Fusarium graminearum Colors and Deoxynivalenol Synthesis at Different Water Activity

Deoxynivalenol (DON) is a well-known mycotoxin, responsible for outbreaks of gastrointestinal disorders in Japan. Fusarium graminearum, a parasite of cereal crops, produces this toxin and this is one of the reasons why it is important to understand its metabolism. It is possible to predict the mold's color change and the quantity of DON synthesized throughout its lifecycle. Furthermore, a(w) has been found to affect the amount of DON. This study aimed to analyze the potential of F. graminearum surface color as a predictor of DON concentration at a(w) = 0.94, 0.97, and 0.99. Thus, 36 specimens were incubated at 25 degrees C, 12 at each a(w). After 4, 8, 12, and 16 days, three specimens from each a(w) were collected for color analysis and DON quantification. For color analysis, photos were taken and red, green and blue (RGB) channels were measured on ImageJ software. DON was quantified through liquid chromatography (HPLC). Color changes were only observed at a(w) = 0.99 because at lower a(w) the molds presented high growth of white mycelium. Yet, DON increased in all cases. It was only possible to relate the colors with DON concentration at a(w) = 0.99, where they presented inverse proportionality.