Comparison of physicochemical and antioxidant properties changes during wine fermentation from three onion varieties

Onion is a vegetable member of the genus Allium and one of the major sources of flavonoids in diets. Wine fermentation is one of the oldest preservation methods, which has been applied mostly on fruits. The aims of this research were to study and compare the changes of physicochemical properties and antioxidant properties of different onion varieties (red, yellow, and white onions) during wine fermentation for 30 days. The result showed that fermentation rate of red onion was slower than other onions, expressed by alcohol content and pH of the wine produced. However, red onion had higher antioxidant capacities before and after fermentation than yellow and white onions from all three observed antioxidant capacities. After fermentation, there was increase in DPPH radical scavenging and Trolox equivalent antioxidant capacities in all onion varieties. In addition, anthocyanin content of red onion decreased in large amount, however, it didn't impact the total flavonoid content.