Invertase production of common storage moulds in food and feed grains as a possibility for rapid detection of aspergillus flavus group and Aspergillus fumigatus

Invertase production of grain storage moulds was studied. Aspergillus spp. and Penicillium spp. were grown in a sucrose based liquid medium, at 37°C. The A. flavus group (A. flavus, A. parasiticus, A. nomius, A. oryzae) and A. fumigatus showed a fast growth and intense invertase activity, while other Aspergillus spp. and Penicillium spp. grew slower and produced less invertase. The pattern of accumulated reducing sugar after 20 and 48 h of incubation was characteristic to the species studied. From inoculation studies the detection limit was calculated as: 1–10 conidia of A. flavus group and A. fumigatus, as compared to 103–104 for the other species studied. The method may be recommended as a rapid test for the detection of A. flavus group and A. fumigatus in food and feed grains.