Food Tests

Question 1

How would you prepare a sample?

Answer 1

1. Break up food using pestle and mortar
2. Transfer food to test tube and add distilled water
3. Mix the food with water by stirring with a glass rod
4. Filter the mixture using a funnel and filter paper, collecting the the solution
5. Proceed with food tests

Question 2

How to test for sugars

Answer 2

Put food in a test tube, add Benedict’s reagent, place in water bath to boil for 5 minutes. The initial colour will be blue, but if sugars are present, the solution will turn into a brick red precipitate

Question 3

How to test for starch

Answer 3

Add the food to a test tube, and add iodine. It will initially turn yellow-brown. If starch is present, the solution will turn blue/black

Question 4

How to test for protein/amino acids

Answer 4

Add biuret (a mixature of sodium hydroxide and copper sulfate) to a test tube with food in. It will initially turn blue, but if proteins/amino acids are present, the solution will turn lilac/purple.

Question 5

How to test for fat

Answer 5

Add ethanol to the food to dissolve the fat, and then add water. It will initially turn colourless, but if fats are present, it will turn into a white emulsion.