Food Tests

Question 1

How do you create a food sample?

Answer 1

1) Get a peace of the food being tested and break it up using a pestle and mortar.
2) Transfer the food (now in very small molecules) to a beaker and add some distilled water.
3) Stir the food molecules and the distilled water together with a glass rod too disolve some of the food.
4) Filter the solution using a funnel lined with filter paper to get rid of the solid bits of food.

Question 2

What does the Benedict’s Test test for?

Answer 2

Sugars

Question 3

What does the Iodine Solution Test test for?

Answer 3

Starch

Question 4

What does the Biuret Test test for?

Answer 4

Proteins

Question 5

What does the Sudan III Test test for?

Answer 5

Lipids

Question 6

How do you test for Sugars?

Answer 6

1) Prepare a food sample and transfer 5cm^3 of it too a test tube.
2) Prepare a 75°C water bath.
3) Add some Benedict’s Solution to the test tube (about 10 drops) using a pipette.
4) Place the test tube in the water bath using a test tube holder and leave it in there for 5 minutes (make sure it is pointing away from you).
5) If the food sample contains a reducing sugar, the solution in the test tube will change from the normal blue colour to green, yellow or brick red (depending in the concentration of the sugar).

Question 7

How do you test for Starch?

Answer 7

1) Make a food sample and transfer 5cm^3 of your sample too a test tube.
2) Add a few drops of Iodine Solution too the test tube and gently shake the tube to mix the contents.
3) If the sample contains starch, the colour of the solution will change from browny-orange to black or blue/black.

Question 8

How do you test for proteins?

Answer 8

1) Prepare a sample of your food and transfer 2cm^3 of the sample too a test tube.
2) Add 2cm^3 of biuret solution to the sample and mix the contents of the tube by gently shaking it.
3) If the food sample does contain protein the solution will change from blue to purple, if the food sample does not contain protein then the solution will stay blue.

Question 9

How do you test for lipids?

Answer 9

1) Prepare a sample of the food you’re testing (does not need to be filtered) and transfer 5cm^3 of it too a test tube.
2) Use a pipette to add 3 drops of Sudan III stain solution to the test tube and gently shake the tube.
3) If the mixture contains lipids, the mixture will seperate out into two layers and the top layer will be bright red. If no lipids are present, no seperate red layer will form