RP 4 - Food tests

• What is the first step in preparing a food sample for testing?

  Grind up food samples using pestle and mortar
• Why is water mixed with the ground food sample during preparation?

  To create a solution that can be filtered
• What is the purpose of filtering the food sample?

  To separate solid particles from the liquid
• What reagent is used to test for the presence of starch in a sample?

  Iodine solution
• What color change indicates the presence of starch when iodine solution is added?

  The solution turns from brown to blue-black
• What is the first step in testing for reducing sugars in a sample?

  Add Benedict’s reagent to the sample
• What is the next step after adding Benedict’s reagent to test for reducing sugars?


  Boil the test tube in a hot water bath
• What indicates the presence of reducing sugars after boiling?

  A brick red precipitate forms
• What reagent is used to test for the presence of protein in a sample?

  Biuret reagent (potassium hydroxide and copper (II) sulphate)
• What happens to the solution if protein is present after adding Biuret reagent?

  The solution turns from blue to purple
• What is the first step in testing for lipids in a sample?

  Add ethanol to the sample
• What is the next step after adding ethanol to test for lipids?

  Add water to the sample
• What indicates the presence of lipids after shaking the test tube?

  A white emulsion is formed
• What are the steps to prepare a food sample for testing?

  1. Grind up food samples using pestle and mortar
  2. Mix with water
  3. Filter with funnel and filter paper
• What are the steps to test for starch in a sample?

  1. Add iodine solution to the sample
  2. Observe color change: brown to blue-black indicates starch presence
• What are the steps to test for reducing sugars in a sample?

  1. Add Benedict’s reagent to the sample
  2. Boil the test tube in a hot water bath
  3. Observe: brick red precipitate indicates reducing sugars
• What are the steps to test for protein in a sample?

  1. Add Biuret reagent (potassium hydroxide and copper (II) sulphate)
  2. Shake the mixture
  3. Observe: blue to purple indicates protein presence
• What are the steps to test for lipids in a sample?

  1. Add ethanol to the sample
  2. Add water to the sample
  3. Shake the test tube
  4. Observe: white emulsion indicates lipid presence