Estimation of coliform bacteria ice cream by use of the membrane filter.

The usual methods employed for the estimation of coliform organisms (American Plublic Health Association, 1953) are based on the use of differential media whose selectivity depends, in part, on the presence of lactose as the sole fermentable carbohydrate. In the case of determinations conducted on ice cream samples, which normally contain an appreciable concentration of sucrose, the desired selectivity is lost and false-positive results may be obtained (American Public Health Association, 1953). In theory, the bacteriological membrane filter (Clark et al., 1951) offered a techni(ue for the removal of soluble carbohydrate from the microbial flora prior to contact between the flora and the selective medium. It thus seemed reasonable that a direct method for the estimation of true coliform organisms in ice cream might be based on the use of this filter.