Food Tests

Question 1

Test for starch

Answer 1

Add 3-4 drops of iodine solution (be specific if testing qualitatively) Colour change from reddish brown to blue black is positive. Faster colour change/deeper shade is more starch

Question 2

Test for reducing sugars

Answer 2

Make a solution of the substance being tested Adan equal volume of Benedictus solution. Heat in a boiling water bath colour change from blue to cloudy green to yellow to red is positive. Faster colour change and deeper shades indicates higher amounts

Question 3

Test for Protein

Answer 3

Add 5cm3 of sodium hydroxide and 5cm3 of 1%copper sulphate solution (biuret solution) to the food. Colour change of blue to purple indicates protein, the deeper the shade of purple the more protein.

Question 4

Test for fats/oils

Answer 4

Crush food in ethanol and filter
Pour this solution into a test tube containing a few cm3 of water, a white milky emulsion indicates the presence of fats/oils

Question 5

Test for Vitamin C

Answer 5

Add liquid drop by drop into 2cm3 of 0.1% DCPIP. Colour change of blue to colourless indicates presence of Vitamin C. The fewer the drops the more vitamin c present