FOOD TESTS

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

  Grind up food samples using pestle and mortar
• Why do you mix the ground food sample with water?

  To create a solution for testing
• What equipment is used to filter the food sample?

  Funnel and filter paper
• What is the procedure to test for starch in a sample?

  Add iodine solution to sample
• What color change indicates the presence of starch?

  Brown to blue-black
• What reagent is used to test for reducing sugars?

  Benedict’s reagent
• What is the next step after adding Benedict’s reagent to the sample?

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

  A green, yellow, orange or brick red precipitate forms
• What is the procedure to test for lipids in a sample?

  Add ethanol to the sample
• What happens after adding water to the ethanol and shaking the test tube?

  A white emulsion forms if lipid is present
• What reagent is used to test for proteins in a sample?

  Biuret reagent
• What color change indicates the presence of protein?

  Blue to purple
• 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 sample
  2. Observe color change from brown to blue-black
• What are the steps to test for sugars in a sample?

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

  1. Add ethanol to the sample
  2. Add water to sample
  3. Shake test tube and observe for white emulsion
• What are the steps to test for proteins in a sample?

  1. Add Biuret reagent (potassium hydroxide and copper (II) sulphate)
  2. Shake mixture and observe for color change from blue to purple