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 dopamine (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 (ΔI_{780 nm}) was linear to the PPO activity in the range of 0.10–6.0 U·mL^?1, with a regression equation of ΔI_{780 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.