Lesson 1: Food Tests (Reducing Sugars)

Carbohydrates

Testing for reducing sugars

1. Label some test tubes for the substances to be tested
2. Add 2cm² of test solution to labelled test tubes
3. Add 10 drops of Benedict’s reagent (this is around 0.5cm³) to each test solution, without the dropper pipette touching the inside of the test tube
4. Half fill a 400cm³ beaker with boiling water
5. Use the test tube holder to transfer the test tube into the hot water. Observe the colour changes in the test tube over 2 minutes
6. Return the test tube to the test tube rack. Make a note of your observations
7. Repeat the test for all your samples

If there is a reducing sugar present, there should be a colour change. Benedict’s reagent is blue and will change to a green, yellow, orange, brown or brick-red suspension.

However, a green solution indicates that there is a low concentration of reducing sugars.