Practical: Food Tests

Question 1

Describe how you would prepare a sample of food to be tested

Answer 1

1. Grind up food samples using pestle and mortar.
2. Mix with water.
3. Filter with funnel and filter paper.

Question 2

Describe how you would test for the presence of starch in a sample

Answer 2

1. Add iodine solution to sample.
2. If starch is present, solution turns from brown to blue-black.

Question 3

Describe how you would test for the presence of a reducing sugar in a sample

Answer 3

1. Add Benedict’s reagent to sample.
2. Boil test tube in a hot water bath.
3. If reducing sugar is present, a brick red precipitate forms. If not, the solution remains blue.

Question 4

Describe how you would test for the presence of protein in a sample

Answer 4

1. Add Biuret reagent (potassium hydroxide and copper (II) sulphate).
2. Shake mixture.
3. If protein is present, solution turns from blue to purple.

Question 5

Describe how you would test for the presence of lipids in a sample

Answer 5

1. Add ethanol to the sample.
2. Add water to sample.
3. Shake test tube.
4. White emulsion formed if lipid present.