Study on the preparation technology of cold-pressed evening primrose oil by response surface methodology

Based on evening primrose seeds, cold-pressed method was used to obtain evening primrose oil.Pressing chamber temperature, pressing chamber pressure and moisture content were considered as factors, and content of γ-linolenic acid in evening primrose oil was employed as evaluation index. The combination design of quadratic orthogonal rotation was used to study preparation process of evening primrose oil. The regression equation was optimized by Matlab software for getting the optimal condition of the cold pressing conditions. The optimal conditions:moisture content was 7.2%, pressing chamber temperature was 78℃, pressing chamber pressure was 3.0MPa. The content of γ-linolenic acid in evening primrose oil was 9.26%with the optimal conditions, and the quality of evening primrose oil was up to exporting standards of Europe.