#32 Food test 3 - Emulsion (ethanol) test for Fats
This test is done to show the presence of lipids in a substance. The substance is first dissolved in ethanol. This solution is then dissolved in water. If lipids are present in the mixture, it will precipitates and forms an emulsion.
- Add the food sample to 2 cm3 of ethanol, shake well.
- Allow to settle in a test tube rack for 2 minutes for food to dissolve in ethanol.
- Empty any clear liquid into a test tube containing 2 cm3 of distilled H2O.
- A MILKY-WHITE EMULSION is a positive result: lipid is present.
- If the mixture remains clear, there are no fats present in the sample
- Lipids are insoluble in water and soluble in ethanol (an alcohol).
- After lipids have been dissolved in ethanol and then added to H2O, they will form tiny dispersed droplets in the water. This is called an emulsion.
- These droplets scatter light as it passes through the water so it appears white and cloudy.