Preservative and Temperature Effect on Growth of Three Varieties of the Heat-Resistant Mold, Neosartorya fischeri, as Measured by an Impedimetric Method

The combined effects of inoculum amount, temperature, pH, and food preservatives on growth of three varieties of heat-resistant mold Neosartorya fischeri cultured on a fruit juice-like medium was investigated. JV. fischeri var. glabra growth occurred at 100 mg sodium benzoate/L at pH 3.5, a level that completely inhibited outgrowth of the other varieties. All were similarly affected by sulfur dioxide; completely inhibited by 300 mg/L at pH 3.5. The inhibitory effect of preservatives was strongly affected by pH, inoculum amount, and temperature. Growth was significantly delayed when temperature was decreased from 32 to 25 to 18°C or pH from 4.5 to 3.5. This is the first report on the use of impedance microbiology to study the effects of environmental factors on molds.