Food Tests

Question 1

testing for fats

Answer 1

the emulsion test

Question 1

The emulsion test (procedure)

Answer 1

add ethanol to the sample and shake, transfer the solution and add water if a lipid is present then a milky white layer will form

Question 2

testing for protein

Answer 2

the biuret test

Question 3

Biuret test (procedure)

Answer 3

add the sample to biuret solution, shake and then leave for 5 minutes, if a protein is present the solution will change from a blue to lilac

Question 4

testing for reducing sugars

Answer 4

benedicts test

Question 5

benedicts test (procedure)

Answer 5

add benedics solution to the sample and place in a water bath for around 5 minutes, if there is a reducing sugar then the solution will turn from blue to yellow-brick red dependent on the concentration of the sugar

Question 6

testing for non reducing sugars

Answer 6

benedicts test, hydrolyse the solution and repeat the benedicts test

Question 7

testing for reducing sugars (procedure)

Answer 7

use the benedicts test to ensure that the sugar is non-reducing, the colour should not change to begin with, add hydrochloric acid to hydrolyse the solution and put into a water bath, after 5 minutes neuralise with sodium bicarbonate and then repeat the benedicts test, if a reducing sugar is present then the colour should change from blue to red/orange

Question 8

testing for starch

Answer 8

potassium iodide test

Question 9

potassium iodide test (procedure)

Answer 9

add potassium iodide to the sample and if a starch is present then the solution will change from orange to blue-black