Bisulfite Degrades Aflatoxin: Effect of Temperature and Concentration of Bisulfite

Bisulfite reacted with aflatoxin B₁ and G₁ resulting in their loss of fluorescence. The reaction was first order with rate depending on bisulfite (or the bisulfite and sulfite) concentration(s). Aflatoxin G₁ reacted more rapidly with bisulfite than did aflatoxin B₁. In the presence of 0.035 M potassium acid phthalate-NaOH buffer (pH 5.5) plus 1.3% (vol/vol) methanol at 25 C, the reaction rate constant for degradation of aflatoxin G₁ was 2.23 × 10^-2h^- and that for aflatoxin B₁ was 1.87 × 10^-2h^- when 50 ml of reaction mixture contained 1.60 g of K₂SO₃. Besides bisulfite concentrations, temperature influenced reaction rates. The Q₁₀ for the bisulfite-aflatoxin reaction was approximately 2 while activation energies for degrading aflatoxin B₁ and aflatoxin G₁ were 13.1 and 12.6 kcal/mole, respectively. Data suggest that treating foods with 50 to 500 ppm SO₂ probably would not effectively degrade appreciable amounts of aflatoxin. Treating foods with 2000 ppm SO₂ or more and increasing the temperature might reduce aflatoxin to an acceptable level.