Palm kernel agar: An alternative culture medium for rapid detection of aflatoxins in agricultural commodities

Abstract

The feasibility of using palm kernel agar (PKA) as an alternative culture medium to desiccated coconut
agar (DCA), the conventional medium for the recovery of aflatoxigenic fungi from mixed cultures and
the detection of aflatoxigenic fungi and direct visual determination of aflatoxins in agricultural
commodities was assessed. The medium recovered aflatoxigenic fungi in 48 h from mixed cultures and
agricultural commodities in 58 h as compared to 62 h obtained for the two treatments on desiccated
coconut medium. Aflatoxigenic fungi were detected in all the agricultural commodities except for
onions with maize having the highest value of 13.18% (w/w) followed by melon (10.97), yam flour (10.23)
and groundnut (8.52) as against 11.48, 10.0, 6.92 and 8.52% (w/w) obtained for DCA. All aflatoxigenic
strains produced a characteristic yellow pigmentation on a pink background and blue or blue green
fluorescence of palm kernel agar Under long wave UV light (366nm) as against the white background of
DCA, which often interferes with fluorescence with corresponding yield of aflatoxins. This shows that
the medium is able to efficiently detect aflatoxin production through direct visual observation of
fluorescence. Palm kernel agar (PKA) can therefore be routinely used as an alternative culture medium
for screening aflatoxigenic fungi and direct visual determination of aflatoxins in agricultural
commodities since it is faster and has a unique pink background for easy identification.