Food tests

  • Created by: Katy1036
  • Created on: 06-05-18 18:29

Test for Starch

1. some of the extract is placed in a test tube.

2. Iodine solution is added (2/3 drops)

3. Reddish brown   black = positive for starch

    Reddish brown    reddish brown = negative for starch

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Test for Reducing Sugars

1. put a sample of the extract in a test tube

2. add the same volume of Benedict's solution to the test tube

3. heat the test tube in a hot water bath

4. Blue   blue = negative

    Blue   green = very little reducing sugars present

    Blue   yellow =  more reducing sugars present

    Blue   orange/red = a lot of reducing sugars present

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Test for Protein

1. put a sample of the extract in a test tube

2. add 5 drops of biuret solution

3. Blue   blue = negative

    Blue   violet/ lilac/ purple = positive 

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Test for Fats

1. put a piece of crushed/ grounded sample in a test tube

2. cover the sample with ethanol and put a stopper on the test tube

3. shake vigorously then add some distilled water and shake again

4. Clear   clear = negative

    clear   cloudy white = positive 

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Test for Vitamin C

1. A known volume of DCPIP is placed in a test tube

2. using a syringe or a burette, add the extract one drop at a time to the DCPIP

3. Blue    blue = negative

    Blue    colourless = positive

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