2.2 Food Tests

Question 1

What are the two types of sugar?

Answer 1

Reducing and non reducing

Question 2

What is the process of the test for reducing sugars?

Answer 2

• Add Benedicts reagent

- heat in water bath that has been brought to boil

Question 3

What colour is Benedicts reagent?

Answer 3

Blue

Question 4

If the test is positive what will happen?

Answer 4

A coloured precipitate will form

Question 5

What is the colour change of the precipitate?

Answer 5

Blue > green > yellow > orange > brick red

Question 6

What happens the higher the concentration of the precipitate?

Answer 6

The further the colour change

Question 7

What does the colour change indicate?

Answer 7

The presence of a reducing sugar

Question 8

How can you compare the amount of reducing sugar in different solutions?

Answer 8

Compare the colour changes in both

Question 9

What is a more accurate way of comparing the amount of reducing sugar in solutions?

Answer 9

Weighing the precipitate

Question 10

If the test for reducing sugars is negative what could there still be?

Answer 10

A non reducing sugar present

Question 11

What do you have to do to test for non reducing sugars?

Answer 11

Break them down to monosaccharides

Question 12

How do you break them down to monosaccharides?

Answer 12

By getting a new sample of solution
Adding dilute hydrochloric acid
Heat in water bath

Question 13

What do you neutralise the solution with?

Answer 13

Sodium hydrogen carbonate

Question 14

What is the test for sugars?

Answer 14

Benedicts test

Question 15

What do you do after neutralising in the test for non reducing sugars?

Answer 15

Carry out the Benedicts test again

Question 16

If the test is positive why will happen?

Answer 16

A colours precipitate will form

Question 17

If the test is negative what will happen?

Answer 17

The solution will stay blue meaning it doesn’t contain any sugar

Question 18

What do you use to test for glucose?

Answer 18

Test strips dipped in reagent

Question 19

What happens to the colour strips?

Answer 19

They change colour of glucose is present

Question 20

What is the test for starch?

Answer 20

Iodine test

Question 21

What does the iodine test involve?

Answer 21

Adding dissolved potassium iodide solution to the test sample

Question 22

If starch is present what happens to the sample?

Answer 22

It changes from browny orange to blue black

Question 23

What does the biruet test test for?

Answer 23

Proteins

Question 24

What is the first stage of the biuret test?

Answer 24

Add a few drops of sodium hydroxide to make the solution alkaline

Question 25

What is the second stage of the biuret test?

Answer 25

Add some copper sulfate solution

Question 26

If a protein is present what will happen?

Answer 26

Solution turns purple

Question 27

What does emulsion test test for?

Answer 27

Lipids

Question 28

What do you do in the emulsion test?

Answer 28

Shake the test substance with ethanol for a minute then pour the solution in water

Question 29

If a lipid is present-

Answer 29

Solution turns milky