3.1.2.3 Reducing and Non-Reducing Sugar Tests Flashcards

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1
Q

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

A
  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
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2
Q

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
A

Non-Reducing Sugars

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3
Q

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

A

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

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4
Q

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

A

No reducing sugar is present

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5
Q

Name a disaccharide that is a non-reducing sugar

A

sucrose

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6
Q

Which two reducing sugars are released when sucrose is hydrolysed?

A

Glucose

Fructose

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7
Q

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

A

Medium concentration of reducing sugar is present

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8
Q

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

A

High concentration of reducing sugar is present

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9
Q

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

A

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

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10
Q

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
A

A Benedict’s Test for a Reducing Sugar

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11
Q

What is a reducing sugar?

A

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.

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12
Q

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

A

Very low concentraiton of reducing sugar is present

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13
Q

What does this picture show?

A

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

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14
Q

What is a Non-Reducing Sugar?

A

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

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15
Q

Which types of sugars are all reducing sugars?

A

Monosaccharides

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16
Q

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

A

Low concentraiton of reducing sugar is present

17
Q

How would you test for a Non-Reducing Sugar?

A
  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
18
Q

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

A

Hydrolysis

19
Q

Name 2 common disaccharides that are reducing sugars

A

Maltose

Lactose

20
Q

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

A

serial dilution