Optimization and kinetic modeling of oil extraction from white mustard (Sinapis alba L.) seeds

White mustard seed oil (WMSO) was extracted from the ground seed by cold pressing and Soxhlet extraction using n-hexane. A two-step process consisting of cold pressing of white mustard seed (WMS) and extraction of WMSO from press cake (maceration) was also employed to improve the overall WMSO recovery. The main fatty acids of the WMSO were unsaturated oleic, eicosenoic, erucic, linoleic and linolenic acid. The maceration of press cake was modeled on the basis of a 3(3) full factorial design with replication coupled with the response surface methodology. The analysis of variance and the quadratic equation were used for assessing the significance of the influence of solvent-to-cake ratio, extraction temperature and extraction time on WMSO yield and for optimizing the maceration process. All three individual process factors, the interactions of extraction temperature with solvent-to-seed cake ratio and time as well as the quadratic terms of solvent-to-seed cake ratio and extraction time had a statistically significant influence on WMSO yield at the 95% confidence level. The mean relative percentage deviation of +/- 2.3% and the coefficient of determination of 0.923 proved the adequacy of the developed quadratic model for WMSO yield. The predicted and actual WMSO yields under the optimal maceration conditions (70 degrees C, 6.5:1 mL of solvent per g of seed cake and 5 min) were 7.29 and 7.20 +/- 0.13 g/100 g, respectively. With the two-step process, the WMSO yield of 20.48 g/100 g was achieved, which was 99.2% of the WMSO yield obtained by Soxhlet extraction. This indicated that the two-step process could replace the energy- and solvent-intensive Soxhlet extraction of ground WMS. The model of instantaneous washing followed by diffusion described most adequately the kinetics of WMSO extraction from press cake in the applied experimental region. WMSO extraction from WMS press cake was shown to be as spontaneous, irreversible and endothermic.