Soy milk effect on antioxidant activity of tea and coffee

Abstract

Numerous studies have demonstrated the effect of cow's milk on the antioxidant properties of tea and coffee, which has been largely attributed to the interaction between milk proteins and plant polyphenols. In this work, we applied redox potentiometry using potassium hexacyanoferrates in assessing the antioxidant activity (AOA) of beverages prepared by adding soy milk to tea or coffee. The AOA of the drinks was calculated with adjustments for volume fraction and AOA of soy milk. Addition of 10–30% (v/v) soy milk to green tea, black tea, drip coffee and lungo had no effect on the AOA of the original drinks, and the recorded deviations were within ± 4%. Cappuccino made with 67% (v/v) foamed soy milk showed a 24% increase in AOA compared to espresso.