food tests !

Question 1

benedict’s test - reducing sugar !

Answer 1

1. place 2cm3 of food sample into test tube
2. add 2cm3 of Benedict’s solution to food sample
3. shake mixture & place test tube in a boiling water bath for 2-3 mins

Question 2

benedict’s test - results !

Answer 2

remains blue : no reducing sugar present
blue -> yellow / orange : moderate amount of reducing sugar present
blue -> brick red : large amount of reducing sugar present

Question 3

iodine test - starch !

Answer 3

add 2-3 drops of iodine solution to a small amount of food sample on a white tile

Question 4

iodine test - results !

Answer 4

remains brown : no starch present

brown -> blue black : starch present

Question 5

biuret test - protein !

Answer 5

1. add 2cm3 of Biuret solution to an equal volume of food sample
2. shake to mix & leave for 5mins

Question 6

biuret test - results !

Answer 6

remains blue : no protein present

blue -> violet : protein present

Question 7

ethanol emulsification test - fats !

Answer 7

1. add 2cm3 of ethanol to 2cm3 of food sample in test tube

2. shake & leave for 5mins

Question 8

ethanol emulsification test - results !

Answer 8

remains colourless : no fats present

white emulsification observed : fats present

Question 9

solid food samples for ethanol emulsification !

Answer 9

1. cut the solid food sample into smaller pieces & place 2cm3 of the food sample into test tube
2. add 2cm3 ethanol to sample and shake well
3. decant ethanol into another test tube containing 2cm3 of distilled water & shake