Food tests

• What is the aim of food tests?

  Conduct qualitative chemical tests for nutrients
• What are the four nutrients tested in food tests?

  • Starch
  • Reducing sugars
  • Proteins
  • Lipids
• What equipment is needed for the iodine test for starch?

  Food sample, test tube, iodine solution
• What is the first step in the iodine test for starch?

  Put food sample into a test tube
• What indicates the presence of starch in the iodine test?

  The solution turns from brown to blue-black
• What equipment is required for the Benedict's test for reducing sugars?

  Food sample, test tube, Benedict's solution
• What should you do after adding Benedict's solution to the food sample?

  Place in a hot water bath for a few minutes
• What color change indicates the presence of reducing sugars in the Benedict's test?

  A brick red precipitate is formed
• What equipment is needed to test for proteins?

  Test tube, measuring cylinder, Biuret solution
• What is the first step in the protein test using Biuret's reagent?

  Add Biuret's reagent to the food sample
• What indicates the presence of protein in the Biuret test?

  The solution turns from blue to purple
• What equipment is required for the lipid test?

  Food sample, test tube, ethanol, distilled water
• What is the first step in the lipid test?

  Add ethanol to the food sample
• What indicates the presence of lipids in the emulsion test?

  A white emulsion forms on the surface
• What are the sources of error in food tests?

  • Subtle color changes in tests
  • Low concentration of tested molecules
• What safety precautions should be taken during food tests?

  • Tie hair back and wear goggles
  • Handle Biuret solution with care
  • Keep ethanol away from flames
• What should be done if Biuret solution contacts skin?

  Wash immediately with water
• Why should ethanol be kept away from flames?

  Because ethanol is highly flammable