Food tests

• explain benedict's test?

  • prep food sample and transfer 5cm3 to test tube
  • prep water bath - set to 75 degree Celsius
  • add benedicts solution to test tube - 10 drops using pipette
  • place test tube in water bath - use test tube holder - leave for 5 min - tube pointing away from you
  • if contains glucose
  • blue - green/yellow - low concentrations
  • blue - brick/red - high concentrations
• explain how to do Iodine solution?

  • prep food sample and transfer 5cm3 of sample to test tube
  • add few drops of iodine solution and gently shake
  • if contains starch
  • browny-orange = black or blue/black
• explain biuret test?

  • prep food sample and transfer 2cm3 of sample to test tube
  • add 2cm3 of biuret solution to sample - gently shake to mix
  • if protein present
  • blue - pink or purple
  • if not present - stays blue
• explain sudan III test?

  • prep food sample - don't filter it- transfer 5cm3 to test tube
  • use pipette - drop 3 drops of sudan III stain solution - gently shake tube
  • Sudan III - stains lipids
  • if sample contains lipids
  • mixture seperates out into two layers - top layer - bright-red
  • lipid not present - no seperate red layer