Using Urea Inclusion Method

Soybean deodorized sludge (SDS) contains rich tocopherols and large amounts of free fatty acids and is good resource to concentrate vitamin E, but free fatty acids and tocopherols have similar solubilities in supercritical CO₂, so it is very difficult to increase tocopherols concentration by supercritical CO₂ extraction. Urea inclusion can remove most of saturated fatty acids from SDS and provide better material for supercritical CO₂ extraction. The results showed that the molar ratios of SDS to urea and water content in solvent had remarkable effect on compositions in inclusion part and filtrate, refluxing time and temperature had little influence on urea inclusion compositions in the two parts, methanol and ethanol showed similar action when they were used as urea solvent. The best inclusion conditions are as follows: the molar ratios of SDS to urea were 1∶15,95% ethanol as solvent to dissolve urea, refluxing for 10 min at 60 ℃ and then the solution was kept at 1～2 ℃ for 6～8 h.Through urea inclusion, α-vitamin E could be increased from 0.57% in SDS to 1.62% in filtrate, while inclusion part contained large amounts of fatty acids with similar solubility in supercritical CO₂,and only 0.1%～0.2% α- vitamin E. Using filtrate as material to reconcentrate α-vitamin E by supercritical CO₂, the concentration of α-vitamin E can be increased to 5.6%.