Abstract: Nitrogen gas was used to deodorize decolorized evening primrose oil instead of conventional steam distillation. The operating conditions including temperature, time and gas flow rate were optimized by response surface methodology based on peroxide value. The results showed that the optimum process conditions were determined as follows: temperature 144 ℃, time 3.5 h, and gas flow rate 2.1 mL/min. Under these conditions, the peroxidate value of deodorized evening primrose oil was 0.321 mmol/kg, which was effectively reduced compared with that before deodorization. In addition, the solvent residue was 0.02 mg/kg, and linolenic acid was effectively retained in the oil. The quality of the evening primrose oil could meet the industrial requirements. This study provides a new process and theoretical basis for improving the stability of evening primrose oil.

Key words: evening primrose oil, nitrogen deodorization, peroxide value, reduction, effect