RP:Food tests (B.4)(B.44)

• How are the food samples prepared?

  Mash up using a pestle and mortar, add distilled water, filter to make a solution
• What reagent is used to test for starch?

  Iodine
• what is the negative result for strach (no starch)?

  orange/brown
• what is the positive result for starch (starch is present )

  Blue /black
• what is the reagent used to test for sugars?

  Benedict's solution
• what conditions are needed for Benedict's ?

  Water bath at 80C(celsius) for 5 min
• negative result for sugars(no sugars present)

  Blue
• positive result for sugars (sugars are present)

  green -> orange -> red
• what reagent is used to test for lipids

  ethanol followed by distilled water
• what must be done to the solution when ethanol is added?

  shaken
• negative result for lipids (no lipids present)?

  no white emulsion forms
• positive result for lipids (lipids present)?

  a white emulsion forms
• what reagent Is used to test for proteins?

  Biuret solution (copper sulphate + sodium hydroxide)
• negative result for proteins (no proteins present)

  blue
• positive result for proteins ( proteins present)

  purple