Tests Flashcards
(5 cards)
How do we test for starch?
STARCH:
Add a solution of iodine to sample
If starch is present, iodine changes colour from yellow-brown to blue-black
How can we test for reducing sugars?
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
How do we test for non reducing sugars?
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
What is the biuret test?
Add biuret reagent to sample
If colour changes to lilac proteins are presen
How can we test for lipids?
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