food tests

Question 1

what is the test for starch and what is the result?

Answer 1

add iodine

positive result = turns from orange to blue black

Question 2

what is the test for reducing sugars and what is the result?

Answer 2

add benedicts reagant and heat

positive test result: blue to green, yellow, orange or brick red

the more red the more concentration of the reducing sugar

Question 3

what is the test for non reducing sugars?

Answer 3

add acid and boil ( acid hydrolysis)
cool solution and add alkali to neutralise

add benedicts and heat

potitive result = blue to green,yellow,organge or brick red

Question 4

what is the test and result of proteins?

Answer 4

add biuret
positive result: blue to purple

Question 5

what is the test for lipids- fats and oils?

Answer 5

dissolve in ethanol and add distilled water

positive test result : white emulsion formed

Question 6

what is the colour change in starch test?

Answer 6

orange to blue black

Question 7

what is the colour change in a reducing and non reducing sugars test?

Answer 7

blue to green,yellow,orange or brick red

Question 8

what is the colour change in the test for proteins?

Answer 8

blue to purple

Question 9

what is the positive test result for lipids ?

Answer 9

white emulsion forms

Question 10

in the test for sugars why does the colour change occur at the top of the solution first ?

Answer 10

heat rises so the hottest point is at the top of the solution so particles have more kinetic energy so more successful collisions

therefore reaction happens faster