Influence of microwave pretreatment on the flavor attributes and oxidative stability of cold-pressed rapeseed oil

This study investigated the effect of microwave (MW) pretreatment on oil yield and the microstructure of rapeseeds, and examined the variations in oxidative stability, tocopherol content and flavor attributes of rapeseed oils extracted by cold pressing or solvent-based methods. Rapeseed moisture content was adjusted to 15% and the seeds were subjected to MW treatment at 200, 400, and 600 W. Compared to untreated samples with the same moisture content, MW pretreatment significantly (p < 0.05) increased the oil yield (by 9-23%), and total tocopherol contents (by 17-23%). Additionally, the oxidative stability of oils extracted from MW-pretreated rapeseeds was significantly (p < 0.05) improved. The analyses of headspace solid-phase microextraction gas chromatography mass spectrometry showed that the relative amount of of pungent compound 4-isothiocyanato-1-butene reduced by 74-95%, whereas that of the non-pungent compound methallyl cyanide increased by 95% in the oils extracted from MW-pretreated rapeseeds. Heterocyclic compounds such as furans and pyrazines appeared in the oils after MW pretreatment and created a special roasted flavor, suggesting that MW pretreatment had a positive effect on the flavor of rapeseed oils.