Comparative studies of Ochratoxin A (OTA) production by Aspergillus niger, Aspergillus ochraceus and Penicillium nordicum in Cocoa, Coffee and yeast extract sucrose agar

Abstract

The study aims to investigate the concentration of ochratoxin A (OTA) produced in dry cocoa beans by Aspergillus ochraceus, A. niger and Penicillium nordicum over a period of twenty-four days on three growth substrates of Yeast Extract Sucrose Agar (YES), Coffee and Cocoa agar. Quantitative analysis of OTA contamination in the samples was determined with a validated High Performance Thin Layer Chromatography (HPTLC) method with fluorescence detection by extraction with a mixture of 1.0 ml Dichloromethane and 1.0 ml of 1 % Acetic acid solution. OTA production by Aspergillus ochraceus in YES and Coffee media was high and more than observed in the Cocoa media. Highest levels of OTA produced during the growth of A. ochraceus in YES, Coffee and Cocoa media were 6.23, 8.09 and 2.29 ppm and occurred on day 23, 19 and 11 respectively. Although A. niger produced low levels of OTA in all the three media, YES and Coffee media were observed to support higher OTA production than Cocoa media. Maximum OTA concentration observed in YES media was 3.12 ppm on day 22. For Coffee media, 3.60 ppm occurred on day 15, while in Cocoa media 3.10 ppm was recorded on day 23. The production of OTA by P. nordicum showed the same trend with higher levels observed using YES and Coffee media, as compared with Cocoa media. Maximum levels of OTA produced during the growth of P. nordicum in YES, Coffee and Cocoa media were 8.16, 8.96 and 0.84 ppm and occurred on day 7, 19 and 12 respectively. Cocoa substrate is not suitable to OTA production by A. ochreaceus as compared to YES and Coffee media which are more suitable to OTA production by A. niger and P. nordicum