Core Practical 1.13B - Food Tests

Question 1

Food Tests:

Test for Glucose:

Answer 1

• Add Benedict’s solution to the sample solution in a test tube, and put in boiling water bath for 5 mins
• If positive, color changes from blue to orange/brick red.

Question 2

Food Tests:

Test for Starch:

Answer 2

• Add drops of iodine solution to the food sample
• If positive, colour changes from orange-brown to blue-black

Question 3

Food Tests:

Test for Protein:

Answer 3

• Add drops of Biuret solution to the food sample
• If positive, colour changes from blue to violet / purple

Question 4

Food Tests:

Test for Lipids:

Answer 4

• Mix the food sample with 4cm³ of ethanol
• Filter the ethanol solution into another test tube.
• Combine the filtered solution with an equal volume of cold distilled water (4cm³).
• If positive, a cloudy emulsion forms. If negative, remains colourless

Question 5

Food Tests

Equipment:

Answer 5

• Test tubes
• Reagents (Benedict’s, iodine, Biuret, Ethanol), test substances

Question 6

Food Tests:

Variables

Answer 6

• Dependent: Presence and type of biomolecules indicated by color change or precipitate.
• Independent: Type of chemical reagent used.
• Control: Amount of substance and reagent used.