Food Tests- Practical

• When testing for a range of carbohydrates, we're looking at two different types: starch which is a complex carbohydrate, and reducing sugars which include glucose
• Testing for starch


  1. Break the food apart to increase surface area

  2. Mix with water and filter if food is dark in colour

  3. Add iodine solution
• Iodine solution


  Reagent used to test for starch, turns dark blue-black in the presence of starch
• Testing for reducing sugars

  1. Add Benedict's reagent (copper sulfate, sodium citrate, sodium carbonate)

  2. Heat to around 70 degrees for 5 minutes
• Benedict's reagent


  Reagent used to test for reducing sugars, turns green, yellow, orange, then red in the presence of reducing sugars
• Testing for proteins

  Add Biuret reagent (copper sulfate, sodium hydroxide, potassium sodium tartrate)
• Biuret reagent


  Reagent used to test for proteins, turns purple in the presence of proteins
• Testing for lipids/fats

  1. Rub food on greaseproof paper (leaves a greasy mark if lipids present)

  2. Shake food with ethanol, then water (forms two layers if lipids present)

  3. Add Sudan red/3 dye (red layer on top if lipids present)