Effect of interacting environmental factors on growth and temporal mycotoxin production by Alternaria alternata on soybean-extract agar.

RAMIREZ M.L.; OVIEDO M.S; CHULZE S.N.

Key West, Florida

Workshop; 2007 Workshop Of International Commission on Food Mycology; 2007

International Commission on Food Mycology

The objective of this study was to determine the effects of water activity (aW; 0.995-0.90), temperature (18 and 25 °C), time of incubation (7-35 days) and their interactions on mycelial growth and mycotoxin production (alternariol (AOH) alternariol monomethyl ether (AME) and tenuazonic acid (TeA)) on 2% soybean extract agar by two strains of A. alternata isolated from soybeans in Argentina. Optimal aW levels for growth were in the range 0.995-0.94 with an optimum temperature of 25°C. Maximum growth rates were obtained at the highest aW (0.995) and 25°C with growth decreasing as the water availability of the medium was reduced. Both strains were able to growth at the lowest aW assayed (0.90). Greatest production of all three mycotoxins occurred at 0.98 aW and 25 ºC. The three mycotoxins were produced most rapidly after 7 days only at 25oC and 0.995 aw. All other conditions required 7-14 days before the toxins were produced. Maximum amounts of all toxins were produced at the 0.98 aW treatment after three weeks at 25°C for both strains. Production of AOH, AME and TeA occurred over a narrower range of aW (0.995-0.94) than that for growth (0.995-0.90). Two dimensional contour maps of aw x temperature profiles were developed from these data to identify areas where conditions indicate a significant risk from  these three mycotoxin accu