Food tests in biochemisty, OCR AS Biology, Unit 2

Here are the food tests for starch, reducing suagr, non-reducing sugar, proteins and lipids.

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  • Created by: Emily
  • Created on: 05-06-10 10:20
Preview of Food tests in biochemisty, OCR AS Biology, Unit 2

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Testing for... Description Colour change result
Starch Add iodine in potassium iodine to the From a yellow brown to blue/black
sample
Reducing Sugar Add Benedict's solution (alkaline From blue to an orange red
copper sulphate) and then heat it to precipitate (solid particles dispersed
80°C in a water bath. in the solution).
Non-Reducing Sugars This may cause a negative reducing After doing all of the steps and then
sugar test. So boil the sample with repeating the Benedict's test it
hydrochloric acid to hydrolyse any should give the same result as the
sucrose present, the cool and non reducing sugar. (From blue to an
neutralise with sodium orange red precipitate).
hydrogencarbonate solution or
sodium carbonate solution (as they
are both alkali) and then carry out
the Benedict's test again.
Protein Add biuret regent to the sample From blue to lilac
(sodium hydroxide and copper
sulphate)
Lipid Mix the sample with ethanol to At the top of the water a white
dissolve the lipid, and then add into a cloudy emulsion will form.
clean test tube with water in it.

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