Food tests

• Test for starch

  • Iodine solution react with starch
  • produce a dark blue-black if starch is present
  • Will work with starch dissolved in water
• Protein test

  • Buiret solution
  • Contains Sodium hydroxide and copper sulphate which gives blue colour
  • Turns violet if protein is present
  • Intensity of colour indicates amount of protein
• Test for fats (lipids)

  • soluble in ethanol but insoluble in water
  • + ethanol shake + water
  • Solution of fat in ethanol is added to water it leaves fat precipitates out as tiny droplets which produces a cloudy appearance
  • more lipids more cloudy white
• Test for sugars (Reducing sugars)

  • Glucose, maltose
  • Benedict Regent (blue)
  • Add to sample and heat it in a water bath at 75 degrees
  • IF positive test it produces coloured precipitates
  • Red- lots , pale green/yellow - little
• Test for sugars (Non-reducing sugars)

  • sucrose
  • dilute hydrochloric acid
  • heat in water bath 75 degrees
  • Add sodium hydrogen-carbonate (to neutralise it) then carry out Benedict test
  • Coloured precipitates means sugars are present