(494g) The Use of Real-Time PCR to Determine the Growth Kinetics of Fungal Biomass On Solid Food At Different Water Activities

Fungal growth on solid foods usually make them unfit for human consumption but certain specialty foods require fungi to produce their characteristic properties. In either case, a reliable way of measuring biomass is needed in order to monitor fungal growth rates on these substrates and determine how they are affected by various factors such as water activity. In this study, the use of the species-specific real-time polymerase chain reaction (rt-PCR) to quantify the DNA of a target fungus and then relate this to its biomass was investigated. The developed procedure was utilized to determine the growth kinetic parameters of fungi growing on solid food. The advantage of this method is that fungal growth can be measured even with extensive substrate infiltration and that the growth rates of individual species in the presence of other fungi can be also be obtained. In this method, the ratio of the amount of DNA to biomass is a crucial parameter for converting the quantified DNA to biomass so the effects of the fungal species and age of colony on this ratio were studied. The test fungi used were Aspergillus niger and Penicillium chrysogenum which are species commonly involved in food spoilage. The kinetic parameters of the growth of these fungi on food were measured at different water activities. This method would be useful in determining the minimum water activity that will allow the growth of specific fungi on foods.