1. 23 / Thursday
Kaupapa:
Test for the presence of starch by using iodine solution
Test for the presence of glucose by using Benedict’s solution

2. HOMEWORK (due Monday)
Worksheet
Food Investigation

3. Do you remember?
Carbohydrates can be in three different forms – what are they?
What’s the difference between starch and sugar?
What was the name of the solution used for testing proteins?
What happens when proteins are present in the food?

4. Practical – Food Tests Protein Lipids Starch (carbohydrate)
Glucose (carbohydrate)

5. Food Test: Proteins
Add three drops of Biuret solution (blue) to the food.
In the presence of proteins, it turns purple. It stays blue otherwise.

7. Food Test: Lipids
Add a few drops of ethanol and shake the mixture thoroughly. Then add a few drops of distilled water.
The food turns cloudy if it contains lipids.

9. Food Test: Carbohydrates (Starch)
Add a few drops of brown iodine solution.
The food turns black or dark blue if it contains starch.

10. Food Test: Starch Food Result Presence of Starch Bread Infant formula
Potato
Weet-bix
Egg white
Lemonade

12. Food Test: Carbohydrates (Glucose)
Add a few drops of blue Benedict’s solution, then heat it over a Bunsen.
The food first turns green, then yellow, then orange/red if glucose is present.

13. Food Test: Glucose Food Result Presence of Glucose Bread
Infant formula
Lemonade
Sugar-water

15. What have we learnt today?
What is the name of the chemical used for testing starch?
What happens when starch is present?
What is the name of the chemical used for testing glucose?
What happens when glucose is present?