If fat is present, a mixture of ethanol and water becomes cloudy white in colour .
The cloudiness observed in a mixture of ethanol and water in the presence of fat stems from the fundamental principle that like dissolves like.
Fat, being hydrophobic or water-insoluble, tends to aggregate in the ethanol, which is a non-polar solvent.
When introduced to a water-based solution, such as milk, the fat forms tiny droplets that are suspended throughout the liquid due to their inability to dissolve in water.
The cloudiness arises from the light-scattering properties of these suspended fat droplets.
The dispersed fat particles disturb the passage of light through the mixture, leading to the appearance of a cloudy white color.
This phenomenon is not unique to fats and can occur with other non-polar substances like oil and wax.
In food analysis, this test serves as a quick and simple method to detect the presence of lipid-based components, providing a qualitative assessment of the sample's fat content.
However, it is crucial to acknowledge its lack of specificity, as other substances with similar solubility characteristics can yield comparable results.
Despite its limitations, this test remains a valuable tool in preliminary screenings for the presence of lipids in various food products.