Abstract: Objective: To obtain high quality, pure, natural hemp seed oil and meanwhile maintain the natural bio-activity of protein retained in hemp seed meal. Methods: One-factor-at-a-time design and response surface methodology were applied for the optimization of process parameters for the extraction of hemp seed oil by cold pressed method. A mathematical mode describing oil yield as a function of raw material water content, temperature, pressure and time was set up. The fatty acid composition and purity of hemp seed oil were analyzed by GC and peak area normalization method. Results: The optimal process parameters were determined through canonical analysis as follows: hemp seeds containing 4.5% water were pressed at 40 MPa and 59 ℃ for 36 min. Under these conditions, the yield of hemp seed oil was up to 82.74%. Hemp seed oil was found to be rich in linoleic acid, linolenic acid, oleic acid, arachidonic acid and other unsaturated fatty acids and have a total unsaturated fatty acids content as high as 89.80%. Conclusion: Response surface analysis is effective for optimizing the cold-pressed extraction of hemp seed oil. Hemp seed oil is rich in unsaturated fatty acids and can thus be seen as a functional oil with high nutritional value.

Key words: hemp seed oil, cold pressing, response surface methodology (RSM), gas chromatography (GC), fatty acid