Peter Sigsworth
COMMITTEE
Just coming to the end of my 'soluble starch' which I make up as 2g dissolved in 100ml distilled water heated to produce a clear liquid.
I use this in amylase practicals and it gives a clear (in both meanings of the word) complete end result.
Made up some 2% starch today using the same recipe but with a new bottle of 'soluble starch' - wouldn't clear fully at all when heated - so although it cleared a bit it remained cloudy.
Did a test run with - usual concentrations - 5ml 0.1% Pancreatin added to 5ml if the new starch solution. Samples every 30s with iodine solution.
It took 4 minutes for the starch to start to disappear but then (unlike my old stuff) it never completely stopped testing positive. I could see small dots of starch which produced a slight positive result which went on for 20 minutes - so not as clear end result as there was with the old stuff. I added the iodine into the reacting tube and it produced a very dark brown solution ie a positive result all be it not completely blue/black. So still starch present after 30 minutes.
I can only explain this by questioning the purity of the new 'soluble starch' - Because it will not clear there must be a proportion of the starch which is not soluble, I guess must have some longer chain starch molecules which stay suspended (making it cloudy) and take much longer to break down.
Does anyone know where I can get proper 'soluble starch' from. What supplier do you use that give you go clear end results.
I use this in amylase practicals and it gives a clear (in both meanings of the word) complete end result.
Made up some 2% starch today using the same recipe but with a new bottle of 'soluble starch' - wouldn't clear fully at all when heated - so although it cleared a bit it remained cloudy.
Did a test run with - usual concentrations - 5ml 0.1% Pancreatin added to 5ml if the new starch solution. Samples every 30s with iodine solution.
It took 4 minutes for the starch to start to disappear but then (unlike my old stuff) it never completely stopped testing positive. I could see small dots of starch which produced a slight positive result which went on for 20 minutes - so not as clear end result as there was with the old stuff. I added the iodine into the reacting tube and it produced a very dark brown solution ie a positive result all be it not completely blue/black. So still starch present after 30 minutes.
I can only explain this by questioning the purity of the new 'soluble starch' - Because it will not clear there must be a proportion of the starch which is not soluble, I guess must have some longer chain starch molecules which stay suspended (making it cloudy) and take much longer to break down.
Does anyone know where I can get proper 'soluble starch' from. What supplier do you use that give you go clear end results.