Onion peel is a by-product of the onion. It contains higher levels of quercetin compared with the levels in onion and other vegetables and fruits. This study aimed to optimize ultrasound-assisted extraction (UAE) conditions for optimal antioxidant activities and phenolic compounds from onion peel using response surface methodology (RSM). The parameters of ethanol concentration (X1 : 40-60%), extraction time (X2 : 10-50 min), ultrasonic power (X3 : 150-250 W) were investigated. The extraction at X1 = 56.8%, X2 = 36.4 min and X3 = 200.8 W was considered as the optimal UAE condition since it provided the maximum DPPH (38.1 mg Trolox equivalent/g) and ABTS (77.8 mg Trolox equivalent/g) radical scavenging activities and total phenolic content (76.0 mg gallic acid equivalent/g). The experimental values agreed with those predicted by RSM models. In addition, the antioxidant activities and total phenolic content using UAE were significantly higher than those of conventional extraction. Results of this study indicated that UAE was the efficient method for total phenolic compound extraction from onion peel with good antioxidant activities.

Comparison of extraction methods for antioxidant compounds from onion peel : Ultrasound-assisted and conventional extractions

2019 Spring National Meeting

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