foods tests

• test for reducing sugars


  -add BENEDICT'S reagent to sample and HEAT in waterbath for 5 mins

  -RED PRECIPITATE of Cu2+ forms --> orange-brown
• test for non-reducing sugars


  -add 2cm DILUTE HCL and HEAT in waterbath for 5 mins

  -add SODIUM HYDROGENCARBONATE to neutralise

  -add BENEDICTS REAGENT and HEAT
• test for starch


  -add drops of iodine to solution

  -forms blue-black solution
• test for proteins


  -biuret test

  -add sodium hydroxide at room temperature

  -add drops of dilute copper (II) sulfate solution and mix gently

  -blue to purple = positive
• test for lipids


  -emulsion test

  -dissolve substance in ethanol and shake it

  -add water and shake

  -positive test = cloudy - white emulsion formed, light refracts through oil droplets