B2: FOOD TESTS

Question 1

What is the test for starch?

Answer 1

add iodine soution

Question 2

What is the result when iodine is added to a solution where starch is present?

Answer 2

colour change from orange to blue black

Question 3

What is the test for sugars?

Answer 3

add benedict’s solution

Question 4

What is the result when benedict’s solution is added to a solution where sugar is present?

Answer 4

colour change from blue to green, yellow or brick red (depeding on how much sugar is in the solution

Question 5

What is the test for proteins?

Answer 5

add biruet solution

Question 6

What is the result when biruet solution is added to a solution where protein is present?

Answer 6

colour change from blue to lilac purple

Question 7

What is the test for lipids?

Answer 7

add sudan III stain solution

Question 8

What is the result when sudan III stain solution is added to a solution where lipids are present?

Answer 8

a seperate red layer will form at the top of the liquid

Question 9

What is another way to test for lipids?

Answer 9

the emulsion test:
add ethanol

Question 10

What is the result when ethanol is added to a solution where lipids are present?

Answer 10

solution turns cloudy

Question 11

RP - Food tests: method

Answer 11

-use a pestle and mortar to grind up a small sample of food
-transfer ground food into a beaker and add distilled water
-stir the mixture so that some of the food dissolves in the water
-filter using a funnel and filter paper to obtain as clear a solution as possible (collect solution in a conical flask)
-fill a test tube halfway with the solution
-add a few drops of iodine/benedict’s/biurets/sudan III solution to the test tube based on what you are testing for (heat using water bath to test for sugars using benedict’s solution)
-note colour change