Previous research has claimed that antioxidants in coffee are produced by chemical reactions involving cholergenic acids in coffee beans.
But a recent study by Professor David Kitts and student Yazheng Liu from University of British Columbia, Canada, has found that antioxidants are formed by the so-called Maillard reaction, changing sugars and carbohydrates, proteins and other organic matter in food (coffee beans in this case) when exposed to high temperature.
There has been conflicting evidence presented in the past, with some researchers claiming increased antioxidant activity as coffee is roasted while others tout medium-roast as having more antioxidants present. This recent study sheds some light on the confusion, indicating that while antioxidants are created during green bean roasting, almost 90% of cholergenic acids, including caffeine, disappear.