[oscarvan]

OK, I'm having a hard time getting all my thermometers on the same page. I'll have to invest in a REAL one and then calibrate the dial thermometers in the HLT and MLT. The spread is as much as 10º  Also, with the 70Q Coleman Extreme I am not getting much  of a temperature drop on infusion....

Using the consensus method I think the mash stabilized at 155, which is where I wanted it. But, there is the possibility that for a few minutes it was at, or near 170º Now I know the conversion process stops at that point, but is that because the enzymes can't function anymore, or does 170º actually kill them?

I guess I'll have the answer when I do my gravity readings on lautering, but in the meantime I would like to hear some input.... thanks.

[tschmidlin]

170F is enough to unfold the enzymes (can't function), but it does NOT happen immediately.  I would also expect it to be mostly reversible (doesn't kill them) at that temperature, especially after just a short period of time.

[Kaiser]

The denaturation of enzymes is a function of temperature and time. So being at 170 for a short amount of time would not have killed them, but depending on how long actually was at that temp the b-amylase, which is the main creator of fermentable sugars, may have taken quite a hit. The result might be less fermentable wort.

Kai

[tschmidlin]

Kai, do you have a source for the Tm of barley beta- and alpha-amylase?  It might be in one of my books, but google can't find it for me.

[bluesman]

I'll have to invest in a REAL one and then calibrate the dial thermometers in the HLT and MLT. The spread is as much as 10º 

Great idea!

I use a lab thermometer that is calibrated to NIST traceable standards and the great thing about is that they are fairly inexpensive. I think I paid less than $20 for mine.

[oscarvan]

We're talking a few minutes here. Having the conflict I went with the hottest temp and stirred the mash lid off until it came down, but I may in fact be too cool now.

I REALLY need some decent thermometers. I can't control what I can't measure accurately....these $7 dial thermometers are toys.

Anyone have a source for accurate tools?

[bluesman]

Here ya go.

http://vwrlabshop.com/vwr-general-purpose-thermometers/p/0013362/

edit: corrected link

[a10t2]

Kai, do you have a source for the Tm of barley beta- and alpha-amylase?  It might be in one of my books, but google can't find it for me.

About ten minutes at 70°C. http://aem.asm.org/cgi/content/full/71/7/3709

bluesman, I don't think 5°F divisions are going to be good enough for mashing. I use one of these: http://www.arborsci.com/prod-Digital_Thermometer-61.aspx

[tom]

Once enzymes are denatured it is irreversible.

[tschmidlin]

Kai, do you have a source for the Tm of barley beta- and alpha-amylase?  It might be in one of my books, but google can't find it for me.

About ten minutes at 70°C. http://aem.asm.org/cgi/content/full/71/7/3709

That might not be directly comparable.  Those aren't barley enzymes, they're from a thermophilic bacteria so we can expect different physical properties.  For example the favored pH range is different.  They're also looking at purified recombinant protein, which is not the same as mash conditions where other cellular constituents are present.

[tschmidlin]

Once enzymes are denatured it is irreversible.

That is true for some proteins, but certainly not for all.

[Kaiser]

Even I didn’t bother looking at my own site . Here are some graphs that I collected over time:

http://braukaiser.com/wiki/index.php/Starch_Conversion#Temperature_and_Time

It’s inherently difficult to put a time on this. Not only because we need to give a rate of denaturation instead of an actual time, but also because it depends on more factors than just temperature. Mash thickness for example is also one of them.

Kai

[bluesman]

bluesman, I don't think 5°F divisions are going to be good enough for mashing. I use one of these: http://www.arborsci.com/prod-Digital_Thermometer-61.aspx

Here's the link I actually meant to post for thermometers. 

http://vwrlabshop.com/vwr-general-purpose-thermometers/p/0013362/

[denny]

I use this one to calibrate my brewing thermometers.

http://vwrlabshop.com/vwr-lollipop-thermometers/p/0025608/

[tschmidlin]

Even I didn’t bother looking at my own site . Here are some graphs that I collected over time:

http://braukaiser.com/wiki/index.php/Starch_Conversion#Temperature_and_Time

It’s inherently difficult to put a time on this. Not only because we need to give a rate of denaturation instead of an actual time, but also because it depends on more factors than just temperature. Mash thickness for example is also one of them.

Kai

Thanks Kai.  Those activity graphs are great, what is the original source for the data?  Your website is really impressive, as always, there's tons of stuff on there.

What I'd really like to see though, is activity curves for enzymes held at 70C for x minutes then cooled to different temps.  It would give an indication of how rapidly it denatures and the reversibility of denaturation, that's what's important for oscarvan's question.