The absorbance at 420 nm (A420) was used as an indicator of colour developed in the final stage of Maillard reaction ( Fernandez-Artigas et al., 1999 and Morales, 2005). According to Fig. 2, a sharp increase of A420 in Maillard reaction system was observed with increasing temperature. The browning rate first increased rapidly, and then decreased slowly when the temperature rose up to 120 °C. The temperature-course of colour formation in this system showed the similar trend as found by Dattatreya and Rankin (2006). On the other hand, in thermal degradation system, the changes in A420 were negligible.