(incomplete)
Test for Non-Reducing Sugars (Disaccharides)
-some disaccharides, like sucrose, have no effect on Benedict's reagent when heated with it.
-therefore it must be broken down into its monosaccharides first (fructose and ∝-glucose).
1) add Benedict's reagent.
2) heat in a water bath at 90°C.
3) you will not observe a colour change to brick red. The solution remains blue. Reducing sugar is not present.
4) get new sample and add dilute hydrochloric acid.
5) heat in water bath at 90°C.
6) glycosidic bonds will hydrolyse from acidity.
7) add alkali to neutralise solution (e.g. hydrogen carbonate) - test with pH paper.
8) add Benedict's reagent.
9) heat in a water bath to 90°C.
10) observe a colour change from blue to a brick red precipitate of copper oxide.
-therefore it must be broken down into its monosaccharides first (fructose and ∝-glucose).
1) add Benedict's reagent.
2) heat in a water bath at 90°C.
3) you will not observe a colour change to brick red. The solution remains blue. Reducing sugar is not present.
4) get new sample and add dilute hydrochloric acid.
5) heat in water bath at 90°C.
6) glycosidic bonds will hydrolyse from acidity.
7) add alkali to neutralise solution (e.g. hydrogen carbonate) - test with pH paper.
8) add Benedict's reagent.
9) heat in a water bath to 90°C.
10) observe a colour change from blue to a brick red precipitate of copper oxide.
Test for Starch (Polysaccharides)
1) add two drops of iodine solution to the sample (in a test tube or on a spotting tile).
2) observe a colour change to blue-black.
2) observe a colour change to blue-black.