Optimization of Microwave and Conventional Extraction Methods to Extract Antioxidant from Onion Skin Extracts

The aim of this study was to prepare extracts from onion skin by using MAE and conventional (Soxhlet and maceration) and test their antioxidant activity and phytochemical analysis.

Manufacturers and researchers have recently become interested in using the trash out from fruit and vegetable businesses, due to its inexpensive and high amount of potent bioactive substances. The experiment was conducted in Department of Processing and Food Engineering, Vaugh Institute of Agricultural Engineering and Technology, SHUATS, Prayagraj, India.

Antioxidant activity (AOA) was assessed by Diphenyl Picryl Hydrazyl (DPPH) method and Half-maximal inhibitory concentration (IC50) value was recoded. Traditional techniques to extract antioxidant compounds from onion skin need a lot of energy and take a long time to react. Low yields and compound degradation are frequent effects of these circumstances. The maximum TPC and TFC were found as 519.25 mg/g gallic acid equivalent (GAE) and 120.975 mg/g Quercetin equivalent (QE) respectively, using 90% EtOH concentration with microwave at 300W. EtOH (90%) OS extracts showed the highest free radical scavenging activity with power f 400W of 86.980% with an IC50 value of 38.516 µg/ml. Among all methods, Yield of TPC, TFC and AOA of onion skin extract decreased using the following sequence: microwave assisted extraction >soxhlet extraction >maceration. As it can be seen, microwave gave the higher yield of phytochemicals and antioxidant activity.