Effect Of Production Practices, Storage Materials And Moisture Content On Fungal And Aflatoxin Contamination Of Maize And Maize Products
Maize is the staple diet of majority of Kenyan population with a consumption of 400g person" day". Several outbreaks of mycotoxicosis have been reported in Kenya almost on an annual basis in Eastern province since 1978. These outbreaks have caused a lot of concern because they have worsened the food situation, since maize is the main staple in almost every household. This study was therefore conducted to determine maize production practices, fungal and mycotoxins contamination of maize in Eastern and North Rift regions of Kenya and the effect of moisture content and storage materials on fungal growth and mycotoxins production. A survey was conducted in Makueni, Machakos, Kitui, Uasin Gishu and Trans Nzoia . districts during March-May 2008 cropping season. The survey only covered Eastern province during the October-December cropping season. Information gathered included agronomic practices, harvesting, drying, storage materials and structures used, transportation, processing and weather conditions during harvesting and storage. Samples of whole maize grain, semi-processed grain, flour, soils and posho mill sweepings were collected and fungal isolation was done on Czapek Dox agar medium. The fungi were identified based on cultural and morphological characteristics. The effect of storage materials and moisture content was determined by inoculating maize adjusted to different moisture levels with Aspergillus jlavus and stored using sisal, synthetic or polythene bags. Re-isolation of Aspergillus jlavus was done on Czapek Dox agar and Aflatoxin B1 .. was determined by Enzyme Linked Immunosorbent assay (ELISA). The study found differences in production and handling practices between Eastern and North Rift regions. Some of the practices could predispose maize to contamination with mycotoxin producing fungi. Such practices included planting of uncertified seeds, harvesting maize before safe moisture content, drying grain on bare ground and storage in living houses and in synthetic or polythene bags. Most farmers had good awareness on mycotoxins. Whole maize grain, maize products and soils were contaminated with mycotoxin producing fungi such as Fusarium, Aspergillus and Penicillium. Fusarium was the most commonly isolated pathogen. The Aspergillus species isolated included A. flavus, A. niger, A. ochraceus, A. clavatus, A. fumigatus, A. terre us and A. versicolor. Among the Aspergillus species, A. flavus had the highest frequency of isolation in both Eastern and North Rift regions. Maize sampled from Eastern region had a higher . frequency of isolation for A. jlavus than in the maize samples from North Rift region. Frequency of isolation for A. jlavus was higher in semi-processed than in maize samples and flour had the lowest frequency of isolation. Fusarium subglutinans was the most predominant species in Eastern region while F. proliferatum was dominant in North Rift. Aflatoxin B, was detected in maize and maize products at levels above the national legal limit of l Oug/kg. The maize products and regions differed in the amount of aflatoxin B1. Samples from Eastern regions had higher aflatoxin levels of upto 136.4 ug/kg. Contamination of grain was upto 77.4 ug/kg while semi-processed maize had higher levels of upto 136.4 ug/kg. Maize flour had levels of upto 40.9 ug/kg . Moisture level and storage materials significantly affected the growth of Aspergillus jlavus in inoculated maize during storage. Maize stored in sisal and synthetic bags had lower kernel infection with A. jlavus than polythene bags. There were no significant differences in kernel infection between sisal and synthetic bags. The number of disco loured and mouldy grain and kernel infection were significantly affected by moisture level and storage materials. Moisture levels above 13% encouraged higher infection with A. jlavus. The highest kernel infection with A. jlavus was promoted by 18% moisture content. The result of the study showed that some of the maize production and handling practices in Eastern Province predisposes the maize to fungal and mycotoxin contamination. In addition, the favourable conditions created by high temperatures and periodic drought, contributed to the higher fungal and aflatoxin contamination of samples from this region. The study also confirmed that unfavourable drying and storage practices like planting uncertified seeds, harvesting maize with high moisture content and storage in living houses was compounding the problem, Therefore, there is need for continued mycotoxin awareness campaigns to educate farmers, traders, transporters and processors.