A new indirect impedancemeter to detect microbial contaminations in agro-food industry.

The impedancemetry method can be used in Microbiology to perform the detection, quantification and even identification of some bacteria. Basic knowledge about this subject can be stated from Ur and Brown (1975), Firstenberg-Eden and Eden (1984), the reviews of Silley and Forsythe (1996), and Wawerla et al. (1999). With Escherichia coli, Bacillus subtilis and Saccharomyces cerevisiae cultures, the conductimetric responses were highly replicable, and repeatable for inocula concentrations from 1 to 10(8) CFU mL(-1). The main use of such devices could be the detection of contaminations of foodstuff. Several of these foodstuffs incubated at 37 degrees C spontaneously release quite large amounts of CO2. Our impedancemeter, however, was able to detect an Escherichia coli presence in canned French beans down to 2.35 10(-2) colony forming units (CFU) mL(-1), and a Saccharomyces cerevisae contamination of apple purée in glass jars down to 6.1 10(-3) CFU mL(-1).