food tests

Question 1

how to test for starch

Answer 1

-add iodine to the sample
-if the solution turns blue/black starch is present

Question 2

how to test for lipids

Answer 2

-add ethanol to sample
-shake test tube
-add water
-if lipids are present a white emulsion appears

Question 3

how to test for reducing sugars

Answer 3

-benedicts test
-add benedicts reagent to the sample
-heat solution gently
-a brick red precipitate if reducing sugars are present

Question 4

how to test for non-reducing sugars

Answer 4

-do the benedicts test
-add HCl to the sample and heat gently
-neutralise solution with sodium hydrogen carbonate solution
-add benedicts solution to reagent
-brick red precipitate means positive

Question 5

how to test for proteins

Answer 5

-biurets test
-add sodium hydroxide solution to sample
-add copper sulphate solution
-positive= purple
if not it will remain blue