Occurrence of aflatoxins in parboiled rice in Sri Lanka

In Sri Lanka, rice is the main staple which is mostly processed into parboiled rice. The levels of aflatoxin B1 (AFB1) and aflatoxin G1 (AFG1) in parboiled and raw milled rice collected from major rice producing areas and rice consuming townships were estimated. In almost all the samples of parboiled rice examined, the AFB1 and AFG1 contents were significantly higher than in raw milled rice. The highest AFB1 content was 185 micrograms/kg and AFG1 content 963 micrograms/kg. These samples were collected from a major rice producing/milling district where the mean relative humidity is 78% and mean annual temperature 27 degrees C which is the highest amongst the rice growing areas in Sri Lanka. Raw rice was either free of aflatoxins or when toxins were detected, they occurred in less than 10% of the samples. The frequency of occurrence of surface fungal flora (Aspergillus/Penicillium) and aflatoxin content in market samples was closely related. Brownish or greenish moldly rice samples with fermented odour contained over 1000 micrograms/kg of AFB1.