Lesson 2: Food Tests (Non-Reducing Sugars)

Testing for non-reducing sugars

NOTE: This food test should only be carried out after a negative result for Benedict’s test for reducing sugars

1. Label the test tubes
2. Use a pasteur pipette to dispense 2cm³ of a fresh sample into a test tube
3. Use a dropper pipette to add 10 drops of dilute hydrochloric acid (HCl)to the sample
4. Half fill a 400cm³ beaker will boiling water
5. Use a test tube holder to transfer the test solution to the beaker
6. Heat for two minutes – this is the stage where acid hydrolysis may occur
7. Cool the test tube in cold water (in a beaker or under a cold tap)
8. With a spatula add sodium hydrogencarbonate to the solution until fizzing stops.
9. Add 10 drops of Benedict’s reagent (approx. 0.5cm³) to the test solution
10. Refill a 400cm³ beaker with boiling water
11. Heat the test solution for two minutes
12. Observe the colour changes in the test tubes over two minutes of heating at boiling point. Record your observations in a table

A colour change from blue to brick red, brown, orange, yellow or green indicates that a non-reducing sugar is present.