How to test for non-reducing sugars
If a test for reducing sugars is negative, that doesn't mean there aren't any sugars present. There could be a non-reducing sugar like sucrose.
To check for this, you'll need to break down the non-reducing into monosaccharides.
You'll need to get a new sample of the food sample (test solution) and add dilute hydrochloric acid. Then carefully heat it in a water bath at around 100°C.
Then you need to neutralise it by adding sodium hydrogencarbonate.
Then carry out the Benedict's solution as normal.
A summary on how to perform this test
- Heat a new food sample with dilute hydrochloric acid.
- Add sodium hydrogencarbonate to neutralise the sample.
- Heat the sample with Benedict's reagent.
As before, if the sample changes colour to green → yellow → orange → red, then a non-reducing sugar isn't present.
If it stays blue then there's no non-reducing (or reducing) sugar present.
