Biochemical tests

• Test for reducing sugars

  1. Add excess Benedict's reagent (blue) to a sample and heat it in a water bath which is at boiling temp
  2. Positive test is will form a coloured precipitate, high concentration further the colour changing goes (brick red)
• Test for non-reducing sugars

  1. Add an acid and heat it in a water bath that's been brought to boil
  2. Then neutralise it with an alkali
  3. Add excess Benedict's reagent
  4. Positive- Will turn from blue to brick red precipitate
• Iodide test

  Add iodide dissolved in potassium iodide solution to test the sample

  If positive goes from brown/orange colour to a blue black colour

  Negative stays brown/orange
• Emulsion test for lipids

  1. Shake the test substance with ethanol for a minute so it dissolves then pour the solution in the water
  2. Any lipid will show as a milky emulsion
  3. The more lipid the more noticeable the milky colour
• Biuret test for proteins

  1. Add a few drops of sodium hydroxide solution so the solutions alkaline
  2. Add copper (II) sulfate solution
  3. Positive is purple, no protein stays blue