Required practical 4 - Food tests

Question 1

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

Answer 1

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

Question 2

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

Answer 2

• Add iodine solution to sample.

- 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

• Add Benedict’s reagent to sample.
• Boil test tube in a hot water bath.
• If reducing sugar, 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

• Add Biuret reagent (potassium hydroxide and copper sulfate).
• Shake mixture.
• 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

• Add ethanol to the sample.
• Add water to sample.
• Shake test tube.
• White emulsion formed if lipid is present.