Food tests

• What is the purpose of the Benedict's test?

  To test for reducing sugars
• What does the iodine test detect?

  It detects starch
• What does the Buret test check for?

  It checks for proteins
• What is the purpose of the Sudan 3 test?

  To test for lipids
• What additional test is covered for those doing the Edexcel course?

  The emulsion test for lipids
• What is the first step in preparing a food sample for testing?

  Break it up using a mortar and pestle
• What should you do after crushing the food sample?

  Add it to a beaker with distilled water and stir
• How do you filter the food sample solution?

  Using a funnel lined with filter paper
• What does a blue solution indicate in the Benedict's test?

  No reducing sugars are present
• What color change indicates the presence of reducing sugars in the Benedict's test?

  Green, yellow, or brick red
• How do you perform the iodine test?

  Add a few drops of iodine solution to the food sample
• What color change indicates the presence of starch in the iodine test?

  From browny orange to blue black
• How much of the food sample is used in the Buret test?

  Two centimeters cubed
• What color change indicates the presence of proteins in the Buret test?

  From blue to pink or purple
• What additional reagents are needed for the Buret test in the Edexcel course?

  Potassium hydroxide followed by copper sulfate
• What is the procedure for the Sudan 3 test?

  Add three drops of Sudan 3 stain solution to the food sample
• What indicates the presence of lipids in the Sudan 3 test?

  A bright red layer at the top of the solution
• How do you perform the emulsion test for lipids?

  Add two centimeters cubed of ethanol and shake vigorously
• What indicates the presence of lipids in the emulsion test?

  A cloudy white color in the solution
• What does a clear solution indicate in the emulsion test?

  No lipids are present
• What are the steps to prepare a food sample for testing?

  1. Break the food using a mortar and pestle.
  2. Add the crushed food to a beaker with distilled water and stir.
  3. Filter the solution using a funnel lined with filter paper.
• What are the key food tests and their corresponding substances?

  • Benedict's test: Reducing sugars
  • Iodine test: Starch
  • Buret test: Proteins
  • Sudan 3 test: Lipids
  • Emulsion test (Edexcel): Lipids
• What are the safety precautions for the Benedict's test?

  • Use a test tube holder to place the test tube in the water bath.
  • Point the test tube away from yourself and others.
• How do the tests for sugars, starch, proteins, and lipids differ in their procedures?

  • Sugars: Benedict's test with heating.
  • Starch: Iodine test with color change.
  • Proteins: Buret test with color change.
  • Lipids: Sudan 3 test with staining or emulsion test.