Influence of water activity and temperature on growth and mycotoxin production by Alternaria alternata on irradiated soya beans

OVIEDO, M.S.; RAMIREZ, M.L.; BARROS, G.; CHULZE, S.

INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY

ELSEVIER SCIENCE BV

Año: 2011 vol. 149 p. 127 - 132

0168-1605

The aim of this study was to determine the effects of water activity (aw) (0.99-0.90), temperature (15, 25 and 30 °C) and their interactions on growth and alternariol (AOH) and alternariol alternariol monomethyl ether (AME) production by Alternaria alternata on irradiated soybean seeds. Maximum growth rates were obtained at 0.980 aW and 25°C. Minimum aW level for growth was dependant of the temperature evaluated. Both strains were able to growth at the lowest aW assayed (0.90). Maximum amount of AOH was produced at 0.98 aW but at different temperatures 15 and 25 °C for the strains RC 21 and RC 39 respectively. Maximum AME production was obtained at 0.98 aW and 30 ºC for both strains. The concentrations range of both toxins varied considerably depending on aW and temperature interactions assayed. Further, the two metabolites were produced over the temperature range from 15 to 30 ºC and aW range from 0.99 to 0.96. The limiting aw for detectable mycotoxin production is slightly greater than that for growth. Two-dimensional profiles of aW x temperature were developed from these data to identify areas where conditions indicate a significant risk from AOH and AME accumulation on soybean. The knowledge of AOH and AME production under marginal or sub-optimal temperature and aW conditions for growth can be important since improper storage conditions accompanied by elevated temperature and moisture content in the grain can favour further mycotoxin production and lead to reduction in grain quality and also could present a hazard if the grain is used for human consumption or animal feedstuff.