Comparative study on the flavonoids extraction rate and antioxidant activity of onions treated by three different drying methods

Abstract

Onions, rich in flavonoids, with antioxidant, antibacterial, and other biological activities, are often used as extraction of raw materials to obtain health products with high flavonoids content. However, the amount of raw material consumption is large due to low yield of extracts from fresh onions. As a result, dried onions often are used as extraction materials. The effects of air drying (AD), freeze-drying (FD), and microwave freeze-drying (MFD) on the flavonoids extraction yield of onions were investigated. The most effective and economical method was hot AD. On the other hand, the flavonoids extraction rate of onions dried by MFD was the fastest. FD could also obtain high extraction rate, but it cost the highest energy consumption. In order to obtain relatively rapid, economic, and effective extraction of onion flavonoids, onions can be dried by MFD or AD method.

Keywords:

• Onion
• flavonoids
• extraction
• drying
• microwave freeze drying

Additional information

Funding

We acknowledge that this project was financially supported by the support of the National Key R&D Project, [No. 2017YFD0400900]. The authors also thank the National Natural Science Foundation of China under the contract of [No. 31671907]; the support of the Program for Science and Technology Innovation Team in Universities of Henan Province, [No. 16IRTSTHN009]; the support of Henan Natural Science Foundation, [No.182300410062].