Biology‎ > ‎

Food Tests

 TestMethod
Observation
 Conclusion
Benedict's Test - Reducing sugar
  •  Add 2cm3 of Benedict's solution to 2cm3 of the solution in a test tube
  • Shake the test tube to mix
  • Place the test tube in boiling water for 5 minutes
  •  Positive result: a blue-green/yellow/orange/brown/red/brick-red precipitate is formed
  • Negative result: the mixture remained blue in color
  •  reducing sugar is present
  • reducing sugar is absent
Iodine test - Starch
  •  Add 2 to 3 drops of iodine solution to the substance
  • Positive result: a blue-black color was observed
  • Negative result: the brown color of the iodine solution remained
  •  Starch is present
  • Starch is absent
Biuret test - Proteins
  •  Add 2cm3 of sodium hydroxide (NaOH) to 2cm3 of the substance in a test tube
  • Shake the test tube to mix
  • Add 1% copper sulphate solution (CuSO4) dropwise, shaking the tube after each drop
  •  Positive result: the mixture turned from light-blue to violet
  • negative result: the mixture remained light blue in color
  • Protein is present
  • Protein is absent
Ethanol emulsion test - fatsFor liquid sample:
  • Add 2cm3 of ethanol to 2cm3 of the substance in a test tube and shake to mix well
  • Add 2cm3 of water to the mixture and shake to mix well
For solid particles:
  • Cut/crush the solid into small pieces and add 2cm3 of ethanol in a test tube
  • Decant the ethanol into another test tube and add 2cm3 of water.
  • Mix well
  •  Positive result: homogeneous (clear) solution was formed with ethanol
  • Negative result: homogeneous (clear) solution was formed with ethanol
  • the solution remained clear upon mixing with water
  • Fat is present
  • Fat is absent


Comments