Tests

Question 1

How do we test for starch?

Answer 1

STARCH:

Add a solution of iodine to sample
If starch is present, iodine changes colour from yellow-brown to blue-black

Question 2

How can we test for reducing sugars?

Answer 2

Add Benedicts solution (alkaline copper sulphate) to sample
Heat in a water bath of 80oc
If reducing sugar is present it turns brick-red – if not present no change
Compare sample to know sugar contents in a colorimeter
If not present – do non-reducing sugar test
If present – compare on a graph to the know sugar contents solutions

Question 3

How do we test for non reducing sugars?

Answer 3

Make sure no reducing sugars in sample
Boil the sample with Hydrochloric acid
Cool solution and neutralise by adding sodium hydrogen carbonate solution
Repeat reducing sugar test again

Question 4

What is the biuret test?

Answer 4

Add biuret reagent to sample

If colour changes to lilac proteins are presen

Question 5

How can we test for lipids?

Answer 5

Mix sample with ethanol – dissolves any present lipid
Then pour liquid into water contained in another clean test tube
If lipid present – cloudy white emulsion with form near top of water