Ultrasound-assisted extraction of antioxidant bioactive compounds from wastes of rapeseed industry and their application in delaying rapeseed oil oxidation

Rapeseed meal ethanol-wash solutes (EWS) are wastes generated from rapeseed meal as a pretreatment step to reduce the presence of antinutritional compounds. This study focused on employing and optimizing an ultrasound assisted extraction (UAE) of antioxidant bioactive compounds from EWS. The second aim was to fortify rapeseed oil with the best extract obtained, and to optimize this process. Both optimizations were carried out with the Response Surface Methodology (RSM), considering the combinations amplitude-time and concentration-time of homogenizing the sample with the oil as the assessed variables in the first and second process, respectively. The UAE achieved a higher content of total phenolic compounds (TPC) and antioxidant activity (AOA) than a conventional extraction. The parameters used for obtaining the optimum value of TPC (99.30 mg GAE/g) and AOA (148.99 mg TE/g) were the combinations of amplitude and time of 10% - 9.24 min and 15% - 0.76 min, respectively. The optimum extracts were mainly composed of phenylacetic acid and ferulic acid. The fortification of rapeseed oil with the optimum extracts delayed the oxidation up to 45% while the second optimization process allowed to increase this value to almost 61%. Therefore, EWS could be an alternative to synthetic antioxidants.