Occurrence of aflatoxins in export-quality Pakistani rice

A survey was conducted to assess the extent of aflatoxin B1, B2, G1 and G2 contamination of export-quality rice. Five hundred and nineteen batches of rice (including white, brown and sella rice) from various exporters were analysed for aflatoxins using Mycosep column clean-up and quantification with high-performance liquid chromatography, during the year 2010. Mean concentrations for aflatoxin B1 (AFB1) and aflatoxin B2 (AFB2) were 0.56 µg kg(-1) and 0.03 µg kg(-1) for brown rice, 0.49 µg kg(-1) and 0.03 µg kg(-1) for white rice and 0.73 µg kg(-1) and 0.02 µg kg(-1) for sella rice, with an overall positive (≥ the limit of detection of 0.1 µg kg(-1) for AFB1 and AFG1; and 0.05 µg kg(-1) for AFB2 and AFG2) incidence of 49%. Out of all analysed samples, only 1.9% was found positive for aflatoxin G1. Highly contaminated samples were found in the month of August, with findings for aflatoxin B1 (AFB1) and aflatoxin B2 (AFB2) of 16.65 µg kg(-1) and 2.64 µg kg(-1), respectively. During the whole year, monitoring aflatoxin concentrations exhibited a distinct variation according to the climatic conditions, with relatively high levels during March, July and August, which could be related to favourable environmental conditions.