Cryophilic Organisms in Water and Butter

Abstract

Samples of water from Minnesota and Wisconsin creameries and butter samples showing typical bacterial spoilage defects were plated on 2 differential media for total, lipolytic, and caseolytic counts. Incubation was at 37[degree], 20[degree], and 8[degree]C for 2, 5, and 7 days, respectively. Results indicated that 37[degree] incubation was inadequate for evaluation of bacterial flora and 8 [degree] incubation gave high counts in a number of instances. 41 caseolytic and lipolytic cultures capable of vigorous growth at 8[degree]C were isolated and identified as follows: 28 belonged to the genus Pseudomonas, 6 to Alcaligenes, 5 to Flavobacterium. One was classed as an Achromobacter, and one was a non-lactose-fermenting yeast. Incubation studies using sterile cream as a substrate indicated the ability of a majority of these cultures to cause extensive deterioration. In addition, the effect of 5 pure cultures on sterile cream and skim milk was measured quantitatively and qualitatively using acidity and formol titrations and tests for sulfur-containing compounds in the distillates from the cultured substrates. The intensity of defect as measured by odor production was not correlated with extensive protein deterioration. More severe deterioration was produced in cream than in skim milk. Positive tests for the presence of H2S and mercaptans were obtained in the process of distilling several cream cultures.