Studies on the refrigerated storage of wheat (Triticum aestivum). 2. Ergosterol, xanthomegnin, viomellein and brevianamide A after inoculation with Penicillium viridicatum.

Abstract

Wheat seed was adjusted to 18, 20, 22, 24 and 26% moisture content (m.c.), and stored for 240 days at 4 or 10 degrees C following inoculation with a strain of Penicillium viridicatum producing the toxins, xanthomegnin (XA), viomellein (VIO), and brevianamide A (BA). Wheat kernels were not sterilized before inoculation. The concentration of ergosterol (ERG), a chemical indicator of fungal biomass, remained constant at 18% m.c./4 degrees C, but increased under the other conditions. The time before a detectable increase of ERG concentration was higher and the rate of ERG production lower with decreasing moisture content and temperature. XA and BA were produced at both temperatures at 20-26% m.c., VIO was produced at 22-26% m.c./4 degrees C and 20-26% m.c./10 degrees C. The results suggest or indicate that the onset of XA, VIO and BA production (detection limits: 10, 15, and 0.1 micrograms/kg, respectively) coincided with the onset of ERG production. Maximum toxin contents were lower with decreasing moisture content at both temperatures, but were similar at 4 and 10 degrees C at 22-26% m.c. It is concluded that wheat contaminated with P. viridicatum should not be stored beyond the onset of ergosterol production; maximum storage periods are recommended.