Microwave and pulsed electric field assisted extractions of polyphenols from defatted canola seed cake

Summary The incorporation of microwave and pulsed electric field (PEF) technologies in optimising the extraction of polyphenols from defatted canola seed cake was determined by Box-Behnken response surface methodology, using three parameters of microwave treatment (power, time and liquid: solid (L:S) ratio) and four parameters of PEF (ethanol concentration, time, frequency and voltage). After microwave and PEF pretreatments, the polyphenols of defatted canola seed cake were extracted by ultrasound treatment under fixed variables (200 W of ultrasonic power, 70 °C of water bath and 20 min of extraction time). The measured responses were total phenolics, total flavonoids, the DPPH˙ scavenging activity and ferric reducing antioxidant power (FRAP). The maximum yields of all responses were achieved under optimum conditions of microwave processing (5 min, L:S ratio of 6.0 and 633.3 W) and PEF-assisted extraction (30 V, 30 Hz, 10% ethanol concentration and 10 s).