food tests for biological molecules - big to small

Question 1

what is the test for starch?

Answer 1

iodine solution

Question 2

explain the test for starch

Answer 2

1. place food sample on a spotting tile
2. add a few drops of iodine solution to the sample
3. blue- black colour indicates starch

Question 3

what is the test for glucose / reducing sugars?

Answer 3

benedicts solution

Question 4

explain the test for glucose / reducing sugars?

Answer 4

1. place food sample in a boiling tube
2. add benedict’s solution to the sample of food in solution
3. place in a water bath at 80•c for 5 minutes
4. a change from blue to brick red if present
   (if green, yellow or orange means less sugar present)

Question 5

what is the test for protein?

Answer 5

biuret test

Question 6

explain the test for protein

Answer 6

1. place food sample in a boiling tube
2. add enough biuret solution for colour to be pale blue
3. if protein is present colour will change to mauve / purple

Question 7

what is the test for lipids?

Answer 7

ethanol test

Question 8

Explain the test for lipids?

Answer 8

1. Place food sample in a test tube
2. Add small amount of ethanol and shake to dissolve any lipid in the alcohol.
3. Add equal volume of water
4. Cloudy white colour ( emulsion will form) indication presence of lipid