The application of a rapid simple test for quantitation of coliforms in milk and milk products
1999
Rogerson, A. (Immuno Chemical Products, Mount Albert (New Zealand))
With the increasing number of developments in the dairy industry, including new processes, packaging and products, there remains the need to ensure quality throughout the system. Testing for coliforms, an integral part of any quality assurance regime, has been associated with substantial delays between testing and the availability of results. As a consequence product has often been manufactured and packaged before the extent of coliform contamination is known. With this in mind, a Rapid Coliform Test (RCT ) has been developed for use in the dairy industry, which measures coliform contamination directly and has the advantages that it is as accurate as it is rapid. Based on the traditional resazurin test, RCT incorporates a growth medium specific for coliforms so that the presence of coliform contamination can be detected visually. Because the test system utilises a 100ml sample, the detection and enumeration of coliforms is both rapid and sensitive. Coliform organisms grow in the specific medium, metabolising lactose to lactic acid. This lowers the pH which, when accompanied by a shift in redox potential, induces a colour change in the resazurin. The blue to pink colour change is visual, requiring no instrumentation, although instruments are available which will quantitate the colour change. The rate at which the bacteria induce this colour change is proportional to the original number in the 100 ml sample. Thus by monitoring the time for the change to take place, the contamination can be quantified.
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