2.9 Food Tests

Edexcel IGCSE Biology

what is the test for starch?

iodine test

describe the steps for the iodine test

* place food sample into wells or onto a tile
* add a few drops of iodine solution
* record any colour change

what does a postive result for starch look like?

colour change from browny orange to blue-black

what is the test for protein?

Biuret Test

describe the steps for the Biuret Test

* place food sample in a boiling tube
* add a few drops of copper sulfate solution
* add a few drops of sodium hydroxide solution
* leave for 1 minute
* record the colour

what does a positive result for protein look like?

colour change from blue to pink

what is the test for sugar/glucose?

Benedict’s Test

describe the steps for the Benedict’s test

* place food sample in a boiling tube
* add a few drops of Benedict’s solution
* place in a water bath at 60-70 degrees celsius for 5 minutes
* record the colour

what is does a positive result for sugar/glucose look like?

colour change to yellow, brick red or green

what is the test for lipids?

ethanol test

describe the steps for the ethanol test

* place food sample in a boiling tube
* add 2cm3 of ethanol to the boiling tube
* shake the test tube
* add 2cm3 of distilled water
* shake the test tube again
* record the colour/result

what does a positive result for lipids look like?

milky white emulsion forms