Aflatoxin contamination of pods of Indian Cassia senna L. (Caesalpinaceae) before harvest, during drying and in storage: Reasons and possible methods of reduction

Abstract

The presence of aflatoxins in senna plants was studied in two different areas of India using an HPLC method. Only pods of Cassia senna angustifolia contained aflatoxins: leaves and flowers were free. Damage by insect larvae ( Ephestia elutella) led to aflatoxin formation by fungi in the pods. Fruits damaged by other factors can also contain aflatoxins. The occurrence of aflatoxins in senna pods in South India proved to be unevenly distributed. Before harvest, 55% of samples contained less than 2 μg/kg, and 25% more than 10 μg/kg, with a maximum of 255 μg/kg. Controlled sun drying of pods allowed the aflatoxin content to double, while drying in the shade was followed by a four-fold increase. Only a very small fraction of dried senna pods carried the maximum load of aflatoxins. During storage of Indian senna pods, the aflatoxin content usually fell. The smallest increase of aflatoxins, but still giving rise to unacceptably high levels, was achieved using a solar dryer. The formation of aflatoxins in Indian senna pods could also be reduced by application of NeemAzal T/S ® and even more by a fresh neem leaf water extract, but not to below the desired level of 2 μg/kg. Northern Indian harvest methods, used in South India, resulted in a reduction of aflatoxins, but again not sufficiently, and with a reduced economic output. Sudan senna ( C. senna acutifolia), grown in South India, showed resistance to fungal infections and the aflatoxin content was lower than in Indian senna ( C. senna angustifolia), in the field and in the laboratory, but growing Sudan senna elsewhere in India was not economical. The consequences of the findings are discussed.