Fermentability/Mash Temps etc

Search for BrewCiper. Vikeman will hook you up.

Your 170 mash is interesting though - at that temp all the enzymes that convert starch to fermentable sugars should be denatured. How confident are you in that temperature? ie was it that temp entirely from strike to boil, or was there any time where it was lower for any significant amount of time? are you sure it was 170 deg F everywhere in the mash, or just at one spot?

 

While I could be wrong, my understanding is that a 170F mash will give you damn close to 0% conversion. The conclusion? You need to correct your method for measuring mash temp. It's likely you simply hit a hot spot in the mash bed.

To answer your original question - well, I can't. I select a mash temp based on high, med, low fermentation, suitable to the style of beer I'm brewing. I haven't yet documented the results of different temps and, frankly, I don't care enough to develop that level of control. What I'm doing is good enough for me. Contrary to popular opinion, this is art, not science. And I'm lovin' it!

Edit: ok, maybe it's a bit of Science, too. Perhaps I should have said "this is more art than Science"

 

Like mattbk said, you could try the BrewCipher spreadsheet. Download here.
It's a general purpose brewing sheet that does what you're asking (among other things) by considering some mash parameters, grist, and yeast strain. Try it, compare results to your actual results, and dial-in the 'power factor' (if necessary) to give you better predictions on future batches.

I have to say, if you really single infusion mashed at 170F, I'm surprised you got signifcant conversion at all (nevermind attenuation). How certain are you of your mash temp? Calibrated thermometer?

Edit: I see some of this was redundant. Though I'll add... a 170F hot spot would still indicate a pretty dang hot mash (or bad thermometer), unless the temp was measured before stirring thoroughly.

 

When is the last time you calibrated your thermometer?

 

This should help. I recall a buddy in my homebrew club was also pissed off that his beers never fermented out and got stuck fermentation. He comes to find out his thermometer was off by 10 degrees, so when he was mashing at 152 it was actually 162.

 

Amen...Brother Mike.

 

At 170F the Alpha will still be active, but it is just turning starches to dextrins. No Beta for sure (so I agree, Matt).

I suspect the thermometer.

 

I dealt with this exact issue.

 

I find it's a good idea to calibrate those long meat thermometers often with a glass thermometer. Its seems they always get bumped around when clipped onto the side of the kettle and become less reliable. It's not a terrible idea to do this prior to every brew session.

I've made practice of doing it anytime I'm doing a starter as I'll be boiling stuff anyway.