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A total of 410 samples of 1995 corn from Kansas were analyzed for Fusarium moniliforme. One-hundred kernels of each were plated on Malt Salt Agar (MS6T) and incubated for 7 days at room temperature (20-24C). The type of fungal colonies present on each grain were identified and recorded. To distinguish Fusarium species, subcultures were grown on carnation leaf agar plates and incubated for 14 to 21 days at room temperature. Colony morphology, morphology of the conidia and conidiophores were compared for identification and confirmation to species. Fumonisin B level on the samples were determined using the immunoaffinity method (Fumonitest) from VICAM. Samples from dryland counties were highly infected by molds. Variety, cropping system (Dryland and Irrigated), and location significantly affected the level of infection. Among field fungi, Fusarium spp. and Acremonium spp. were most prevalent and widespread. Aspergillus species observed included A. flavus, A. niger, A. glaucus, and A. clavatus. F. moniliforme was the most abundant and frequently isolated Fusarium species. Samples of irrigated corn had the highest percentages of F. moniliforme. The rate of infection varied significantly (P usd\leusd 0.05) by location and variety. FB analysis showed differences between cropping systems, locations, and varieties. There was no correlation between FB level and the level of kernels invaded by of F. moniliforme. In other experiments sound yellow corn (US No. 2) was mixed with cultured, fumonisin containing corn to obtain a contamination level of 250 ppm of FB, then alkali-cooked to produce hydrolyzed fumonisin B. Alkali-cooked corn was subjected to extrusion at 170C using four different moisture contents (24, 27, 30, and 33%) and two circular dies (tapered and angular). Levels of FB and HFB in the extruded products were determined using High Performance Liquid Chromatography (HPLC) with ortho-phtaldialdehyde (OPA) derivatives. The steep water from the alkali-cooking process removed 37% of the initial fumonisin content from contaminated corn. The fumonisin remaining in the corn was present mainly as HFB form. Extrusion reduced the recoverable HFB content by as much as to 67%, and FB was not detected in the extruded product. Moisture content of the material to be extruded and the die geometry affected the reduction of recoverable fumonisin.
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