3.1.2.3 Reducing and Non-Reducing Sugar Tests Flashcards
How would you carry out a Benedict’s rest for a reducing sugar
- Add 2cm3 of the food sample to a test tube
- Add an equal volume of Benedict’s Reagent
- Heat the mixture in a boiling water bath for 5 minutes
- Observe colour change
What do the followign instructions describe a test for?
- Boil the sample with hydrochloric acid
- This will hydrolyse any disaccharide into 2 monosaccharides
- Cool solution and neutralise with sodium hydrogen carbonate
- Add Benedict’s Reagent and heat
- Observe colour change
Non-Reducing Sugars
What do we mean when we say that the Benedict’s Test for Reducing Sugars is ‘semi-quantitative’?
That the colour of the result can be used to estimate the approximate amount of reducing sugar in a sample
What does it mean if a food sample turns benedicts solution this colour?
No reducing sugar is present
Name a disaccharide that is a non-reducing sugar
sucrose
Which two reducing sugars are released when sucrose is hydrolysed?
Glucose
Fructose
What does it mean if a food sample turns benedicts solution this colour?
Medium concentration of reducing sugar is present
What does it mean if a food sample turns benedicts solution this colour?
High concentration of reducing sugar is present
During a Non-Reducing sugar test why do we need to neutralise the food sample after heating it in acid?
Because Benedict’s reagent will not work in acidic conditions (ideally alkaline)
What do the following instructions describe a test for?
- Add 2cm3 of the food sample to a test tube
- Add an equal volume of Benedict’s Reagent
- Heat the mixture in a boiling water bath for 5 minutes
- Observe colour change
A Benedict’s Test for a Reducing Sugar
What is a reducing sugar?
A sugar that can give an electron to the Copper (II) Sulphate found in Benedict’s reagent to make it form a red Copper (I) Oxide precipitate.
What does it mean if a food sample turns benedicts solution this colour?
Very low concentraiton of reducing sugar is present
What does this picture show?
The results of Benedict’s test according to the concentration of reducing sugar present
What is a Non-Reducing Sugar?
A sugar that is unable to give an electron to the Copper (II) Sulphate in Benedict’s Reagent so it is unable to form a red Copper (I) Oxide precipitate
Which types of sugars are all reducing sugars?
Monosaccharides
What does it mean if a food sample turns benedicts solution this colour?
Low concentraiton of reducing sugar is present
