abstract |
A rapid method for detecting the presence or absence of coliform bacteria in a liquid or liquified dairy sample, for example, skimmed milk, lowfat milk, or whole milk. A growth medium containing a fluorogenic substrate is combined with the dairy sample and is incubated for a brief period of time, for example for about 4 hours, after which a first fluorescence value of 4-methylumbelliferone is measured. The dairy sample is incubated again for about 2-8 hours after which a second fluorescence value of 4-methylumbelliferone is measured. Total, fecal, or thermotolerant coliform bacteria are determined to be present in the sample if the second fluorescent value exceeds the first fluorescent value by a predetermined 4-methylumbelliferone concentration threshold. |