Food tests practical - biology

• Carbohydrates, lipids and proteins


  Biological molecules (molecules found in living organisms)
• Testing for Sugars using Benedict's Reagent

  1. Add Benedict's reagent (blue) to sample

  2. Heat in 75°C water bath

  3. Colour change from blue to green, yellow, orange or red indicates presence of reducing sugars

  4. Higher concentration of reducing sugars results in more colour change
• Testing for Starch using Iodine

  1. Add iodine solution to sample

  2. From browny-orange to Blue-black colour indicates presence of starch

  3. No colour change indicates no starch
• Emulsion Test for Lipids

  1. Shake test substance with ethanol until dissolved

  2. Pour into water

  3. Milky emulsion indicates presence of lipids

  4. More lipid results in more noticeable milky colour
• Biuret Test for Proteins

  1. Add potassium hydroxide solution to make alkaline

  2. Add copper(II) sulfate solution

  3. Purple colour indicates presence of protein

  4. Blue colour indicates no protein