Incidence and detection of thermotolerant and thermophilic fungi from maize with particular reference to Thermoascus species

A number of thermotolerant and thermophilic fungi were isolated from shipments of food-aid grain, and from large bag stacks of maize stored in sub-Saharan Africa. Thermotolerant fungi included Aspergillus candidus, A. fumigatus, A. flavus and Paecilomyces varioti; thermophilic fungi included Thermomyces lanuginosus, Rhizomucor pusillus, Thermoascus aurantiacus and T. crustaceous. Temperature profiles for Thermoascus spp. indicated that isolates of T. aurantiacus grew up to 60 °C, and T. crustaceous to 55 °C, whereas Paecilomyces could not grow above 50 °C. Thermoascus species isolated from grains conformed to published morphological descriptions. Problems associated with the detection and interpretation of fungal spoilage in relation to heat-damaged grain are discussed.