Rapid Enumeration of Bacteria in Heat‐treated Milk and Milk Products Using a Membrane Filtration‐Epifluorescent Microscopy Technique

Abstract

A rapid direct epifluorescent filter technique (DEFT), taking ca. 20 min to complete, was used to enumerate bacteria in heat‐treated milk and milk‐products. The DEFT count could detect as few as 5750 bacteria/ml in pasteurized and skim milk, pasteurized cream, whey and sweet cream butter and was in agreement with the standard plate count. The technique was also used to determine the sterility of cartoned ultra heat‐treated milk after incubation at 37°C. The agreement between the DEFT and plate count was poor for evaporated and condensed milks, some reconstituted skim milk powders, pasteurized whey and ripened cream butter. Possible reasons for this are discussed.