Uncommon occurrence ratios of aflatoxin B_(l9) B_2, G_(l9) and G_2 in maize and groundnuts from Malawi

摘要

We report an unusual anatoxin profile in maize and groundnuts from Malawi, with aflatoxin G_1 found routinely at equal or even higher levels than aflatoxin B_1. Aflatoxin B_1 (AFB_1) ratio in a contaminated sample is generally greater than 50 % of total aflatoxin (sum of aflatoxin B_1, B_2, G_1, and G2). In Malawi, the aflatoxin occurrence ratios were determined by examining LC-MS/MS and HPLC fluorescence detection (FLD) data of 156 naturally contaminated raw maize and 80 groundnut samples collectedin 2011 and 2012. Results showed that natural aflatoxin occurrence ratio differed. In 47 % of the samples, the concentration of AFG[ was higher than that of AFB,. The mean concentration percentages of AFB_1/AFB_2/AFG_1/AFG_2 in reference to total aflatoxins were found to be 47:5:43:5 %, respectively. The AFG, and AFBt 50/50 trend was observed in maize and groundnuts and was consistent for samples collected in both years. If the AFB[ measurement was used to check compliance of total aflatoxin regulatorylimit set at 10, 20, 100, and 200 Hg/kg with an assumption that AFB_1>50 % of the total aflatoxin content, 8, 13, 24, and 26 % false negative rates would have occurred respectively. It is therefore important for legislation to consider total aflatoxins rather than AFB1 alone.