Dcpip Test For Vitamin C Igcse
Food Tests
Revision notes on the topic 'Food Tests' for CIE IGCSE 0610/0970 Biology
Describing Food Tests
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 2cm 3 of ethanol and shaken
- The ethanol is added to an equal volume of cold water
- A positive test will show a cloudy emulsion forming
The Ethanol Test for Lipids
Test for Vitamin C
- Add 1cm 3 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
Exam Tip
When describing food tests in exam answers, make sure you give the starting colour of the solution and the colour it changes to for a positive result.
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Dcpip Test For Vitamin C Igcse
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