Food Tests

Question 1

Test for glucose (a reducing sugar)

Answer 1

Add Benedict’s solution into sample solution in test tube
Heat at 60 - 70 °c in water bath for 5 minutes
Take test tube out of water bath and observe the colour
A positive test will show a colour change from blue to orange or brick red

Question 2

Test for starch using iodine

Answer 2

We can use iodine to test for the presence or absence of starch in a food sample.

Question 3

The iodine test for starch

Answer 3

Add drops of iodine solution to the food sample (potato )
A positive test will show a colour change from orange-brown to blue-black

Question 4

Test for protein

Answer 4

Add drops of Biuret solution to the food sample
A positive test will show a colour change from blue to violet / purple

Question 5

Test for lipids

Answer 5

Food sample is mixed with 2cm3 of ethanol and shaken
The ethanol is added to an equal volume of cold water
A positive test will show a cloudy emulsion forming

Question 6

Test for vitamin C

Answer 6

Add 1 cm3 of DCPIP solution to a test tube
Add a small amount of food sample (as a solution)
A positive test will show the blue colour of the dye disappearing