food tests

Question 1

what is the test for reducing sugars?

Answer 1

add an equal volume of Benedictus solution and heat in water bath. if glucose is present it will go from blue to green, to yellow to orange to brick red precipitate

Question 2

What is the test for a non reducing sugar?

Answer 2

add an equal volume of Benedicts solution and heat in a water bath. if a non-reducing sugar is present there will be no colour change. take a fresh sample, hydrolyse by heating with acid then add sodium hydrogen carbonate to neutralise. Add Benedicts solution and heat, a positive result is brick red precipitate

Question 3

what is the test for starch?

Answer 3

add iodine, turns from blue to black

Question 4

what is the biochemical test for lipids?

Answer 4

add ethanol shake, add water shake and a white emulsion should form if a lipid is present

Question 5

what is the biochemical test for proteins?

Answer 5

add equal volume of buret to the sample, a colour change from blue to lilac indicates a positive result