20 min conversion at 140F?

[riderkb]

I did a batch today that had a negative starch test after 20 minutes at 140 F. Normally it takes most of an hour. Sometimes I don't get full conversion until I bump up to a higher temp to finish it off.

Two things were different: Kolsch malt and pH. This was my first time using Kolsch malt, which I expected to be a lot like Pilsner malt. I've done the same mash schedule with many different malts and always get similar conversion rates. Normally the pH comes in at 6.0 or 6.1, but today I added acid to bring it down to 5.5.

Anyone else see much faster conversions at lower pH?

 

[ArcLight]

>>Anyone else see much faster conversions at lower pH?

Seems highly unlikely. Enzymes react much slower at lower temperatures that are below their peak point.

 

[riderkb]

My first thought was a miscalibrated pH probe or thermometer. The pH probe checked out at 3.6, 4.0, 4.7, and 7.1. The thermometer reads 1C in ice water and 99C in boiling water. At mash temps the error is just a few tenths.

 

[Denny]

I think something screwed up in your test. That's why I stopped doing them a long time ago.

 

[riderkb]

I quit doing the starch test for a while, too. But now I'm pulling a mash sample and cooling it to check the pH, so I've been testing for starch at the same time.