Amperometric monitoring of bacteria-induced milk acidity using a platinum disc microelectrode.

The acidity induced by the action of bacteria in milk samples was monitored amperometrically by using a platinum microelectrode. The measurements were performed directly on commercial packs of milk, stored at 32 degrees C, and were continued for 9-10 d after inoculation. The data were compared with those obtained by measuring the pH of the samples and the results are discussed on the basis of the metabolism of each bacterial species. The effects of the following bacteria were examined: Staphylococcus aureus, Bacillus cereus, Streptococcus faecalis, Bacillus subtilis, Aeromonas, and Corynebacterium.