| dc.description.abstract | Exposure of human populations to acute or sub-acute levels of aflatoxins in contaminated maize and
maize products is a major food safety concern in Kenya, particularly among the Kamba community.
In an attempt to address this concern, a study was conducted to investigate the effect of dehulling
and treatment of maize grains with chemical additives on the levels of aflatoxins in naturally
contaminated maize during the traditional muthokoi making and preparation process.
Seventy-two (72) samples of maize contaminated with aflatoxins to varying levels were taken from
naturally contaminated lots sampled from Makueni, Kitui and Machakos Districts during an
aflatoxicosis outbreak. In the first part of the study, 48 of these samples were each de-hulled
separately by pounding in a wooden mortar accompanied by intermittent wetting of the grain with
either distilled water, or 1 % (w/v) solution of iati (a local alkaline mineral salt traditionally used as
a cooking aid), or 1 % (v/v) sodium hypochlorite or 1 % (w/v) ammonium persulphate. For each
dehulling trial, the whole-grain maize sample, muthokoi and by-product, were analysed for aflatoxin
levels, total mould counts and Aspergillus flavus counts. Aflatoxin reduction was calculated from
the difference between aflatoxin levels in whole-grain maize and aflatoxin levels in muthokoi
expressed as a percentage of the aflatoxin levels in whole-grain maize.
In the second part of the study, samples of dehulled and whole-grain maize were treated with iati, by
soaking in graded solutions of the salt at room temperature for 6 and 12 hours. The effect of this salt
on the levels of aflatoxins was compared with that of sodium hypochlorite and ammonium
persulphate, chemical additives that have already been reported to degrade aflatoxins under similar
conditions. Other samples of dehulled and whole-grain maize were boiled in dilute solutions of iati.
The percentage aflatoxin reduction due to dehulling ranged from 5.5 % to 70.0 % with a mean of
46.6 %. Aflatoxin reduction during dehulling was dependent on the aflatoxin contamination level of
the raw-material whole-grain maize and the extent of dehulling achieved. Total mould and
Aspergillus flavus counts were significantly lower in muthokoi compared to whole-grain maize only
when chemically active dehulling aids were used. Recovery of moulds was dependent on the grain
wetting agent but none of the agents used exhibited ability to completely inhibit mould recovery on
muthokoi.
During treatment with chemical additives, aflatoxin reduction was higher in dehulled maize than in
whole-grain maize. The effects of ammonium persulphate and sodium hypochlorite were high,
reaching percentage reduction of 73.2 % and 72.2 % respectively, during overnight soaking of
dehulled maize in 1 % concentration solutions. Loss of aflatoxins following soaking treatments of
contaminated maize in solutions of iati was lower than that attained following treatment with
ammonium persulphate and sodium hypochlorite. Overnight soaking of muthokoi in 0.5 % (w/v)
solution of the salt resulted in mean aflatoxin reduction of 49.7 % without loss of original colour of
the maize. A further aflatoxin reduction of 86.1 % was attained after boiling muthokoi in 0.5 %
(w/v) solution of iati for 150 minutes.
The results of this study indicate that dehulling of maize grains to make muthokoi substantially
reduces the levels of aflatoxins in naturally contaminated maize. Overnight soaking of muthokoi in a
dilute solution of iati can be used to further reduce aflatoxin carry-over into the edible portion while
cooking in a dilute solution of the salt can significantly reduce toxicity associated with aflatoxin contaminated
maize. The process of muthokoi making, however, does not destroy or inhibit mould
recovery and hence the risk of aflatoxin build-up exists in case this product is stored under
conditions that favour growth of aflatoxigenic moulds.
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