In this module, you will learn:
- food test for proteins
- food test for glucose
- food test for starch
- food test for fats
Resources to help you:
- Textbook: page 56, 57 and 58
- Notebook: page 16
Test for protein of albumen (egg white)
Test for proteins
Biuret solution is used to test for proteins. A few drops of the Biuret solution is added to the food sample to be tested.
Make sure to shake the solution after each drop.
If a purple colour is observed, then protein is present in the food sample.
Test used: Biuret Test
Observation: The solution produce a purple solution
Test for glucose
To test for glucose, we use Benedict’s solution.
Prepare the food sample to be tested in a solution form. An equal (same) amount of Benedict’s solution is added to the food sample.
The mixture is then put into a beaker containing hot water.
A colour change to orange or red precipitate means glucose is present in the food sample.
Test used: Benedict’s solution
Observation: The colour changed to an orange or red precipitate.
Tests for glucose
Testing for presence of starch in leaves
Note on this video:
The video describe how to test for starch in leaves. If iodine is added to fresh leaves, it will not produce any result. Therefore, the leaves need to be treated before doing the iodine test. Refer to page 13 of your Notebook for more information.
Test for starch
To test for starch, we use iodine solution. Iodine solution is a clear brown solution.
By adding a few drops to the food sample, if there is a colour change from brown to blue-black, starch is present.
Test used: Iodine solution
Observation: The colour of iodine turns to a blue-black colour.
Test for fats
To test for fats, we use a grease spot test. The food sample is added to a piece of filter paper. Most types of paper will work too.
The paper is then left to dry. Food that contains fat will leave a translucent spot.
Test used: Filter paper
Observation: A translucent spot is present after leaving it to dry.
Simple test for fats or lipids using paper