Early detection of fungi in stored grain

Abstract

Accurate and reliable measurement of the activity of fungi in grain is necessary to enable effective management of storages to be undertaken and to prevent loss in grain quality. In the past guidelines for safe storage times and stability have been based on the wholly inadequate criterion of the presence of visible mould. Traditionally, direct plating of whole grains on to agar or the plating of grain washings or homogenised grain on selective media have been used as an indicator of grain quality. However, these methods are labour intensive and require long periods of time to obtain results. A number of other methods have been explored to try and detect the activity of spoilage fungi prior to the presence of visible mould. They can be divided into those which quantify the total fungal biomass and those which enable individual species to be differentiated. The former have involved the analysis of biochemical markers characteristic of fungi, including chitin, ergosterol and ATP; the quantification of enzymes indicative of fungal invasion; presence of odours, and electrochemical methods. The latter has involved the use of DNA probes and the development of monoclonal antibodies to specific spoilage fungi. This paper will consider some of the above methods being used and describe work on the effect of water availability on the relationship between ergosterol and fungal activity and enzyme activity in cereal grain prior to visible moulding.