Mycotoxin formation in moist wheat under controlled temperatures.

Abstract

One-kilogram parcels of wheat with 20.5% moisture content were maintained at 15 degrees and 22 degrees C for 10 weeks to study quality changes. Temperature, moisture, oxygen and carbon dioxide levels, microflora incidence and abundance, seed germination, fat acidity values, aflatoxins, sterigmatocystin, ochratoxin A, penicillic acid, citrinin and zearalenone were monitored. By two weeks, trace levels of ochratoxin had formed at both temperatures. By 10 weeks, the wheat contained at least three times more ochratoxin A at 22 degrees C than at 15 degrees C. Strains of Penicillium verrucosum var. cyclopium were associated with ochratoxin A production. No other mycotoxins were detected. The effect of temperature was significant for all variables (greater effect at 22 degree C) except A. glaucus gr. and Penicillium (P less than .01). The effect of time was significant for all variables except bacteria (P less than .01). The shape of the response was fully characterized by the linear and quadratic terms, except for % moisture which was linear only, and for bacteria for which time was not significant. The interaction between time and temperature was significant (P less than .01) for total fungal propagule count, % moisture, and Aspergillus versicolor, indicative of the steeper rise in slope for 22 degrees C.