What does Litmus Milk test for?

The Litmus Milk test is primarily used to assess the fermentation of lactose and the production of caseinase by microorganisms. In this medium, lactose serves as a carbohydrate source, and casein, which is the primary protein in milk, can be utilized by certain bacteria.

When a microorganism ferments lactose, it produces acid, which will lead to a decrease in pH, resulting in a color change of the litmus indicator in the medium to pink. This indicates that lactose has been fermented. Additionally, some bacteria produce caseinase, an enzyme that breaks down casein into smaller peptides or amino acids, resulting in the clearing of the milk, which is indicative of protein metabolism.

This test provides a dual assessment: Firstly, of acid production (lactose fermentation) and secondly, casein utilization (caseinase production). The other options do not relate to the primary functions of the Litmus Milk test. For instance, while the reduction of oxygen is important for assessing anaerobic bacteria, it does not apply to this particular test. Similarly, lipase activity pertains to the breakdown of fats, and starch hydrolysis focuses on the breakdown of carbohydrates like starch. Neither of these processes is involved in the Litmus Milk test.