Shortly, flour hydrolysate (obtained by overnight digestion with papain solution at 65 °C) was added to 3 mL reagent containing Fe3+ (1 g FeCl3 dissolved in 50 mL 3.5 M H2SO4), 15 M H2SO4 and
0.1 M glyoxilic acid. After incubation at 65 °C for 30 min, absorption was read at 560 nm.