Reducing and Non Reducing Sugars Summary

Reducing and Non-Reducing sugars
First review @September 9, 2023

Practise Q's Done

Reducing sugars are monosaccharides whereas non-reducing sugars are polysaccharides

e.g. glucose- monosaccharide

e.g. sucrose- polysaccharide (glucose+ fructose)

Monosaccharide general formula- (Ch_2O)n

Disaccharide general formula- C_12H_22O_11

this is because disaccharides are formed through condensation polymerisation,
therefore one molecule of H_2O is removed, that’s why it isn’t C12_H24O_12)

Test for reducing sugars:

Benedict’s test

place sample to be tested in a boiling tube, if not in liquid form, grind up and mix
with water

add equal volume of Benedict’s Reagent to the sample

place boiling tube in a water bath for 15 minutes and observe any colour change

(depending on the concentration of sugar in the sample) the solution will change
from blue to green to yellow to orange to brick red. if there is no colour change,
reducing sugars aren’t present

Test for non-reducing sugars:

Benedict’s test with hydrochloric acid

heat sample to be tested in a water bath with hydrochloric acid and Benedict’s
Reagent

the hydrochloric acid hydrolyses the non-reducing sugars, which causes the
glycosidic bonds to break and so Benedict’s Reagent reacts with the sample

without the hydrochloric acid, the Benedict’s Reagent will not react with the non-
reducing sugars and the solution will remain blue




Reducing and Non-Reducing sugars 1