Differential Production of Aflatoxin on Natural and Heat-Treated Cocoa Beans

Abstract

Costa Rican-type cocoa beans were tested as a substrate for two known aflatoxigenic fungal species, Aspergillus flavus NRRL 3251 and Aspergillus parasiticus NRRL 2999. Natural floral growth in both cooked (autoclaved) and raw cultures failed to show aspergilli and aflatoxin as analyzed by thin layer chromatography. Raw, ground cocoa bean medium inoculated with both species of aspergilli had mycelial growth, sporulation, but no detectable levels of aflatoxin. Similarly treated but cooked (autoclaved) cocoa medium also provided for mycelial growth, and sporulation, but total aflatoxin levels were 388.1 μg/g of substrate for the A. parasiticus cultures and 2.2 μg/g of substrate for the A. flavus cultures. The general results appear to support the low level of a limited number of reports of toxin contamination in natural cocoa. The simplified extraction methods used herein provided results similar to other methods.