pratical 1

• 1. Put some of the food sample into a test tube.
  2. Add a few drops of iodine solution to the food sample using a pipette.
  3. If starch is present, the solution turns from brown to blue-black. Note any colour change in atable of results.
• 1. Add an equal volume or excess of Benedict’s solution to the food sample in a test tube.
  2. Place in a hot water bath for a few minutes.
  3. If reducing sugar is present, a brick red precipitate is formed. If reducing sugar is absent,the solution remains blue. Note any colour change in a table of results.
• 1. Add a few drops of Biuret’s reagent (sodium hydroxide and copper (II) sulphate) to the food sample in a test tube.
  2. Shake the solution to mix and wait for a few minutes.
  3. If protein is present, the solution turns from blue to purple.
• 1. Add a few cm3​ ​of ethanol to the food sample.
  2. Pour this mixture into a test tube of equal volumes of distilled water.
  3. If lipids are present, a white emulsion is formed on the surface of the mixture.
  4. This is called the emulsion test.