Influence of water activity on Penicillium citrinum growth and kinetics of citrinin accumulation in wheat

The influence of water activity (a(w)) on both Penicillium citrinum growth and citrinin accumulation in wheat was studied. Wheat conditioned at different levels of a(w) and inoculated with a citrinin producer strain was incubated at 30 degrees C for 2 months. Fungal growth was assessed by microscopic examination. P. citrinum grew down to a(w) 0.775. Citrinin was not detected in the substrate at a(w) 0.800 and lower. As a(w) increased the toxin was detected earlier and the maximum accumulation increased markedly (65 mu g/kg at a(w) 0.810, 460 mu g/kg at a(w) 0.825 and 22 mg/kg at a(w) 0.885). Citrinin concentration declines rapidly after reaching the maximum at each a(w), level. (C) 1998 Elsevier Science B.V.