RP: food tests

Question 1

What safety tip would you give and why?

Answer 1

Chemicals are hazardous so wear goggles

Question 2

Describe the method to make the food solution.

Answer 2

1. Grind the food in a pestle and mortar with a small amount of distilled water to make a paste
2. Transfer to a beaker and add more distilled water. Stir to dissolve chemicals.
3. Filter through filter paper to remove any solids.

Question 3

How much of the food solution should you use for each test?

Answer 3

2cm^3

Question 4

Describe the test for starch:

Answer 4

1. Add iodine to the food solution.
2. If the solution turns black blue, there is starch present.

Question 5

Describe the test for sugar:

Answer 5

1. Add ten drops of the blue Bennedicts solution to the food solution.
2. Place the test tube in a hot water bath for 5 minutes (to increase rate of reaction).
3. No change: no sugar, green: some sugar, yellow: more sugar, brick red: lots of sugar.

Question 6

What should you bear in mind when testing for sugar?

Answer 6

The test will only work on reducing sugars, eg. glucose, but not sucrose.

Question 7

Describe the test for protein:

Answer 7

1. Add 2cm^3 of Buirets solution to the food solution.
2. If protein is present, it will turn purple.

Question 8

Describe the test for lipids:

Answer 8

1. Add a few drops of (flammable) ethanol and shake.
2. The solution will change white and cloudy if lipids are present.

Question 9

What’s different about the food solution for lipids?

Answer 9

You shouldn’t filter it, as the lipids molecules will stick to the filter paper.