Required practicals for all topics

Question 1

For the food tests practical of B2, how do you prepare a food sample?

Answer 1

• Get a piece of food and break it up using a pestle and mortar.
• Transfer the ground up food to a beaker and add distilled water.
• Stir the mixture with a glass rod to dissolve some of the food.
• Filter the solution using a a funnel lined with filter paper to get rid of the solid bits of food.

Question 2

For the food tests practical of B2, what solution do you use to test for Sugars?

Answer 2

• Use the Benedict’s solution to test for Sugars.

Question 3

For the food tests practical of B2, explain how you could use a test solution to test for reducing sugars in a substance.

Answer 3

• Prepare a food sample and transfer 5 cm^3 to a test tube.
• Prepare a water bath so that it’s set to 75°C .
• Add 10 drops of benedicts solution to the test tube using a pipette.
• Place the test tube in the water bath using a test tube holder and leave it in there for 5 minutes. Make sure the tube is pointing away from you.
• If the food sample contains a reducing sugar, the solution in the test tube will become green, yellow or red depending on the concentration.

Question 4

For the food tests practical of B2, what solution can you use to test for Starch?

Answer 4

• Iodine solution.

Question 5

For the food tests practical of B2, explain how you could test if Starch is present in a food.

Answer 5

• Make a food sample and transfer 5 cm^3 of your sample to a test tube.
• Add a few drops of iodine solution and gently shake the tube to mix the contents. If the sample contains starch, the colour of the solution will become blue-black.

Question 6

For the food tests practical of B2, what solution can you used to test for Proteins?

Answer 6

• The Biuret test.

Question 7

For the food tests practical of B2, explain how you can use a test solution to test for proteins.

Answer 7

• Prepare a sample of your food and transfer 2 cm^3 of your sample to a test tube.
• Add 2 cm^3 of biuret solution to the sample and mix the contents by gently shaking.
• If the sample contains protein the solution with become purple.

Question 8

For the food tests practical of B2, what solution can we use to test for lipids?

Answer 8

• The Sudan III test.

Question 9

For the food tests practical of B2, explain how we can use a solution to test for lipids.

Answer 9

• Prepare a sample of the food you’re testing (it can be unfiltered) and add 5 cm^3 of it to a test tube.
• Use a pipette to add 3 drops of Sudan III solution to the test tube and gently shake.
• Sudan III solution stains lipids. If the sample contains lipids, the mixture will separate out into two layers. The top layer will be bright red. If no lipids are present, no separate red layer will form.