Ethanol Emulsion Test

For illustrative purposes. Not actual image of my results.

Task: Find out if lipids are present in given food samples.

Method:

1. Take a clean and grease-free test tube.

2. If food sample is dry, grind it up in water.

3. To 2 cm3 of the sample, add 5 cm3 of ethanol.

4. Shake the tube gently, but thoroughly to dissolve any lipids in the sample.

5. Add 5 cm3 of water and shake gently.

6. A cloudy-white colour indicates the presence of a lipid.

7. As a control, repeat the method using water instead of the sample, final solution should remain clear.

Results:

food sample - colour of emulsion

biscuit - cloudy-yellow

vegetable oil - very cloudy-white

marshmallow - slightly cloudy

Conclusion: Out of these three samples, vegetable oil contains the most lipids. It was difficult to determine the presence of lipids in the other food samples because of their consistency. Even after grinding the dry food up with water, there was still some very small parts of food floating in the solution, which made it hard to see if the cloudiness is caused by the actual presence of lipids or the debris. This test also did not provide us objective information about the amount of lipids present, so to find that out I would do a quantitative test, like the determination of iodine number.