Food tests

• Reducing sugars

  add 2cm3 food sample

  add 1cm3 Benedict’s reagent

  heat mixture gently in water bath

  Colour change = positive test
• non-reducing sugars

  test with Benedict’s reagent, if negative then

  add 2cm3 of food sample to 2cm3 of dilute HCl

  heat gently in water bath

  neutralise the acid

  re-test using Benedict’s reagent, colour change means positive result
• starch

  adid a few drops of iodine to food sample

  if starch is present it’ll turn blue or black
• lipids

  dissolve the food sample in ethanol

  then add distilled water

  a white milky emulsion will form if lipids are present
• proteins

  add food sample

  add biurets solution

  solution will turn from blue to purple if proteins are present