Simple and rapid detection of calcium peroxide in flour based on methanobactin peroxidase-like activity

Calcium peroxide is forbidden to be added to flour as brightener in many countries. A rapid and sensitive spectrophotometric method for the detection of calcium peroxide in flour was proposed. Methanobactin (Mb), a copper-binding small peptide of methanotrophs with excellent peroxidase-like activity, has been successfully applied for H₂O₂-mediated co-oxidation between phenol and 4-aminoantipyrine to give a colored product that can be detected at 505 nm. When the concentration of Mb-Cu was 6.5 × 10^-6 mol/L, the detection temperature was 50 ℃, and the detection time was 5 min, the linear range for quantification of calcium peroxide concentration was observed between 0.4 and 10.0 mg/L with R² = 0.99397. The limit of detection was 0.027 mg/L (3.34 mg/kg flour) and the average recovery of standard addition was 99.6%-100.5%. Mb was very stable and still maintained catalytic activity even at 50 ℃ in acidic medium, which gave the proposed method has simple process and rapid detection speed.