To assess the effects of Fusarium infection on the polysaccharides of winter wheat grain (Triticum aestivum L.), grain samples obtained from plants artificially inoculated with Fusarium culmorum were analyzed. Microscopy revealed obvious damage to the starch granules in the seriously infected samples. The Fusarium infection had no analytically detectable influence on the starch and total insoluble dietary fiber content of the wheat grain. There were significantly positive relationships between alpha-amylase activity, cellulase activity, total soluble dietary fiber content, pentosan content, and degree of infection quantified by an enzyme-linked immunosorbant assay, which would indicate the importance of fungal enzymes. A distinct higher Hagberg falling number (FN) was determined in the seriously infected samples, while the viscosity and sucrose content of the flour decreased. However, the addition of a liquid medium contaminated with F. culmorum led to a significant decrease in the FN. Depending on the type of buffer used, the alpha-amylase of F. culmorum demonstrated its maximum activity between pH 5.5 and pH 7.0 at 30-50 degrees C. Remarkably, this fungal alpha-amylase showed a thermostable characteristic and was active over a wide range of temperatures, from 10 to 100 degrees C. This type of thermostability suggests that the alpha-amylase of F. culmorum may damage starch granules throughout the processing of wheat flour, thereby inducing weak dough properties and unsatisfactory bread quality.