Required Practical: food tests

Question 1

What is the test for Sugars called?

Answer 1

Benedict’s Test

Question 2

What is the test for proteins called?

Answer 2

Biuret Test

Question 3

What is the test for Starch called?

Answer 3

Iodine Test

Question 4

What is the test for Lipids?

Answer 4

Sudan III test/ Emulsion Test

Question 5

How to prepare food sample:

Answer 5

1. crush food - to increase surface area
2. put in a beaker
3. stir with stirring rod until some has dissolved
4. filter with filter paper in a funnel
5. remaining solution contains all nutrients and molecules we need

Question 6

The benedict’s test ONLY tests for:

Answer 6

reducing sugars

Question 7

How to carry out the benedict’s solution?

Answer 7

1. measure out 5cm3 of your solution
2. add 10 drops of Benedict’s solution
3. place in 75 degrees water bath - 5 mins
4. observe colour change

Question 8

COLOUR CHANGE for BENEDICT’s TEST for Sugars

Answer 8

blue = no sugar present
green = low concentration
yellow = medium
brick red = high concentration

traffic lights

Question 9

How to carry out Iodine Test:

Answer 9

1. take 5cm3 of our solution
2. add a few drops of iodine
3. if sugars are present, then the solution will turn from brown to blue-black (shake test tube to make reaction happen)

Question 10

Biuret test for Proteins:

Answer 10

1. take 2cm3 of the solution
2. add biuret solution 2cm3
3. give the test tube a shake
4. should turn from blue to pink-purple if protein is present

Question 11

Sudan III test for lipids:

Answer 11

1. use UNFILTERED solution 5cm2
2. add Sudan III stain solution
3. shake test tube
4. if a lipid is present, the molecules will become stained and form a layer at the top of the solution, observable as a red line

Question 12

Emulsion test for Lipids

Answer 12

1. take your sample and add 2cm3 of ethanol, and shake vigorously
2. add distilled water to this 2cm3
3. if it goes a cloudy white colour, then a lipid is present