Aflatoxin and fumonisin contamination of maize and beans along the food and feed value chain in Babati district, Tanzania

Abstract

The natural occurrence of aflatoxins and fumonisins in maize and beans at harvest, during storage and along the value chain, including processed, feed and marketed products in three villages of Long, Sabilo and Seloto in Babati District, Manyara region, Tanzania, was investigated in the year 2013/14. The villages were chosen as they represents three different climatic zone. Total aflatoxins and fumonisins contamination in 440 at harvest maize samples had levels up to 26.2 μg/kg and 46.2 mg/kg, respectively. Aflatoxins contamination in 38 common beans samples had levels up to 3 μg/kg. The aflatoxin and fumonisin contamination in all beans samples were within the maximum tolerable limit (MTL) of 10 μg/kg and 2 mg/kg respectively, by East African Commission standards (EAC, 2011b). Parameter estimates from the generalised linear model (GENMOD) indicated that medium altitude low rain zone that lies between 1500 and 1850 metre above sea level (m.a.s.l) and representing Sabilo village (0.26) was the major factor pre-disposing maize to aflatoxin contamination, while early planting (-0.22), hand hoe tillage (−0.59) and ox tillage (-0.55) were the major factor reducing the aflatoxin contamination. High altitude high rainzone (Long village) that lies between 2150 and 2450 m.a.s.l was the most important factor reducing fumonisin contamination in maize with a parameter estimate of -2.93. Total aflatoxin and fumonisin levels were also determined in 574 maize and 106 bean samples stored by 60 farmers over a period of 180 days from august, 2013 to March, 2014. Maize samples from Seloto village were more contaminated (mean value of 3.24μg/kg) than those from Sabilo village (mean value of 3.12 μg/kg). Factors associated with higher aflatoxin contamination were storage for 0 to 80 days and storage with other crops, while for fumonisin most influential factor was storage of maize in granaries comparing to polypropylene and improved bags. The storage technique or facility that had a higher risk of aflatoxin development was polypropylene bags without any insecticides treatment (control) with a mean contamination value of 3.57 μg/kg and polypropylene bags with insecticides and pesticides treatment (normally used by most of farmers) with a mean value of 3.30 μg/kg. Lower aflatoxin levels were related to the use of traditional storage insecticides, sorting, and storage in improved bags. Among the maize and beans samples collected from the market (vendors) and from processors (small-scale mills) were whole maize grains, maize flour, feed (maize bran and bad-sorted maize not fit for human consumption but normally fed to animals) produced locally from the three villages. Maize bran had highest levels of aflatoxin with a mean value of 2.38 μg/kg and bad sorted portion with fumonisins mean value of 7.42 mg/kg, followed by whole maize with a mean aflatoxin value of 1.73 μg/kg and maize bran with a fumonisin mean value 1.02 mg/kg, while, dehulled maize was least contaminated with fumonisin. During milling mycotoxin become concentrated in bran that most commonly become animal feed. This would reduce the mycotoxins levels in the fraction that is normally used for food (maize flour and dehulled maize). All animal feed grade grain materials had levels lower than MTL of 20 μg/kg for total aflatoxin and a range of 5 to 100 mg/kg for total fumonisin (FAO, 2004; FDA, 2001). The observations made in this study call for use of best practices along the commodity value chain that can reduce contamination in order to improve food and feed safety.