Effect of variety, locality and processing of coffee beans on the detection and determination of aflatoxins

ABSTRACT

The effect of variety [Arabica and Robusta], locality of cultivation [Brazilian, Ethiopian and Colombian] of the same variety [Arabica] and processing [decaffeination and roasting] on the detection and determination of aflatoxins in coffee beans were studied. Using the AOAC method for the detection of aflatoxins in green coffice beans could not succeed to overcome the masked material that covered AFB[2], G[1] and G[2] in all samples under study and AFB[1] was the only spot that appeared on the TLC. Due to roasting of coffee beans, the interference material with aflatoxins increased and even AFB[1] could not be detected by the AOAC method. An improved procedure which uses silver nitrate to get rid of caffeine and related compounds, succeeded to remove the interference materials due to the coffee beans matrix and aflatoxins spots were separated clearly. However, this method failed to remove the interference materials that masked the area of aflatoxins in roasted coffee beans completely. HPLC was tested as an alternative technique for the detection of aflatoxins. The HPLC chromatogram of green coffee beans using the AOAC method showed unidentified intensity peaks and low recovery was obtained. The HPLC coupled with the improved procedure of extraction showed that the unidentified peaks due to the matrix of green and decaffeinated coffee beans were eliminated. However, it failed to overcome the problems of the roasted coffee beans especially in the area of AFG[1]. An obvious effect of cultivation locality on the matrix of green coffee beans was observed. This effect also appeared in the recovery percentage of aflatoxins. Also, this locality effect did not allow to reach a solid conclusion for the effect of variety