Test for glucose (a reducing sugar)

• Add?Benedict's solution?into sample solution in test tube
• Heat?at 60 - 70 °c in water bath for?5 minutes
• Take test tube out of water bath and observe the colour
• A positive test will show a colour change from?blue to orange or brick red

The Benedict's test for glucose

?Test for starch using iodine

• We can use iodine to test for the presence or absence of starch in a food sample.

The iodine test for starch

• Add drops of?iodine solution?to the food sample
• A positive test will show a colour change from?orange-brown to blue-black

Testing a potato to prove the presence of starch

Test for protein

• Add drops of?Biuret solution?to the food sample
• A positive test will show a colour change from?blue to violet / purple

The Biuret test for protein

Test for lipids

• Food sample is mixed with?2cm³?of ethanol?and shaken
• The ethanol is added to an equal volume of?cold water
• A positive test will show a?cloudy emulsion?formingThe ethanol test for lipids

Test for vitamin C

• Add?1cm³?of DCPIP solution?to a test tube
• Add a small amount of food sample (as a solution)
• A positive test will show the?blue colour of the dye disappearing

The DCPIP test for vitamin C