- Add a solution of Iodine (in potassium iodide solution) to the sample.
- If starch is present colour will change from yellow-brown to blue-black
1 of 5
Reducing Sugar Test
- Add Benedict's solution (alkaline copper sulphate) to the sample.
- Heat to 80C in a water bath.
- The solution will change from blue to an organge-red precipitate.
2 of 5
Non-reducing Sugar Test
- First if the test for a reducing sugar has came back negative (no colour change)
- Make sure there are no reducing sugars in the solution by boiling with hydrocholoric acid.
- Cool the solution and neutralise it by adding sodium hydrogencarbonate.
- Carry out the reducing sugar test again.
- If non-redcing sugars present the solution will change from blue to an organge-red precipitate
3 of 5
- Add Biuret reagent to sample.
- If proteins are present, the biuret will react with the peptide bonds found in the protein.
- The solution will change from blue to lilac.
4 of 5
- Mix the sample with ethanol to dissolve the lipid present.
- Then pour the liquid (alcohol with dissolved fat) into water contained in another clean test tube.
- If lipid is present, a cloudy white emulsion will form near the top of the water.
5 of 5