Pulsed ultrasonic-assisted extraction of proteins from double-low defatted rapeseed

The pulsed ultrasonic-assisted extraction of proteins from the double-low defatted rapeseed meal was studied.The rapeseed meal was prepared by traditional press oil technology.The optimum extraction condition obtained through single effect factor and orthogonal experiments was as following: pH=12,ultrasonic power 875 W,ratio of material vs water 1∶35(g/mL),extraction time 85 minite,dosage liquor temperature 48±3 ℃,on-time of the pulse 3 s and off-time 2 s.The extraction ratio of protein under above condition was 83.97%.The rapeseed proteins were precipitated at pH=4.5.The extraction yield of 52.18% and protein content of 68.18% were obtained.Compared with traditional alkaline method,under the similar conditions of the pH,ultrasonic power,ratio of water vs material and dosage liquor temperature by using the pulsed ultrasonic-assisted extraction,the extraction ratio and yield of protein were increased by 38.04% and 94.56%,respectively.The extraction time was decreased by 15%,and content of protein in extract was higher than that using traditional alkaline method.Content of sodium hyposulfite in extract was 0.06%,lower than the index in the National Standard of China(content of sodium hyposulfite is less than 1.85%).