Rapid enumeration of clostridial spores in raw milk samples using an impedimetric method

Abstract

Late spoilage of cheese is due to gas formation during lactic acid fermentation by spore-forming, gram-positive, anaerobic clostridia of the species Clostridium tyrobutyricum, Clostridium butyricum and Clostridium sporogenes. Since small numbers of such clostridial spores readily cause considerable losses in cheese production, spore numbers of fewer than 100 spores/liter must be determined reliably. Until recently, the only reliable method available was the time-consuming (7 days) and cumbersome Most Probable Number Method (MPN). The objective of this study was to examine the feasibility of using impedance technology as an alternative method for the enumeration of clostridial spores. Three to fifteen replicates of 7.5-12.0 mL samples were tested using an impedimetric method with and without the addition of Oxyrase to generate anaerobic conditions within the impedance measurement cells. Results were obtained in less than 48 h. Data derived from the rapid impedance method were statistically comparable to those obtained using the reference method (MPN).