Aflatoxin In Market Peanuts And Pre-Treatments Prior To Roasting To Reduce Levels

Abstract

In the recent past aflatoxin in peanuts and the products has been a subject of controversy in Kenya. Brands of locally manufactured peanut butter were withdrawn from the market shelves on account of them containing levels of aflatoxin higher than the national tolerance for total aflatoxin of 10ppb. It has been established that Kenyan market peanuts contain high levels of aflatoxin. Roasting, the step expected to reduce aflatoxin levels during manufacture of peanut butter and products is reported not to be effective in lowering the toxin. This study was therefore designed to apply specific pre-treatments prior to roasting to reduce the aflatoxin levels to below the tolerance, to ensure similar levels in the roasted peanuts and products. The treatments included soaking in cold and warm water, warm solution of calcium hydroxide of concentrations 0.01 – 0.04%, and UV irradiation. One-kilogram samples of peanuts were collected from 20 vendors in Nyamakima, the main Cereal Market in Nairobi. By random sampling, 40 peanut vendors were selected from exhaustively. Using a semi-structured questionnaire, the vendors were interviewed for their socio-demographic, socio-economic and the peanut vending characteristics. The peanut samples were brought to the laboratory of the Kenya Bureau of Standards (KEBS) and analysed for moisture and aflatoxin. Then 100g of each sample were weighed in duplicates and each batch soaked in water, warm water and warm calcium hydroxide for periods of up to five minutes at one minute intervals, with light agitation. Each time the peanuts were drained of water then dried in an air oven at 80oC for 10 minutes to remove the surface water. A similar batch of peanuts in duplicates was spread on plastic paper as monolayer and irradiated with UV for up to 2 hours. Moisture was determined as percent by drying in a thermostatic air-oven at 105oC after grinding to pass through 4mm sieve to constant weight.