Abstract: An ultra-high pressure-assisted urea adduction method was adopted to enrich thepoly unsaturated fatty acids (PUFA) linoleic acid and linolenic acid from linseed oil, and the content and yield of PUFA in the filtrate were investigated with respect to operating parameters. The content of PUFA in linseed oil was 96.05% when treated under the following conditions: mass ratio of urea to fatty acid mixed 3:2, ratio of urea-fatty acid mixed to 95% (V/V) ethanol 5:14, and cooling of urea inclusion mixture at 20 ℃ for 30 min followed by exposure to 300 MPa for 20 min, which was similar to that (97.41%) achieved by the traditional freezing method (?18 ℃, 18 h). Moreover, the yield of PUFA in the filtrate was increased by 41.39% when compared with that obtained by the traditional method. Subsequently, we investigated the thermodynamic properties and crystal morphology of urea inclusion complexes (UIC) under different stress conditions using a differential scanning calorimeter (DSC) and a scanning electron microscope (SEM). The results exhibited that UIC were more prone to form a hexagonal crystal structure with regular morphology and that the crystals formed were distributed more densely with increasing pressure up to 300 MPa. Accordingly, ultra-high pressure-assisted urea adduction could improve the separation efficiency of PUFA, because the crystal structure of UIC was more regular and stable under pressurized conditions.

Key words: ultra-high pressure-assisted urea adduction, poly unsaturated fatty acids, separation efficiency, differential scanning calorimeter, scanning electron microscope