food tests

• What should you be able to describe by the end of the video on chemical tests?

  How to carry out the chemical tests for carbohydrates, proteins, and lipids
• What are the key things to learn for the chemical tests?

  • Chemicals used to test for each food group
  • Positive results for each test
• Why is it important to wear safety goggles during the chemical tests?

  Because all of the chemicals used are potentially hazardous
• What is the first step in preparing a food sample for testing?

  Grind the food sample with distilled water using a mortar and pestle
• What is done after grinding the food sample with distilled water?

  The paste is transferred to a beaker and more distilled water is added
• What is the purpose of filtering the solution after mixing?

  To remove suspended food particles
• What color does iodine solution turn if starch is present?

  Blue-black
• What are the steps to test for carbohydrates?

  1. Test for starch:

  • Add 2 cm³ of food solution to a test tube
  • Add a few drops of iodine solution
  • Observe color change (blue-black if starch is present)

  1. Test for sugars:

  • Add 2 cm³ of food solution and 10 drops of Benedict solution
  • Heat in a water bath for 5 minutes
  • Observe color change (green, yellow, or brick red indicates sugar presence)
• What does a green color indicate in the Benedict test?

  A small amount of sugar is present
• What type of sugars does the Benedict test work for?

  Reducing sugars, such as glucose
• How to test for proteins?

  1. Add 2 cm³ of food solution to a test tube
  2. Add 2 cm³ of Biuret solution
  3. Observe color change (blue to purple/lilac indicates protein presence)
• What is the procedure for testing lipids?

  1. Grind food with distilled water using a mortar and pestle
  2. Transfer 2 cm³ of food solution to a test tube
  3. Add a few drops of distilled water and ethanol
  4. Gently shake the solution
  5. Observe for a white cloudy emulsion (indicates lipids present)
• What indicates the presence of lipids in the solution?

  A white cloudy emulsion forms
• Why is it important to avoid naked flames when testing for lipids?

  Because ethanol is highly flammable
• Where can you find questions on testing for chemicals in foods?

  In the vision workbook linked in the video