Practical: Benedicts test

What to do if the sample is not already in liquid form 

It must first be ground up in water 

First step

• Add 2cm3 of the food sample being tested to 2cm3 of benedicts reagent in a test tube and filter

Second step

• Place the test tube in a gently boiling water bath for 5 minutes. 

• If the benedicts reagent does not change colour (the solution remains blue) then a reducing sugar is not present 

Third step 

• Add another 2cm3 of the food sample to 2cm3 of dilute hydrochloric acid in a test tube in a gently boiling water bath for five minutes 

• The dilute hydrochloric acid will hydrolyse any disaccharide present into its monosaccharides 

Fourth step

• Slowly add some sodium hydrogen carbonate solution to the test tube in order to neutralise the hydrochloric acid.

• Benedicts reagent will not work in acidic conditions

• Test with pH paper to check that the solution is alkaline

Fifth step

• Re test the resulting solution by heating it with 2cm3 of benedicts reagent in a gently boiling water bath for five minutes

Sixth step 

• If a non reducing sugar was present in the original sample, the benedicts reagent will now turn orange- brown 

• This is due to the reducing sugars that were produced from the hydrolysis of the non reducing sugar