tests

• What safety precautions should be taken when performing these tests?

  Wear safety goggles and clean up spills with plenty of water
• What is the first step in preparing food for testing?

  Grind the food with a small amount of distilled water in a mortar and pestle
• Why do we need to filter the food mixture after grinding?

  To remove solid food particles that could interfere with test results
• How do you test for starch in a food solution?

  Add iodine and potassium iodide solution, which turns blue-black in the presence of starch
• What color indicates the presence of starch when using iodine solution?

  Blue-black
• What is the procedure for testing proteins in a food solution?

  Add dilute sodium hydroxide and dilute copper II sulfate, which turns purple if protein is present
• What does the biuret solution detect?

  Peptide bonds
• Why would a solution of amino acids give a negative result in the protein test?

  Because it does not contain peptide bonds
• What is the key point about the test for lipids?

  The food mixture must not be filtered
• How do you test for lipids in a food solution?

  Add ethanol and water, then shake the solution; a white cloudy emulsion indicates lipids are present
• What indicates the presence of lipids in the lipid test?

  A white cloudy emulsion forms
• What safety precaution must be taken when testing for lipids?

  Do not carry out the experiment near any flames due to the flammability of ethanol
• What are the tests for the presence of biological molecules

  • Starch test: Iodine solution turns blue-black
  • Protein test: Biuret solution turns purple
  • Lipid test: White cloudy emulsion forms with ethanol and water
• What is the general procedure for testing food for biological molecules?

  1. Grind food with distilled water
  2. Filter to remove solid particles
  3. Conduct specific tests for starch, protein, and lipids
  4. Observe color changes or formations for results