Understanding of the Role of Pretreatment Methods on Rapeseed Oil from the Perspective of Phenolic Compounds

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.

Combination of thermal pretreatment and alcohol-assisted aqueous processing for rapeseed oil extraction

BACKGROUND

The alcohol-assisted aqueous extraction processing (AAEP) of oil has many advantages such as no need for demulsification and relative low cost compared with enzymatic aqueous extraction processing (EAEP). Three kinds of thermal pretreatments including dry-heating, wet-heating and soak-heating followed by the AAEP of rapeseed oil were investigated.

RESULTS

Both soak-heating and wet-heating had a higher contribution rate to oil yield than dry-heating due to the enhancement of heat transfer rate owing to the high moisture content in the rapeseed cells. However, oil from soak-heated rapeseeds showed a much lower level on peroxide value (0.41 mmol kg^-1 ) than that of wet-heated rapeseeds (5.23 mmol kg^-1 ). In addition, transmission electron microscopy images illustrated that promoting effects of soak-heating and wet-heating on oil release were attributed to the coalescence of oil bodies. A relative low concentration of alcohol solution as an extraction medium, the highest oil recovery of 92.77% was achieved when ground rapeseeds (mean particle size: 21.23 µm) were treated with 45% (v/v) alcohol for 2 h at 70 °C and pH 9.0. Both the acid value and the peroxide value are lower than the commercial oil produced by extrusion and hexane extraction. Furthermore, the oil produced from AAEP also had higher content of tocopherols and lower content of trans-fatty acids than the commercial oil.

CONCLUSION

AAEP of oil from soak-heated rapeseeds is a promising alternative to conventional oil extraction methods. © 2019 Society of Chemical Industry.

Report-Physicochemical and Antimicrobial properties of canola (Brassica napus L.) seed oil

Canola oil has been used in the Pakistan for the treatment of various diseases and skin infections. Oil was extracted with n-hexane from the seeds of canola (Brassica napus L.) and was evaluated for free fatty acid value. Four microorganisms namely; Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas originals, and Klebsiella pneumonia, has known to cause some infections treatable with these oils were investigated. The results showed that all oil shown inhibitory effects against Klebsiella pneumoniae, Staphylococcus epidermidis, and Pseudomonas originals but no inhibitory effects was found against Staphylococcus aureus.