food tests

• what solution do you use to test starch?

  iodine
• how do you test sugar?

  benedict's solution
• what is biuret solution used to test?


  proteins
• how do you test for lipids?

  sudan III
• what is the starting colour of iodine?


  orange
• what is the only solution that has no colour at the start?

  sudan III
• if no changes in the practical happened, all solutions stay the same colour
• what colour does the test for starch go if positive?


  blue or black
• when testing for lipids, what colour will the positive result be?


  bright red
• for testing protein, what colour is it when the result is positive?


  Purple
• what colour does testing sugar become when positive?


  bright red
• How to test for starch

  1. Gather materials: iodine solution, sample, blue glass.
  2. Add iodine solution, mix well.
  3. Observe: blue-black color = starch present, no color change = starch absent
• how to test for protein

  1. Prepare a food sample and transfer 2 cm³ to a test tube
  2. Add 2 cm³ of Biuret solution
  3. Gently shake the tube
  4. Observe color change (blue to purple)
• how to test for lipids

  1. Prepare a food sample and transfer 5 cm³ to a test tube
  2. Add 3 drops of Sudan III stain solution
  3. Gently shake the tube
  4. Observe separation into two layers (top layer bright red if lipids are present)
• how to test for sugar?

  1. Prepare a food sample and transfer 2 cm³ to a test tube
  2. Prepare a water bath at 75°C
  3. Add Benedict's solution (about 10 drops)
  4. Place the test tube in the water bath for 5 minutes
  5. Observe color change (blue to green, orange, or brick red)