A litmus milk test employs a specific medium containing skim milk and the pH indicator azolitmin. This medium allows for observation of various metabolic activities of bacteria, such as lactose fermentation, litmus reduction, casein coagulation, and casein hydrolysis. For example, acid production from lactose fermentation changes the medium’s color from purple to pink, while complete reduction of litmus manifests as a white color. The formation of a firm clot, a soft curd, or the digestion of casein provides further insights into the bacterial species’ capabilities.
This test offers a simple yet effective method for differentiating and identifying microorganisms, particularly those relevant to food microbiology and clinical settings. Its historical significance stems from its ease of use and the breadth of information it provides about bacterial metabolism, contributing significantly to early bacteriological studies. The distinctive reactions observable in litmus milk provide a quick and valuable initial step in bacterial identification, streamlining further diagnostic procedures.
