Food Tests

Question 1

Starch

Answer 1

Add dilute iodine solution and mix well, colour change from yellow/brown to blue/black

Question 2

Glucose (reducing sugars)

Answer 2

Add Benedict’s reagent, mix well and boil for one minute, colour change form blue to brick red ppt

Question 3

Sucrose (non-reducing sugars)

Answer 3

Add 1cm^3 of HCL to the sample and boil to hydrolyse (break down) the sucrose (into glucose/fructose (reducing sugars)), neutralise with an alkali then boil for one minutes with Benedict’s solution, colour change from blue to brick red

Question 4

Lipid

Answer 4

Mix the sample with ethanol to dissolve any lipids present, shake with an equal volume of distilled water, the dissolved lipids are insoluble in water so they come out of the solution and form an emulsion, colour change from colourless to cloudy white emulsion

Question 5

Protein

Answer 5

Add Biuret Reagent and mix well, colour change from blue to purple if protein is present