IMPEDANCE AS AN ALTERNATIVE TO MPN ENUMERATION OF COLIFORMS IN PASTEURIZED MILKS

Samples (900) of pasteurized whole, semi-skimmed and skimmed milk were subjected to conventional enumeration of coliforms bf a nine-tube mos t probable number (MPN) technique, and impedance enumeration, in paral lel. Regression analysis of the positive samples (98) showed that impe dance enumeration was at least as accurate as the MPN method but resul ts were obtained faster, with all testing being completed in 20 h, rat her than 48 h. Consumable requirements, and staffing levels, were also much less with the impedance system. The impedance method could there fore beneficially replace the conventional method.