Modeling of germination and growth of ochratoxigenic isolates of Aspergillus ochraceus as affected by water activity and temperature on a barley-based medium Original Research Article

Aspergillus ochraceus is an ochratoxin producing fungus that can be found on stored cereal grains such as barley. The objective of this study was to determine the effects of water activity (aw, 0.75–0.99) and temperature (10–30°C) on germination and growth on barley extract agar medium (BMEA) of three isolates of Aspergillus ochraceus. The three isolates showed an optimal aw for germination and growth of 0.99–0.95 at 20–30°C, with a marked increase of the lag phases and decrease of germination and growth rates at the marginal levels of aw and temperature assayed. Minimum level of aw for germination was 0.80 and 0.85 for growth. Data were then modeled by an MLR regression and response surface models were obtained. These models may allow a rough prediction of germination/growth as a function of the storage temperature and moisture content of barley grains.