Food Tests

Benedict's Test for Reducing Sugars

• Pour 2cm³ of solution sample solution into a test tube and add an equal volume of Benedict's solution. 
• Shake the mixture.
• Heat test tube in a boiling water bath for 5 minutes.
• Record observation after 5 minutes.

Colour of precipitate and the corresponding amount of reducing sugar present

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Biuret's Test for Proteins

• Add 2cm³ of sample solution to a clean test tube and add 2cm³ of dilute sodium hydroxide solution.
• Shake the mixture.
• Add 1% copper (II) sulphate solution, drop by drop. Shake mixture after every drop and observe the colour change. 
• If mixture remains blue, no protein is present.
• If mixture turns violet/purple, protein is present. 

Iodine Test for Starch

• Add 2cm³ of sample solution to a clean test-tube, followed by a few drops of iodine solution.
• Observe the colour change.
• If mixture remains brown, no starch is present.
• If mixture turns blue black, starch is present.

Ethanol Emulsion Test for Fats

• Add 2cm³ of sample solution to a clean test tube and add 2cm³ of ethanol.
• Shake mixture thoroughly.
• Add 2cm³ of water into the test tube and shake. 
• Record the observation.
• If mixture remains clear, no lipid is present.
• If a white emulsion was obtained, lipid is present.