Food tests

Question 1

How to make food solution

Answer 1

Grind food sample into paste using mortar and pestle
Transfer paste into beaker and add more water. Stir so the chemicals dissolve into the water.
Filter the solution to remove suspended food particles

Question 2

Method - testing for carbohydrates

Answer 2

Place 2cm^3 of food solution into a test tube.
Add a few drops of iodine solution.
If starch is present, the iodine solution will turn blue / black. If not, it will stay orange.

Question 3

Method - testing for sugars

Answer 3

Place 2cm^3 of food solution into a test tube
Add 10 drops of benedict’s solution (blue)
Place test tube in beaker. Half fill with hot water. Leave for 5m
If sugars are present, benedict’s solution will change colour.

Green = small amount
Yellow = medium amount
Red = large amount

*only works for reducing suagrs, such as glucose

Question 4

Method - testing for proteins

Answer 4

Place 2cm^3 of food solution in test tube.
Add 2cm^3 of biuret solution.
If protein is present, the biuret solution will turn a blue colour.

Question 5

Method - testing for lipids / fats

Answer 5

Grind food using distilled water with mortar and pestle. (dont filter)
Transfer 2cm^3 food solution to test tube.
Add a few drops of distilled water and ethanol
If lipids are present, a white cloudy emulsion forms.