Food Test Practicals

• Food tests

  1. Prepare food sample

  2. Dissolve in distilled water

  3. Filter solution
• Sugars

  Small units that all carbohydrates are made of
• Types of sugars

  • Reducing sugars
  • Non-reducing sugars
• Benedict's test for reducing sugars

  1. Prepare food sample

  2. Transfer 5cm3 to test tube

  3. Add 10 drops benedict solution

  4. Heat in 75°C water bath for 5 mins
• Benedict's test results

  • Blue = no reducing sugars
  • Green, yellow, brick red = reducing sugars present
• Starch


  A type of carbohydrate, larger and more complex molecule than sugars
• Iodine test for starch

  1. Add 5cm3 food sample

  2. Add iodine solution

  3. Shake gently
• Iodine test results

  • Browny orange = no starch
  • Blue-black = starch present
• Biuret test for proteins

  1. Add 2cm3 food sample

  2. Add 2cm3 biuret solution

  3. Shake gently
• Biuret test results

  • Blue = no proteins
  • Pink/purple = proteins present
• Edexcel biuret test for proteins

  1. Add potassium hydroxide

  2. Add copper sulfate
• Sudan 3 test for lipids

  1. Add 5cm3 food sample

  2. Add 3 drops sudan 3 stain

  3. Shake gently
• Sudan 3 test results

  • Bright red layer = lipids present
• Edexcel emulsion test for lipids

  1. Add 2cm3 ethanol, shake vigorously

  2. Add equal volume distilled water
• Emulsion test results

  • Cloudy white = lipids present
  • No cloudy white = no lipids