Required Practical 4 - Food Tests

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

• Grind up food samples using pestle and mortar

• Mix with water

• Filter with funnel and filter paper

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

• Add iodine solution to sample.

If starch is present, solution turns from brown to blue-black

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

• 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

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

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

• Shake mixture.

If protein is present, solution turns from blue to purple

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

• Add ethanol to the sample.

• Add water to sample.

• Shake test tube.

White emulsion formed if lipid present