Rapeseed oil is the second most abundant produced edible oil in the world with low erucic acid and low glucosinolate. Thus, the quality of rapeseed oil had attracted global attention. Cold-pressed rapeseed oil appeared to be a preferred choice than refined oil as no solvent and less processing involved in the cold-pressing. The methods of cold-pressing and microwave pre-treatment on the extraction yield and bioactive compounds of rapeseed oil have been reviewed in this paper. Cold-pressed rapeseed oil offers health benefits due to its preserved fatty acid profile and bioactive compounds. High phenolic compounds, tocopherols, phytosterols, and carotenoids contents in the cold-pressed rapeseed oil offer health benefits like regulating blood lipid profile, insulin sensitivity, and glycemic control, as well as offer antioxidant and cytotoxic activity. Besides using as edible oil, cold-pressed rapeseed oil find applications in animal feed, chemical, and fuel.
The thermal pretreatment of oilseed prior to oil extraction could increase the oil yield and improve the oil quality. Phenolic compounds are important antioxidants in rapeseed oil. In this study, we investigated the impact of thermal pretreatment method on the rapeseed oil based on phenolic compound levels. Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis showed that the phenolic compound contents in the microwave-pretreated oil were higher than those in the oven- and infrared-treated oils. Sinapic acid (SA) and canolol (CA), which are the top two phenolic compounds in rapeseed oil, exerted well 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity with IC50 values of 8.45 and 8.80 μmol/L. The cell experiment uncovered that SA and CA have significant biological activities related to rapeseed oil quality, including increase of antioxidant enzymes superoxide dismutase (SOD), alleviation of reactive oxygen species (ROS), and cytotoxicity of HepG2 cells after the intake of excessive oleic acid. Further investigation indicated that SA and CA reduced cell apoptosis rate through Bax-Bcl-2-caspase-3 and p53-Bax-Bcl-2-caspase-3, respectively. Taken together, our findings suggest that microwave pretreatment is the best method to improve the content of phenolic compounds in rapeseed oil compared with oven and infrared pretreatments.