Food Tests

Question 1

Protein

Answer 1

The biuret test- Place a protein solution in a test tube, then add at least 2cm^3 of potassium hydroxide. The mixture is then stirred and add 1% copper sulfate.

*Observation(positive result)- mauve/purple colour

Question 2

Starch

Answer 2

Iodine test- Add starch solution to a test tube then add a few drops of iodine solution.

*Observation(positive result)- blue-black colour change

Question 3

Reducing Sugar

Answer 3

Benedicts test- One ml of the analyte sample must be mixed with 2ml of benedicts reagent and heated in a bath of boiling water for 3 to 5 minutes

*Observation(positive result)- Brick red colour

Question 4

Non-Reducing Sugar

Answer 4

Benedicts Sugar- Benedict’s test- break down sample with dilute hydrochloric acid then add sodium hydroxide or bicarbonate . One millilitre of the analyte sample must be mixed with 2 millilitres of Benedict’s reagent and heated in a bath of boiling water for 3 to 5 minutes. Solids will rise to the top and will be brick red in colour if the test is positive.

Question 5

Fats

Answer 5

Grease spot: a grease spot is left behind after the fatty food is left

Emulsion test: The substance is first dissolved in ethanol. Then it is dissolved in water and shaken vigorously.

• Observation(positive result)- cloudy white precipitate