B3.3 Required Practical - Food Tests

Question 1

How would you prepare a food sample for a food test?

Answer 1

1) Break up a piece of food with a pestle and mortar
2) Transfer the food to a beaker and add some distilled water
3) stir the mixture to dissolve the food
4) filter the mixture to get rid of solid bits of food

Question 2

What does the Benedict’s test test for?

Answer 2

Sugars

Question 3

How would you test for sugars in foods?

Answer 3

1) prepare a food sample in a test tube and a water bath at 75 degrees C
2) Add some Benedict’s solution to the test tube
3) Place the test tube in the water bath and leave it there for 5 minutes
4) If the solution changes from blue to green/yellow/brick red it has reducing sugar

Question 4

What so the different final colours in the Benedict’s test tell you?

Answer 4

How much sugar there is in the food

Green –> yellow –> brick red

Question 5

What do you use iodine solution to test for?

Answer 5

Starch

Question 6

How do you do a food test for starch (iodine)?

Answer 6

1) put 5cm3 of the food solution in a test tube
2) Add a few drops of iodine solution and gently shake the test tube
3) The colour should change to black/blue black if there is starch

Question 7

What does the Biuret test test for?

Answer 7

Protein

Question 8

How do you test for protein?

Answer 8

1) put 2cm3 of a food sample in a test tube
2) Add 2cm3 of Biuret solution
3) The colour will d’ange from blue to pink/purple if there is protein

Question 9

What does the Sudan II test test for?

Answer 9

Lipids

Question 10

How do you test for lipids?

Answer 10

1) Prepare a sample of food solution without filtering
2) transfer 5cm3 of this to a test tube
3) Add 3 drops of Sudan III stain solution to the test tube
4) If lipids are present the mixture will separate and a bright red layer will appear on top