title: Influence of Sulfur Fertilization on the Antioxidant Activities of Onion Juices Prepared by Thermal Treatment.
abstract: Two onions (Sulfur-1 and Sulfur-4) cultivated with different sulfur applications were thermally processed to elucidate the effects of heat treatment on browning index and antioxidant activity. Sulfur-4 onion had higher sulfur content compared with the Sulfur-1 onion. After thermal processing, browning intensity was different between the two onions juices, with lower values observed for Sulfur-4 onion juice. This suggests that sulfur inhibits the Maillard browning reaction. The total reducing capacity of the juices increased at higher thermal processing temperatures; however, it was also lower in the Sulfur-4 onion juice. This suggests that the heat treatment of onions enhanced their antioxidant activity, but the effect was offset in the Sulfur-4 onion juice presumably due to higher sulfur content. This study indicates that sulfur, a core element for the functionality of onions, can decrease the antioxidant activity of thermally processed onions because of its potential as a Maillard reaction inhibitor.
authors.affiliation: Department of Food and Nutrition, Seoul Women's University, Seoul 01797, Korea.
authors.forename: Eunmi
authors.initials: E
authors.lastname: Koh
authors.affiliation: Department of Food and Nutrition, Kangwon National University, Gangwon 25949, Korea.
authors.forename: Jeonghee
authors.initials: J
authors.lastname: Surh
keywords: antioxidant activity; browning; onion; sulfur; thermal processing