Aflatoxin Contamination of Red and Black Beans (Phaseolus vulgarism L.) in Costa Rica.

The Mycotoxin Laboratory at CIGRAS collaborates with the Costa Rican State Phytosanitary Service (SFE) to monitor aflatoxin levels in imported agricultural commodities and with industry partners in order to assure quality control. Based on results for aflatoxin analyses conducted from 2003 to 2015, it was observed that red beans (Phaseolus vulgaris L.) had higher aflatoxin levels than black beans. Therefore, the objective of the current study was to determine the level of aflatoxin contamination of two black bean varieties (Guaymi and Matambú), two red bean varieties (Cabécar and Tayni), and a white bean variety (Surú) inoculated with Aspergillus flavus, in order to better understand the role of bean type in the risk of mycotoxin contamination. Treatments consisted of the 5 varieties previously mentioned, as well as seed coat removal (e.g., with and without the seed coat). Twenty-five grams of seeds of each treatment were placed in 125 ml Erlenmeyer flasks, autoclaved, and inoculated with 2 ml of a 1x10⁷ spore solution. Flasks were placed in an incubator at 28^oC and a 12 h photoperiod for 22 days.  Three flasks per treatment were used to make a composite sample to determine aflatoxin levels. Total aflatoxin contamination was measured using the AOAC method 991.31 (A-G).  The experiment was replicated two times. Results showed that the A. flavus isolate used in this experiment could produce aflatoxins in concentrations greater than 150 ug kg^-1, however, the ability of A. flavus to produce toxins was independent of the bean variety and the presence or absence of the seed coat. Based on these results, further research is required in order to determine how and when beans can be contaminated with aflatoxins in order to determine if bean type can be considered an important risk factor.