RP4 - 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 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

• Add Biuret reagent (potassium hydroxide and copper (II) sulphate)
• 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 present