Distribution of Aflatoxin B1, B2, G1, and G2 in Various Fractions of Rice

Abstract. Aflatoxin, especially the Aflatoxin B₁, is a known carcinogen that poses health hazards to consumers of grain and grain co-products. At the present, United States Food and Drug Administration (FDA) regulates the level of aflatoxin B₁ at 20 ppb or less for grain destined for human consumption, and 300 ppb or less for feed. Beyond the set limit, the grain has to be disposed which represents a significant economic loss to the producers. Contaminated grain could be processed to reduce concentrations of aflatoxin to levels that meet other end-uses. The objective of this study was to investigate the potential to ameliorate aflatoxin-contaminated rough rice by milling treatments. Samples of long-grain, pureline rough rice (cv. Cheniere), naturally contaminated with aflatoxin, were used in this study. The initial concentration of aflatoxin B₁, B₂, G₁, and G₂ in the rough rice were determined as 27, 9.5, 2.5, and 0 ppb, respectively. The rough rice samples were dehulled and milled at three milling degrees (30, 45, and 60 s of millings). The concentrations of Aflatoxin B₁, B₂, G₁, and G₂ in various constituents of the rice such as hull, brown rice, and milled rice and bran obtained after different milling durations were determined using Ultra-Performance Liquid Chromatography (UPLC) coupled to Triple Quad Detector. Two Multiple Reaction Monitorings (MRMs) were utilized to provide a qualitative and quantitative assessment of each Aflatoxin. Based on the results, aflatoxin levels decreased as milling duration increased. For brown rice, aflatoxin B₁ and B₂ concentrations were at 29.5 ppb and 8.5 ppb, respectively. Milling rice samples for 60 s reduced the concentration of aflatoxin B₁ 5-fold and completely removed all the aflatoxin B₂. Aflatoxins were found mostly in the rice bran, and were highly concentrated especially in the outer bran layers as evidenced by concentrations of aflatoxin B₁ ^{(214 ppb; 121 ppb) and B₂ (16 ppb; 9ppb) after 30 and 60 s of milling, respectively. Aflatoxin G₁ was only detected in rough rice and brown rice, but not after 30, 45 and 60 s of milling. Aflatoxin G₂ was not detected in any of the rice constituents analyzed. These findings could benefit the rice industry by helping to find an effective strategy to utilize aflatoxin contaminated rice.}