Biology Required Practical: Food Tests

Includes;

- The Method (In Blue)

- Safety Notes (In Pink)

  • Created by: Hannah
  • Created on: 20-03-19 10:40
View mindmap
  • Biology Required Practical: Food Tests
    • Safety goggles should be worn when carrying out the tests.
      • Ensure that there is no eating or drinking during testing.
        • Biuret solution contains copper Sulphate, which is poisonous, and Sodium Hydroxide, which is caustic.
    • Method 1: Testing for Sugars
      • 1. Use a pestle and mortar to grind up a small sample of food.
        • 2. Transfer the ground up food into a small beaker. Then add distilled water. Stir the mixture so that some of the food dissolves in the water.
          • 3.Filter using a funnel with filter paper to obtain as clear a solution as possible. The solution should be collected in a conical flask.
            • 4. Half fill a test tube with some of this solution. Add 10 drops of Benedict’s solution to the solution in the test tube.
              • 5. Put hot water from a kettle in a beaker. The water should not be boiling. Put the test tube in the beaker for about five minutes.
                • 6. Note any colour change. If a reducing sugar (i.e. glucose) is present, the solution will turn green, yellow, or brick-red.  The colour depends on the sugar concentration
                  • 7. Take 5 ml of the solution from the conical flask and put it into a clean test tube.
                    • 8. Add a few drops of iodine solution and note any colour change. If starch is present, you should see a black or blue-black colour appear.
    • Method 2: Testing for Lipids
      • 1. Use a pestle and mortar to grind up a small sample of food.
        • 2. Transfer the ground up food into a small beaker. Then add distilled water. Stir the mixture so that some of the food dissolves in the water. Do not filter.
          • 3. Half fill a test tube with some of this solution.
            • 4. Add 3 drops of Sudan III stain to the solution in the test tube. Shake gently to mix. If fat is present: a red-stained oil layer will separate out and float on the water surface.
    • Method 3: Testing for Proteins
      • 1. Use a pestle and mortar to grind up a small sample of food.
        • 2. Transfer the ground up food into a small beaker. Then add distilled water. Stir the mixture so that some of the food dissolves in the water.
          • 3. Filter using a funnel with filter paper to obtain as clear a solution as possible. The solution should be collected in a conical flask.
            • 4. Put 2cm cubed of this solution into a test tube. Add 2cm cubed of Biuret solution to the solution in the test tube.  Shake gently to mix.
              • 5. Note any colour change. Proteins will turn the solution pink or purple.

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Required Practicals resources »