Ochratoxin A Production by Cocoa Infested Aspergillus Species in Ondo State, Nigeria

Aim: To determine ochratoxin A production by cocoa bean seeds infested Aspergillus species in Ondo State, Nigeria.

Place and Duration of Study: Cocoa bean seeds were randomly collected from six local government areas namely Idanre, Akure, Owo, Akure, Oba-Akoko, and Ile-Oluji known to be highest cocoa seed producers. Samples were collected for a period of one year duration.

Methodology: Sterilized cocoa seeds were plated on potato Dextrose Agar and Sabourard Dextrose agar after which toxigenic strains were inoculated on Czapek Yeast Extract Agar and the resulting culture homogenized and spotted on TLC plate for viewing. Suspected ochratoxin A producers were inoculated separately on sterile cocoa bean seeds for 21 days after which OTA extraction were done and quantified using HPLC.

Results: Fourteen Aspergilli were isolated and identified. Twelve in Ikpenmen, eleven in Akure while the last seven were isolated from samples collected in Idanre. Aspergillus alutaceus were only isolated from Ikpenmen for the 12 months. Aspergillus ochraceus, A. niger, A. niger aggregate, A. carbonarius, A. aculeatus, A terreus, A vesicolor all produced OTA at varying concentration. A. ochraceus isolated from Ikpenmen samples produced the highest amount of OTA (372 µg/kg) while samples infested with A. niger aggregate from Akure alone produced OTA 109 µg/kg. A. carbonarius from all collection venues produced ochratoxin A OTA produced in Oba-Akoko by specie A. carbonarius had the highest value of 539 µg/kg culture.

Conclusion: The study showed that Aspergillus ochraceus, A. niger, A. niger aggregate, A. carbonarius, A. aculeatus, A terreus, A vesicolor were the major OTA producers contaminating stored cocoa produce in Ondo State, Nigeria.