Impedance microbiology: Applications in food hygiene

Impedance microbiology is a rapid method that enables qualitative and quant itative tracing of microorganisms by measuring the change in the electrical conductivity. With direct impedance technology, the change in the conducti vity of a liquid culture medium serves as a measuring parameter, whereas wi th indirect impediometry, the change in the electrical conductivity of a re action solution, which occurs through the absorption of gases from the inoc ulated bacterial culture, is measured. Most investigations concerning the a pplicability of impediometry in food microbiology deal with the impedimetri c detection or enumeration of Enterobacteriaceae, especially the detection of Salmonella. However, impediometry has been applied to other bacterial gr oups or species as well. Furthermore, a great number of published findings concern the impedimetric determination of the total bacterial count. The su ccessful application of this fast method on further areas of food hygiene, such as tracing antibiotics and testing additives for their antimicrobiolog ical effect, has also been described. in general the use of impediometry fo r the application areas stated has been judged positively. However, the tim e and expense required by the user to optimize the method, the deficits whe n testing slightly contaminated sample material or determining the bacteria l count in those cases in which the microorganisms are sublethally damaged, and the necessity of performing individual calibration for each food categ ory limit the applicability of impediometry.