23 December 2012

#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.
  • 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.

Additional source: cccmkc.edu.hk
                             Brilliant Biology Student  


  1. Does this experiment has any errors ?

  2. Why are there oil drops if the fat is already dissolved in ethanol?

    1. The ethanol is soluble in the water.
      The ethanol contains dissolved lipids.
      When the ethanol dissolves in water, the fats will separate as they are not soluble in the water.

    2. when water is added to the ethanol with dissolved lipids the ethanol dissolves in water since it is soluble in water leaving the fats suspending.hope this will help

  3. i think that is too concise for me .... wasnt this suppose to help me write my own

  4. Thx, it is really very simple, if anyone needs any help on the fat test or any of the othee protein, sugar or starch in food test then please comment and I am ready to give help.

  5. After being dissolved solubley in ethanol, how do fat globules form a layer in water??

  6. what if sodium hydroxide was used instead of water? what would be the result?

  7. So so useful read it was.Thanks for your great work.

  8. can some one send the full table