Degree Programme
Master of Science in Plant Pathology
Research Topic:
Effectiveness of Density Sorting in Reducing Aflatoxin B1 and Fumonisins in Maize Grains

Ngure Carolyne is a Kenyan born scientist with key specialization in plant pathology and biotechnology. Over the past 5 years, she has worked professionally both in the public and private sector. Currently, she is attached to Kenya Plant Health Inspectorate Services (KEPHIS) on a temporary basis.

Carolyne is set to earn her MSc. in Plant Pathology on the 11th of December 2020. Having come from a background of academicians, she has consistently worked towards achieving great academic heights despite all odds of balancing between work and family and financing part of the research work. 

She is a very hardworking and resilient person, with great determination to achieve the tasks set before her. 

Her goal is to achieve the highest academic level that one can achieve and offer solutions to the community especially in the area of plant disease diagnosis, prevention and management as well as enhancing food safety. 



Mycotoxins such as aflatoxins and fumonisins are prevalent contaminants of maize, which is a major staple food in Kenya. Aspergillus flavus, Aspergillus parasiticus and Fusarium verticilloides are the major producers of carcinogenic aflatoxins and fumonisins respectively. Currently there are no effective methods of decontaminating grains and whole consignments have to be destroyed. This study sought to determine the effectiveness of density sorting in reducing aflatoxin B1, fumonisins, Aspergillus spp. and Fusarium spp. populations in maize grains. 

Samples (n=206) were collected during the 2017 harvest crop from markets in eight counties in Western and Nyanza regions of Kenya. Sample numbers differed across counties ranging from 10-30 per county. All samples were analyzed for mycotoxins using an ELISA assay. Ten samples with more than 50 ppb of aflatoxin B1 and 4 ppm of fumonisins were weighed into 300 g with two replicates and sorted using a density sorter into heavy and light fractions constituting 65-75% and 25-35% of the original weight respectively. The effectiveness of density sorting in reducing mycotoxin-producing fungi was determined by isolation from 20 samples of the unsorted and 80 samples of the sorted heavy and light fractions.

Mycotoxin-producing fungi isolated from unsorted and sorted samples were Aspergillus spp., Fusarium spp. and Penicillium spp.  Prevalence of Aspergillus flavus was higher in 93% of the samples followed by Penicillium. at 85% and Fusarium verticilloides at 67%. Density sorting reduced fumonisins in 100% of the samples with an average of 71% reduction and aflatoxin B1 in 50% of the samples while the levels increased in the rest of the samples averaging the percentage change at -12.8%.

Density sorting can be used to reduce fumonisins and aflatoxin B1 effectively in maize grain but had no effect on mycotoxin-producing fungi. The density sorter machine should be improved for large scale use at a commercial level.

Research Supervisors

Research Supervisors

Prof. James   W. Muthomi

Prof. Rebecca J.  Nelson