SB1f - Testing foods

Question 1

What test do we use when we are testing for starch and state the colour change.

Answer 1

Iodine test - use iodine solution - from yellow - black

Question 2

What test do we use when we are testing for sugars/carbohydrates and state the colour change.

Answer 2

benedicts solution + heat it

From blue -> green -> orange -> red
increasing in concentration

Question 2

What test do we use when we are lipids/fats for starch and state the colour change.

Answer 2

emulsion test - use ethanol - colorless to cloudy white

Question 2

What test do we use when we are testing for Proteins and state the colour change.

Answer 2

Biuret - Turns from blue to purple

Question 3

State what is meant by a Qualitative?

Answer 3

Qualitative tests show whether a substance is present or not but not the amount

Question 4

State what is meant by a Quantitative?

Answer 4

Quantitative tests give the amount of substance that is present

Question 5

What are the risks of Food tests?

Answer 5

Risks
* Potassium hydroxide can be harmful to skin and eyes.
* Hot water can burn skin

Question 5

What safety measures should be taken?

Answer 5

Safety measures
* Wear eye protection.
* Do not taste any of the foods.
* Take care with hot water.
* Wash off any splashes immediately.

Question 6

What is a colorimeter?

Answer 6

• A calorimeter is a machine used in the process of calorimetry. Small samples of
  material are placed in the machine which burns them. The energy given off
  when the material burns is measured.

Question 6

State the steps needed to measure the energy in food?

Answer 6

Steps:

1.Take a fixed mass of your chosen food (e.g. 10g)
2.Put in on a mounted needle
3.Burn it under a test tube with a fixed volume of water (e.g. 20cm3)
4.Record the temperature of the water
5.Repeat
6.Calculate energy given using the formula