SOME FACTORS WHICH CONTRIBUTE TO THE PSYCHROPHILIC BACTERIAL COUNT IN MARKET MILK*

Abstract

Results indicate the mesophilic counts were approximately three times greater than the psychrophilic counts in raw milk. No psychrophilies were ever found in 4.1 ml of pasteurized milk taken from the vat (LTLT) or from the HTST pasteurization system. Psychrophiles were found in some of the bottled milk, taken at the start of bottling operations. Psychrophiles were found in all samples at the end of one week storage at refrigeration temperatures, and almost invariably the psychrophilic count at this time was higher than the mesophilic count. Results indicate the psychrophilic bacteria were not thermoduric and probably were facultative rather than true psychrophiles. They were mostly cocci or non-spore forming bacilli, inert or acid forming.