Food Tests

Question 1

What is used to test for reducing sugars?

Answer 1

Benedict’s Test.

Prepare sample.
Transfer 5cm^3 to a test tube.
Prepare a water bath and set to 75 degrees celsius.
Add about 10 drops of Benedict’s solution to the test tube.
Using a test tube holder, place the test tube into the water bath (pointing away from you) and wait 5 minutes.

Blue -> Green, yellow or red (low concentration to high)

Question 2

What is used to test for starch?

Answer 2

Iodine solution.

Prepare a sample.
Transfer 5c^3 to a test tube.
Add a few drops of iodine solution and gently shake.

Blue/Black -> Orange-brown

Question 3

What is used to test for proteins?

Answer 3

Biuret test.

Prepare a sample.
Transfer 2cm^3 of the sample to a test tube.
Add 2cm^3 of biuret solution and gently shake.

Blue-> Purple

Question 4

What is used to test for lipids?

Answer 4

Sudan III test.

Prepare sample.
Transfer 5cm^3 into a test tube.
Using a pipette, add 3 drops of Sudan III solution and gently shake.

Mixture will separate into layers, the top layer being bright red.

Question 5

How do you prepare a food sample?

Answer 5

Break up the food using a mortar and pestle.
Transfer the food sample into a beaker and add distilled water.
Stir with a glass rod to dissolve some of the food.
Filter the solution with a filter funnel to remove the remaining solid pieces.