Biochemical tests using Benedict’s reagent for reducing sugars and non-reducing sugars. Iodine/potassium iodide solution for starch.

Add Benedicts solution to the sample and heat:

• If it turns orange it is a reducing sugar
• If its blue then do the following:

Add hydrochloric acid and heat for a further 5 minutes, after this add hydrogen carbonate to neutralise it. Now repeat the process from the begining of the test and add benedicts solution and then heat:

• If it turns orange then it is a non-reducing sugar
• If it stays blue then it is not a sugar at all.

Acid is added to hydrolyse the non-reducing sugars breaking them down into monomers- reducing sugars.
The solution is neutralised as acid would prevent the Benedicts test from working.

----------------------------

To test for starch pipette a couple of drops of iodine on to the sample you are testing.

• If it stays red then there is no starch
• If it goes blue/black then there is starch.