What method is used to detect if water has been added to milk?

The method used to detect if water has been added to milk is the freezing point test. This is based on the principle that pure milk has a specific freezing point, which is lower than that of pure water because milk contains sugars, proteins, fats, and other solutes. When water is added to milk, the freezing point of the mixture will rise closer to the freezing point of pure water, which is approximately 0 degrees Celsius. Therefore, by measuring the freezing point of the milk sample, one can determine the extent to which water has been added. A significant increase in the freezing point compared to standard values indicates adulteration with water.

While pH testing, viscosity measurement, and density comparison can provide useful information about milk quality and composition, they are not definitive for detecting the addition of water. For instance, pH levels can remain relatively stable in milk even when water is added, and viscosity is influenced by factors like fat content rather than just water presence. Density comparison may reveal changes, yet it is less sensitive and specific compared to the freezing point method, making the freezing point test a more reliable choice for detecting added water in milk.