Test for Reducing sugars and non reducing sugars and test for starch


Test for Reducing sugars

Reduction is a chemical reaction involving the gaining of electrons. A reducing sugar therefore can donate electrons to another chemical, in this case benedicts reagent.

  • Add food sample you want to test in a liquified form into a test tube
  • add an equal volume of Benedicts reagent
  • heat the mixture
  • if solution is orange/brown reducing sugar is present.
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Test for non reducing sugars

  • put sample of food in liquid form into a test tube
  • add benedicts reagent
  • heat test tube
  • if solution remains blue reducing sugar IS NOT present
  • add another sample of the food into a new test tube
  • and add acid ( hydrochloric acid) as it will hydrolyse any disaccharide present
  • heat
  • then add an alkaline ( hydrogencarbonate solution) to nuetralise acid( benedicts reagent doesnt work under acidic conditions)
  • retest the solution by heating with benedicts reagent
  • if non reducing sugar is presnt solution will turn orange/brown due to reducing sugars that were produced from the hydrolysis for the non reducing sugar.
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Test for starch

  • place sample being tested in a test tube
  • add two drops of iodine solution and shake or stir
  • presence of starch is indicated by blue black colouration.
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