1. 22 / Wednesday
Kaupapa:
Test for the presence of proteins by using Biuret’s solution
Test for the presence of lipids by using ethanol

2. Do you remember?
Carbohydrates can be in three different forms – what are they?
What’s the difference between starch and sugar?
Which nutrient is needed for growth and repair?
Which nutrient has the most amount o energy?

3. The main nutrients Carbohydrates (starches, sugars and fibres)
Proteins
Lipids
(Vitamins & Minerals)

4. Carbohydrates (Starch)

5. Carbohydrates (Glucose)

6. Starch
Glucose

7. Carbohydrates (Fibre)

8. Proteins – for growth and repair

9. Lipids – contains LOTS of energy

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

11. 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.

12. Food Test: Proteins Food Result Presence of Proteins Bread
Infant formula
Cow milk
Egg yolk
Egg white
Lemonade

13. Food Test: Proteins
Proteins are made of amino acids which are held together by peptide bonds. These peptide bonds make Biuret solution turn purple.

15. 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.

16. Food Test: Lipids Food Result Presence of Lipids Cooking oil Egg yolk
Egg white
Infant formula
Cow milk

18. Food Test: Lipids
When lipids are mixed with ethanol, they are broken into tiny droplets which makes the solution appear “cloudy”. This is called emulsion.

19. What have we learnt today?
What is the name of the chemical used for testing proteins?
What happens if the food has proteins?