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Food Tests

Brief description of main food tests.

Brigita Biondic

on 22 November 2016

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Transcript of Food Tests

1. Glucose: Benedict Test
Lipids / Fats:
When a sample containing fats is pressed or rubbed on a clean white sheet of paper, a greasy spot (translucent spot) appears.
Biuret solution is used to identify the presence of protein. Biuret reagent is a blue solution that, when it reacts with protein, will change colour to mauve-purple.
Major food types are:
1: Carbohydrate
3: Proteins
2. Starch: Iodine Test
Positive test gives dark purple - black colouring on the sample.
1.Take small amount of crushed food sample or 10 drops of aqueous solution of the sample in a test tube.
2. Add 3-4 drops of iodine solution.
3. Note any color change.
Benedict's solution is a clear blue solution that in the presence of simple sugars will change color to green, yellow, and brick-red, depending on the amount of sugar.
1. To a test tube, add food sample to be tested.
2. If testing more than one liquid, label each test tube with a marker.
3. Add 10 drops of Benedict's solution to each test tube.
4. Carefully heat the test tubes by suspending in a hot water bath for five minutes.
5. Note any color change.
Spot test using a filter paper:
1.Take a food sample to be tested and press or rub it on a clean white sheet of paper.
2.Hold it against light to see if the paper become transparent or not.
Biuret Test:
1.Take small amount of crushed food sample in a test tube.
2.If testing more than one liquid, label each test tube with a marker.
3.Add 3 drops of Biuret reagent solution to each test tube. Shake gently to mix.
4.Note any color change.
Biuret Solution contains the same amount of sodium hydroxide and copper sulfate solution.
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