Ochratoxin A-producing Aspergilli in Vietnamese green coffee beans

Abstract

Aims: To determine the incidence and severity of infection by ochratoxin A (OA)-producing fungi in Vietnamese green coffee beans.

Methods and results: Aspergillus carbonarius, A. niger and yellow Aspergilli (A. ochraceus and related species in section Circumdati) were isolated by direct plating of surface-disinfected Robusta (65 samples) and Arabica (11 samples) coffee beans from southern and central Vietnam. Significantly, more Robusta than Arabica beans were infected by fungi. Aspergillus niger infected 89% of Robusta beans, whereas A. carbonarius and yellow Aspergilli each infected 12-14% of beans. OA was not produced by A. niger (98 isolates) or A. ochraceus (77 isolates), but was detected in 110 of 113 isolates of A. carbonarius, 10 isolates of A. westerdijkiae and one isolate of A. steynii. The maximum OA observed in samples severely infected with toxigenic species was 1.8 microg kg(-1); however, no relationship between extent of infection and OA contamination was observed.

Conclusions: Aspergillus niger is the dominant species infecting Vietnamese coffee beans, yet A. carbonarius is the likely source of OA contamination.

Significance and impact of study: Vietnamese green coffee beans were more severely infected with fungi than the levels reported for beans from other parts of the world, yet OA contamination appears to be infrequent.