1. CONDUCT A QUALITATIVE TEST FOR:
Starch,
Fat,
A Reducing Sugar,
A Protein,
Vitamin C

2. Materials/Equipment Starch solution (1%) Iodine solution
Glucose solution (1%)
Benedict’s reagent (qualitative)
Protein solution e.g. albumen (1%) or milk
Sodium hydroxide solution (10%),
Copper sulphate solution (1%) (or biuret reagent)
Vegetable oil
6 Boiling tubes
Beaker (250 cm3)
Pipettes/droppers
Thermometer
Hot water bath (80 °C – 100 °C)
Test-tube holder
3 Test-tube racks
Disposable gloves
Brown paper
Scissors
Labels
Timer

3. Experiment List Go to Test for … Starch Fat A Reducing Sugar A Protein
Vitamin C

4. (i) Test for starch

5. Procedure 1. Familiarise yourself with all procedures before starting.
2. Label boiling tube A ‘starch solution’ and boiling tube B ‘water’.
3. Place 2 cm3 of the starch solution into tube A.
4. Place 2 cm3 of water into tube B. This acts as the control.

6. Procedure 5. Add 2–3 drops of iodine solution to each tube.
6. Swirl each tube.
7. Record result.

7. Result Sample Initial colour Final colour A – Starch solution
B – Water

8. Conclusion/Comment

9. (ii) Test for fat

10. Procedure 1. Familiarise yourself with all procedures before starting.
2. Cut two pieces of brown paper of similar size.
3. Place 2–3 drops of oil on one piece of paper and label it ‘oil’.
4. Place 2–3 drops of water on the other piece of paper and label it ‘water’. This acts as the control.

11. Procedure 5. Leave both aside to dry.
6. Hold both pieces of paper up to the light.
7. Record result.

12. Result
Sample
Translucent spot
Before drying
After drying
Oil
Water

13. Conclusion/Comment

14. (iii) Test for a reducing sugar

15. Procedure 1. Familiarise yourself with all procedures before starting.
2. Label boiling tube A ‘glucose solution’ and boiling tube B ‘water’.
3. Place 2 cm3 of the glucose solution into tube A.
4. Place 2 cm3 of water into tube B. This acts as the control.

16. Procedure 5. Add 2 cm3 of Benedict’s reagent to each tube.
6. Swirl each tube.
7. Place both tubes in the hot water bath and heat for 5 minutes.
8. Using the test-tube holder, carefully remove both tubes from the water bath and place in the test-tube rack.
9. Record result.

17. Result Sample Initial colour Final colour A - Glucose solution
B - Water

18. Conclusion/Comment

19. (iv) Test for a protein

20. Procedure 1. Familiarise yourself with all procedures before starting.
2. Label boiling tube A ‘protein solution’ and boiling tube B ‘water’.
3. Place 2 cm3 of the protein solution into tube A.
4. Place 2 cm3 of water into tube B. This acts as the control.

21. Procedure
5. Add 2 cm3 of sodium hydroxide solution to each tube followed by 2–3 drops of copper sulfate
solution (or add 2 cm3 of biuret reagent to each tube).
6. Swirl both tubes.
7. Record result.

22. Result Sample Initial colour Final colour A - Protein solution
B - Water

23. Conclusion/Comment

24. (v) Test for Vitamin C

25. Procedure Add 2cm depth of DCPIP solution to a test tube
Drip the food solution into the tube
Look for a colour change from blue to pink and then colourless
Repeat with water (control) and compare results

26. Result
Sample
Initial colour
Final colour
A – Fruit juice
B - Water

27. Conclusion/Comment

28. Food Tests – Summary Chart
Test for
Materials
Method
Positive Results
Starch
Iodine Solution
Add iodine to the food sample
A blue/black colour
Reducing sugar (Glucose)
Fehling’s solutions I and II
Add to sample and warm gently
A brick red colour
Protein
Copper sulphate (CuSO4) and sodium hydroxide (NaOH)
Add some NaOH to the moist food. Then gently pour CuSO4 solution down the side of the tube
A violet colour
Fat
Brown Paper
Rub the food onto the paper, warm gently to dry and hold the paper up to the light
A translucent spot
Vitamin C
DCPIP
Add to moist food or fruit juice
A change from blue to pink or colourless

29. END