Ochratoxin A-producing Aspergilli in Vietnamese green coffee beans

The definitive version is available at www.blackwell-synergy.comAims: 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 μg 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.S.L. Leong, L.T. Hien, T.V. An, N.T. Trang, A.D. Hocking, E.S. Scot

Aspergillus species producing ochratoxin A: isolation from vineyard soils and infection of Semillon bunches in Australia

The definitive version is available at www.blackwell-synergy.comAimsThe incidence of toxigenicity among Australian isolates of Aspergillus niger and Aspergillus carbonarius was assessed. Aspergillus rot and concomitant production of ochratoxin A (OA) in bunches inoculated with A. carbonarius were also investigated.Methods and resultsAspergillus niger and A. carbonarius were isolated from vineyard soils. Aspergillus niger was more widespread than A. carbonarius, and two restriction fragment length polymorphism types of A. niger, N and T, were present. Three of 113 A. niger isolates and all 33 A. carbonarius isolates produced OA. Aspergillus carbonarius was inoculated onto Semillon bunches with and without damage in the month before harvest. Damaged berries at greater than 12.3 (o) Bx were particularly susceptible to Aspergillus rot and production of OA, which was concentrated in severely mouldy berries.ConclusionsOA in Australian grapes results mainly from infection of berries by A. carbonarius. It is concentrated in discoloured, shrivelled berries. The potential for Aspergillus rot and OA production appears to commence after veraison and increase with berry damage and ripeness.Significance and impact of the studyMinimizing damage to grapes between veraison and harvest significantly reduces Aspergillus rot and OA formation. Monitoring the extent of Aspergillus rot in bunches infected with toxigenic Aspergillus spp. may give some indication of OA contamination