Resonance Scattering Effect of Dopamine Product Particle and Its Application to Polyphenoloxidase Activity Assay

In pH 7.2 Na2HPO4-NaH2PO4 buffer solution, polyphenoloxidase （PPO） could catalyze the oxidization of do- pamine （DA） to form polymer particles in dark-red color, which exhibited a strong resonance scattering （RS） peak at 780 nm. In the chosen conditions, as the PPO activity increased, the RS intensity at 780 nm increased linearly. The increased RS intensity （△I780nm） was linear to the PPO activity in the range of 0.10--6.0 U·mL^- 1, with a regression equation of △I780 nm = 96.6C＋ 15.1, a relative coefficient of 0.9987 and a detection limit of 0.06 U·mL^-1 PPO. The proposed method was applied to detecting PPO activity in potato sample with satisfactory results.