MYCOBIOTA AND AFLATOXIN ASSOCIATED WITH STORED COCOA BEANS IN SOUTH WESTERN NIGERIA

Abstract

Cocoa bean is contaminated by mycotoxin-producing fungi due to poor agronomical practices during beans fermentation, drying and storage. This study aims to evaluate the associated mycotoxin-producing fungi in stored cocoa beans. Cocoa beans were collected from Oyo, Osun and Ondo states and that of CRIN (Cocoa Research Institute of Nigeria) serves as control and were bulked into 9 composite samples. The beans were cultured using pour plating technique on potato dextrose agar routinely prepared in the laboratory. The cultured isolates were subjected to morphological identification and aflatoxin was assayed from cocoa beans using thin layer chromatography technique. The moisture content ranged from 5.4 to the highest of 8.0. The pH indicated all were acidic, and it ranged from 0.0 to 6.1. Nine mycobiota species were distinctly identified from the cocoa beans: Aspergillus flavus, Syncephalastrum racemosu, Penicillium digitatum, P. roquefortii, Geotichum candida, Fusarium graminaerum, A. niger, A. carbonariusand Rhizopus stolonifer. High microbial load was recorded in beans of Abiri (0.312cfu/ml and 62.0×10^-5cfu/ml), Aba nla (304 × 10^-3cfu/ml and 106 × 10^-5cfu/ml), Elebesere camp (200 × 10^-3 cfu/ml and 92 × 10^-3cfu/ml), Calendar camp (176 × 10^-3cfu/ml and 9.0 × 10^-5cfu/ml), Amonloje (108 × 10^-3cfu/ml and 50 × 10^-5cfu/ml). All the cocoa beans sample from the selected study location do not show the presence of aflatoxin as classified by both Rf (Retention Factors) value and colour under long wavelength UV light. Aflatoxin was not detected though aflatoxingenic fungi that were isolated in the study, suggesting that aflatoxin production may not be as a result of storage.