How can the sanitary condition of milk be assessed if large samples for bacteria examination cannot be collected?

The methylene blue reduction test and the resazurin test are effective methods for assessing the sanitary condition of milk, particularly when large samples cannot be collected for direct bacterial examination. These tests are based on the ability of bacteria present in the milk to reduce certain dyes, which indicates microbial activity.

In the methylene blue reduction test, milk is mixed with methylene blue dye and incubated. If bacteria are present, they will consume oxygen and reduce the dye, leading to a color change. The speed of this color change can help gauge the level of bacterial contamination; a faster reduction indicates higher bacterial levels, suggesting poor sanitary conditions.

Similarly, the resazurin test employs resazurin dye, which changes color in response to the reduction of oxygen due to bacterial growth. This test is sensitive to the presence of viable bacteria and effectively indicates the quality of the milk. If the color remains blue, the milk is generally considered to be of good quality.

These methods are advantageous because they are simple to perform, require minimal equipment, and provide results relatively quickly, making them practical choices for assessing the sanitary condition of milk in various settings.