Action of lipase on milk - use neutrase (protease) instead?

Discussion in 'Supporting Biology' started by Snailo, Oct 8, 2019.

  1. I am assuming the answer to this question is no, but we've got milk / lipase experiments coming up and its always a bit hit or miss whether the pH drops / phenolphthalein clears. Since I have a fridge full of neutrase, and not a lot of lipase, I was wondering if this might give similar or even a more consistent pH drop. I know the protease acts on proteins not lipids, but I'm an optimist! Thought I'd check on here in case anyone has an answer before I spend ages trialling it...
  2. Hi Snailo.The whole point of this practical is to demonstrate that the Lipase breaks down Fat/Lipid tho Fatty Acids , hence the accompanying drop in pH as indicated by the Phenolpthalein changing from pink to colourless. I'd stick with the Lipase.:);)
    Last edited: Oct 8, 2019
  3. Thanks George. I was just wondering if the breakdown of the protein would also cause the pH to drop...For my purposes, I just need the pH to drop, not really bothered how!
    GeorgetheScienceTech likes this.
  4. I've never tried that but I suspect that the pKa's of the Amino Acids generated would not be low enough to cause the drop in pH to decolourise the Phenolpthalein.:)
  5. We use 0.02% cresol red in 20% IDA as an indicator which always seems to work well.
  6. We found cresol red even worse to get a colour change with than phenolphthalein. I completely hate milk/lipase practicals!! Do you use liquid or powdered lipase?
    GeorgetheScienceTech likes this.
  7. We use the Powdered form and apart from the smell it takes some time to get it into solution. If I had the choice I would go for the liquid form.:)
  8. We use powdered lipase. The most recent batch we have that we bought from timstar seems particularly good as it actually dissolves! (Came from Timstar but has Total Lab Supplies on the tub). I also use a mix of 50:50 full fat milk to single cream and give it a lot of shaking before putting it out. Seems to work well for us.