Occurrence of aflatoxins in export-quality Pakistani rice Part B Surveillance

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.