Effect of Water Activity on Disappearance of Patulin and Citrinin From Grains

Sterile, ground barley, corn and wheat were adjusted to different water activities (a w ) and intentionally contaminated with patulin and citrinin. Samples were incubated at 25°C at a relative humidity in equilibrium with their a w . Toxin levels were determined by thin‐layer chromatography (TLC) after different periods of incubation. Disappearance rates were greater in substrates with a higher a w . At a w = 0.70, estimates of half‐lives for patulin in barley, corn, and wheat were 12.7, 4.4 and 4.4 days, respectively; at an a w of 0.90, they were 6.8, 2.4 and 1.9 days. For citrinin, these values were 7.8, 15.5 and 11.9 days at a w = 0.70, and 1.8, 10.4 and 3.0 days at a w = 0.90. Because of these short half‐lives, grains that were responsible for a mycotoxicosis may, at the time of analysis, contain only low levels of these toxins.