Incidence, level, and behavior of aflatoxins during coffee bean roasting and decaffeination

Abstract

Screening for aflatoxins (Afs), isolation and identification of Aspergillus flavus, and the effect of decaffeination and roasting on the level of contamination in coffee beans are studied. The percent frequency of A. flavus ranged between 4 and 80% in green coffee beans (GCB), whereas in ground roasted coffee beans (GRCB), it ranged between 1 and 71%. Aflatoxins were detected in 76.5 and 54.6% of the infected samples with averages of 4.28 and 2.85 μg/kg of GCB and GRCB, respectively. Roasting was demonstrated to lower the concentration of Afs in GCB. The Afs levels were reduced by ∼42.2-55.9% depending on the type and temperature of roasting. The highest yields of Afs were detected in the decaffeinated green coffee beans (24.29 μg/kg) and roasted coffee beans (16.00 μg/kg). The growth of A. flavus in liquid medium containing 1 or 2% caffeine was reduced by 50%, and the level of aflatoxin in the medium was undetectable.