7.1c Food- Part 3 (Food Tests)

• What is the test for starch?

  Iodine solution
• What is the test for sugar?

  Benedict's reagent
• What is the test for fats?

  Ethanol
• What is the test for protein?

  Biuret solution
• Method of testing starch?

  Add the iodine solution directly to the substance to be tested and look for a colour change. If it stays brown it is negative and if it changes to black it is positive.
• Method of testing sugar?

  Add Benedict's reagent to the solution to be tested. Heat for two minutes in a water bath at boiling point and look for a colour change. If it stays blue there is no sugar, and if it changes to red it contains sugar, but if it turns green/yellow/orange it has less sugar.
• Method of testing fats?

  Add ethanol to the solution to be tested and shake thoroughly. Then add water and look for a colour change. If it stays clear it has no fats and if it turns cloudy white it has fats.
• Method of testing protein?

  Add Biuret solution to the solution to be tested and look for a colour change. If it stays pale blue it doesn't contain protein, if it changes to purple it contains protein.
• If the iodine stays brown it has no starch, if it changes to black it contains starch.
• If the Benedict's reagent stays blue it doesn't contain sugar, if it turns red it contains sugar, if it turns green/yellow/orange it has less sugar.
• If the ethanol stays clear it doesn't contain fat, if it changes to cloudy white it contains fats.
• If the Biuret solution stays blue it doesn't contain protein, if it changes to purple it contains protein.