Susceptibility of Stored Cocoa Bean Seeds to Ochratoxigenic Fungi in Ondo State, Nigeria

Abstract

Aims: To determine the susceptibility of stored cocoa beans to ochratoxigenic fungi in Ondo State, Nigeria. Place and Duration of Study: The study was carried out at Adekunle Ajasin University, Akungba-Akoko, Ondo State, Nigeria; and cocoa beans samples were collected from stalls in Ondo, Idanre, Oda-Akure, Oba-Akoko, Ile-Oluji, and Ikpenmen towns in Ondo State for a period of twelve months. Methodology: The serial dilution method was used in plating and isolating the fungi in cocoa bean samples while identification was done conventionally. TLC was used to determine ochratoxin A production by toxin producers. Results: Cocoa beans collected from stalls in Oba-Akoko had the highest mean fungal incidence of 195 x 105 cfu/g of cocoa bean while those from Idanre stalls had the lowest mean with 4.964 x 105 cfu/g of cocoa bean. Cocoa samples had high fungal incidence between July and September, 2014 compared to other months the study took. Penicillium, Fusarium, Verticicladium, Neocosmospora, Mucor, Rhizopus, Beaveria, Alternaria, Sachharomyces, Phoma were the genera isolated using Czapek Yeast Extract, and TLC screening showed that A. niger, A. ochraceous, A. carbonarius, A. terreus and A. niger are OTA producers. HPLC quantification showed that cocoa bean seeds collected from stalls in Idanre were the least contaminated by OTA while high concentration level of 32.09±22.9 ng/g was detected in Oba-Akoko area of Ondo State. Conclusion: The study showed that cocoa beans collected from different stalls in Ondo State were susceptible to ochratoxin A contamination, and generally high concentration of the toxin is produced in the wet season than in the dry season. The study further showed that ochratoxigenic moulds infesting stored farm produce such as cocoa bean seeds in Ondo State are majorly the Aspergillus species.