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Cryophilic Organisms in Water and Butter

Division of Dairy Husbandry, University of Minnesota

ABSTRACT

1. In plating out creamery water samples and butter samples on two differential media, it was found that 20° C. incubation gave, in most cases, the highest counts. However, 8° C. incubation yielded counts that were of considerable magnitude. In no sample did 37° C. incubation produce maximum total counts.
   
2. Caseolytic and lipolytic cultures capable of vigorous growth at 8° C. were isolated and purified. Of the forty-one cultures studied, twenty-eight belonged to the genus Pseudomonas, five to the genus Flavobacterium, six were species of Alcaligenes, one was classified as an Achromobacter, and one was a non-lactose-fermenting yeast.
   
3. Incubation studies using sterile cream inoculated with pure cultures showed that a large majority of these cultures were capable of causing extensive deterioration as measured by odor production. The production of odor defects typical of each culture depended on the temperature and the time of incubation.
   
4. The effect of five pure cultures on cream and skim milk was observed organoleptically and measured by acidity and formol titration. It was found that the intensity of the odor production was not correlated with extensive protein deterioration, as measured by the formol titration. It was also observed that odor production was more intense in cream than in skim milk. Positive qualitative tests for hydrogen sulfide and the presence of mercaptans were obtained during the process of distillation of several of the cultured cream samples.
   

¹ Taken from data presented in a thesis submitted to the Graduate Faculty of the University of Minnesota by J. J. Jezeski in partial fulfillment of the requirements for the degree of Master of Science. Scientific Journal Series, Paper No. 2290, Minnesota Agricultural Experiment Station.