Reduction of aflatoxins by extrusion-cooking of rice meal

The objective of this work was to determine the reduction of aflatoxin B-1 (AFB(1)), B-2 (AFB(2)), G(1) (AFG(1)), and G(2) (AFG(2)) as a function of initial moisture content of samples (24%, 27% and 30%), barrel temperature (140, 170, and 200 degrees C), and residence time (30 to 70 s) when artificially contaminated rice meal was extrusion-cooked. Extruded and unextruded samples were analyzed by high-performance liquid chromatography (HPLC). Extrusion-cooking was observed to reduce aflatoxin (AF) content, which ranged from 51% to 95% depending on the type of AF and the studied variables. Only in the case of AFG(2) was it found that the higher the temperature, the higher the moisture content, and the longer the residence time, the greater the reduction. Moisture content had a significant influence on reducing AFB(2), AFG(1), and AFG(2) whereas it was not a significant factor affecting the levels of AFB(1). Regardless of the type of AF, the lowest reductions were achieved at a temperature of 140 degrees C. Even though theoretically greater losses would be expected at highest temperature, AFB(1) and AFB(2) were more reduced by 170 degrees C than by 200 degrees C while AFG1 reductions were not statistically different when processing at 170 degrees C and 200 degrees C. The decrease of AF followed 1st-order kinetics; the fastest treatment in reducing AF was that at 200 degrees C when samples containing AFG(2) were wetted to 24% and when samples containing AFB(1), AFB(2) and AFG(1) were hydrated to 27%. By contrast, the slowest treatments were observed at a barrel temperature of 140 degrees C.