Food Tests- Biochemistry

Four Food tests- method plus expected results

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Testing for Reducing Sugars

Name of Test: Benedicts Test

Example of Reducing Sugars: Monosaccharies (glucose, galactose,etc)

Method: Add Benedicts reagent and boil/ heat for two minutes

Postive Result: Brick Red precipitate

Negative Result: Clear Blue solution

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Testing for Non Reducing Sugars

Test: When there is a negative result for the Benedicts Test

Example of Non Reducing Sugars: Disaccharides (Sucrose)

Method: Add hydrochloric acid and heat (breaks glycosidic bonds), Neutralise with sodium hydrogen carbonate. Add benedicts reagent and boil for 1 minute.

Postive Result: Brick Red precipitate

Negative Result: Clear Blue solution

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Testing for Proteins

Name of Test: Biuret Test

Method: Add a few drops of Biuret reagent which contains copper sulphate and potassium hydroxide- do NOT heat

Postive Result: Purple solution

Negative Result: Blue solution

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Testing for Starch

Method: Add iodine

Postive Result: Black solution

Negative Result: yellow/orange/brown solution

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