Food Tests

Question 1

You should include 3 steps

How do we prepare a food sample?

Use terms including: Grind, Beaker, Stir, Filter,

Answer 1

1. Grind food sample with distilled water using pestle and mortar.
2. Transfer sample to beaker and add more distilled water, stirring so chemicals in food dissolve into the water.
3. Filter solution using filter paper and funnel to remove undissolved sample.

Question 2

2 steps only. Easy.

How do we test for Starch?

Answer 2

1. 2cm^3 of food solution into test tube.
2. Add few drops of Iodine (orange colour)

Question 3

What are the results when testing for Starch?

Answer 3

Positive: Blue-Black
Negative: Stays Orange

Question 4

4 steps. Slightly more complicated

How do we test for Sugars

By sugars werefer to simple sugars or reducing sugars (glucose)

P.S heating needed !

Answer 4

1. 2cm^3 of food solution to test tube.
2. Add 10 drops of Benedicts Solution (blue colour)
3. Place test tube into beaker with hot water (from kettle)
4. Leave for 5 min

Question 5

Weird. Theres 3 by the way.

What are the results of a sugar test?

Answer 5

Green - Small amount
Yellow - Medium amount
Brick red - Large amount

Question 6

2 steps. Simple

How do we test for proteins?

Answer 6

1. 2cm^3 of food solution transferred to test tube.
2. Add 2cm^3 of Biuret Solution (Blue)

Question 7

What are the results of testing for proteins

Answer 7

Positive: Blue to Purple Lilac
Negative: Stay blue

Question 8

3 steps. Preparation is a bit different though.

How do we test for lipids?

Answer 8

During preparation do not ffilter solution as lipid molecules can stick to filter paper

1. 2cm^3 of food solution transferred to test tube.
2. Add few drops of distilled water and ethanol.
3. Gently shake.

Question 9

What are the results when testing for lipids?

Answer 9

Positive: White cloudy emulsion
Negative: Nothing happens

Question 10

What is one hazard when testing for lipids and how can this be negated?

Answer 10

Ethanol is flammable.
No naked flames should be near experiment.

Question 11

What is the test for lipids using Sudan 3?

Answer 11

2cm^3 of food sample transferred to test tube
Add 3 drops of Sudan stain solution
Shake

Question 12

What are the results when testing for lipids using Sudan 3?

Answer 12

Positive: Red layer at top
Negative: Orange colour