Optimization of oil recovery from oilseed rape by cold pressing using statistical modeling

Cold pressing is frequently used to produce high-quality vegetable oils, especially from seeds with high oil content, such as rapeseeds. But, it encounters a challenge from the industrial demand for high oil yield. Modeling the cold pressing process using experimental and statistical approaches would help to understand the effects of cold pressing conditions on oil yield and process efficacy. Therefore, this work aimed to investigate the effects of nozzle diameter (8-12 mm), screw frequency (40-60 Hz), and press head temperature (40-80 degrees C) on the oil recovery from rapeseeds by cold pressing using response surface methodology coupled with a 3(3) full factorial design. An extended quadratic equation fitted the experimental data accurately and reproducibly, as proved by the acceptable coefficient-of-determination (R-2 = 0.873), a not significant lack-of-fit (p = 0.872), and a very low mean relative percentage deviation (+/- 6.7%, 35 data). The ANOVA revealed that nozzle diameter, press head temperature, their interaction, three-factor interaction, and squared nozzle diameter influenced pressed oil yield significantly. The optimal condition for obtaining the highest pressed oil yield (26.7%) within the experimental domain was a nozzle diameter of 10 mm, a screw frequency of 50 Hz, and a press head temperature of 80 degrees C. The crude oil extraction degree achieved by cold pressing was 60.8% compared to the Soxhlet method. The rapeseed oil contains predominantly oleic, linoleic, linolenic, and palmitic acids, agreeing with other reported rapeseed oils.