3.1.2.3 Reducing and Non-Reducing Sugar Tests

Question 1

How would you carry out a Benedict’s rest for a reducing sugar

Answer 1

1. Add 2cm3 of the food sample to a test tube
2. Add an equal volume of Benedict’s Reagent
3. Heat the mixture in a boiling water bath for 5 minutes
4. Observe colour change

Question 2

What do the following instructions describe a test for?

1. Boil the sample with hydrochloric acid
2. This will hydrolyse any disaccharide into 2 monosaccharides
3. Cool solution and neutralise with sodium hydrogen carbonate
4. Add Benedict’s Reagent and heat
5. Observe colour change

Answer 2

Non-Reducing Sugars

Question 3

What do we mean when we say that the Benedict’s Test for Reducing Sugars is ‘semi-quantitative’?

Answer 3

That the colour of the result can be used to estimate the approximate amount of reducing sugar in a sample

Question 4

What does it mean if a food sample turns benedicts solution this colour?

Answer 4

No reducing sugar is present

Question 5

Name a disaccharide that is a non-reducing sugar

Answer 5

sucrose

Question 6

Which two reducing sugars are released when sucrose is hydrolysed?

Answer 6

Glucose

Fructose

Question 7

What does it mean if a food sample turns benedicts solution this colour?

Answer 7

Medium concentration of reducing sugar is present

Question 8

What does it mean if a food sample turns benedicts solution this colour?

Answer 8

High concentration of reducing sugar is present

Question 9

During a Non-Reducing sugar test why do we need to neutralise the food sample after heating it in acid?

Answer 9

Because Benedict’s reagent will not work in acidic conditions (ideally alkaline)

Question 10

What do the following instructions describe a test for?

1. Add 2cm3 of the food sample to a test tube
2. Add an equal volume of Benedict’s Reagent
3. Heat the mixture in a boiling water bath for 5 minutes
4. Observe colour change

Answer 10

A Benedict’s Test for a Reducing Sugar

Question 11

What is a reducing sugar?

Answer 11

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.

Question 12

What does it mean if a food sample turns benedicts solution this colour?

Answer 12

Very low concentraiton of reducing sugar is present

Question 13

What does this picture show?

Answer 13

The results of Benedict’s test according to the concentration of reducing sugar present

Question 14

What is a Non-Reducing Sugar?

Answer 14

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

Question 15

Which types of sugars are all reducing sugars?

Answer 15

Monosaccharides

Question 16

What does it mean if a food sample turns benedicts solution this colour?

Answer 16

Low concentraiton of reducing sugar is present

Question 17

How would you test for a Non-Reducing Sugar?

Answer 17

1. Boil the sample with hydrochloric acid
2. This will hydrolyse any disaccharide into 2 monosaccharides
3. Cool solution and neutralise with sodium hydrogen carbonate - add slowly
4. Add Benedict’s Reagent and heat
5. Observe colour change

Question 18

The process of breaking a disaccharide up into 2 monosaccharides is called…

Answer 18

Hydrolysis

Question 19

Name 2 common disaccharides that are reducing sugars

Answer 19

Maltose

Lactose

Question 20

What method would you use to produce different concentrations of sucrose from a concentrated sucrose solution?

Answer 20

serial dilution