food tests

Question 1

what is the test for starch?

Answer 1

add a few drops of iodine to sample

Question 2

what is the positive result for starch?

Answer 2

orange to blue-black

Question 3

what is the test for proteins?

Answer 3

add drops of biuret solution to sample

Question 4

what is the positive result for protein?

Answer 4

blue to purple

Question 5

what is the test for lipids?

Answer 5

sample is mixed with 2cm of ethanol
shake
add equal volume of cold water

Question 6

what is the positive result for lipids?

Answer 6

cloudy white emulsion forms

Question 7

what is the test for glucose reducing sugars?

Answer 7

add benedicts solution to sample
heat in water bath at 90 degrees

Question 8

what is the positive result for glucose reducing sugars?

Answer 8

blue to green to yellow to brick-red

Question 9

what is the test for glucose non-reducing sugars?

Answer 9

add dilute hydrochloric acid
heat in a water bath
neutralise solution with alkali (sodium hydroxide)
then carry out reducing sugars test