Fats and Protein Tests

A series of free Science Lessons for 7th Grade and 8th Grade, KS3 and Checkpoint Science in preparation for GCSE and IGCSE Science.

Testing for Fats

1. Chop up each food.
2. Add ethanol to a depth of 2 cm.
3. Shake the food and ethanol gently.
4. Pour some cold water into a second test tube to a depth of 5 cm.
5. Pour a little of the ethanol that has been mixed with the food into the test tube of cold water.
6. If fat is present in the food, a white cloudy layer will from in the cold water.

Testing for Protein

1. Chop up each food.
2. Add a a small quantity of food sample to a teat tube and add an equal quantity of sodium hydroxide solution.
3. Shake the tube gently.
4. Add a drop of copper sulfate solution.
5. Look for a purple colour. This indicates the presence of protein.
6. If a purple colour is not seen, repeat steps 4 and 5. If the purple colour does not appear after a few drops of copper sulfate solution have been added, stop the test and record protein as absent.

This is also called the Biuret Test for protein. The Biuret solution contains sodium hydroxide and copper sulfate.

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