In this A-Level Biology Lesson “Lipids: The Emulsion Test for the presence of Lipids”. 

You'll learn each of the steps involved in this common food test. You’ll need to be able to describe how and why each step in the emulsion test is done and how to interpret the results. 

When you’re happy you can write out a suitable method for the emulsion test and know what to expect you’re ready to download the and complete the accompanying lesson booklet. 

When you’ve answered the questions, check your answers with mine which are written out in full in the back, where you can compare your answers to see exactly how you should write them in a way that gains maximum marks in the exams and laboratory reports.

A-Level Biology "Lipids: The Emulsion Test"

​Here's a summary of the lesson: -

Lipids (fats and oils) are insoluble in water, but they do readily dissolve in ethanol. This property of dissolving fats in alcohol is the basis of the emulsion test.

If you're testing a food sample for the presence of lipid follow these steps.

Crush / grind the test sample and add to a test tube with ethanol

Gently mix the sample with the ethanol, ensure all lipid is dissolved in the ethanol.

Decant the dissolved liquid into another test tube containing water.

Observe the results.

A positive result will show a milky / white emulsion. 

In preparation for exam style questions on this topic, ensure you know why each step is performed. Understand also that a Bunsen burn is NOT needed for this procedure.