Food Tests

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

  Grind up food samples using a 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 starch 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.