Mash temperature and final gravity

I’ve always wondered this but have not done the experiment to find out. I’m sure some of you have. I understand that mash temperature will select for non-fermentable versus more fermentable sugars. But will this actually affect final gravity points or just mouth feel? For instance if I brew the exact same recipe on the exact same equipment and mash one batch at 148deg and one batch at 158, will the final gravity points be significantly different?

Mike Karnowski of Green Man in Ashville NChas recently posted some info about that, but I’ll have to dog up his conclusions.  I recall that the two were unconnected, but I can’t recall which was affected by mash temp.

I’ve always felt that mashing @ sub 150F I got lower FGs than above 150. I never experimented with the same grist just to test for that though.

I sent Mike an email asking him to remind me where to find his results.  I’ll let ya know what I hear.

Thanks Denny, conceptually I would think if there are more fermentable sugars around, more would be turned in the ETOH AND Co2 and the final gravity would be less but I don’t know if it really works out that way.

My experience is low temp equals lower fg.

I think it depends on the malt used and if it has a bunch of Alpha and Beta. The studies that Kai and Greg Doss did for Pils malt said 152-153F gave the best attenuation. There are data that say lower is better, maybe for Pale Ale Malt with is low in Alpha. For “hot” US malts with high Alpha and Beta, it might be around 158F, but that is speculation on my part.

Waiting for my copy of Malt to see if Mr. Mallett covers this.

My answer is Yes there will be a difference,  No it will not be significant. At least not with most modern malts. But I suppose it depends on what significant means. For example if 158 gets you to 1.012, 148 might make the exact same grain bill go to 1.010.

I have recipe that fermented from 1.039 to 1.003 at 148° and to 1.006 at 158°. That’s semi-significant, but only one set of data points.

I think this is pretty much accurate. I accidentally mashed my APA grist at 77°C and it still attenuated 74% ADF. The norm (at 67°C) is 80%.

A little over 170F? Wow!

Here’s the reply I got from Mike.  The book he mentions is “Homebrewing: Beyond the Basics”.

It’s in my book, we also did a blind triangle tasting at the brewery when one of our beers finished at 1.020 instead of the usual 1.010 and nobody could pick it out. My theory is that long chain sugars from mashing high aren’t perceived as being sweet (just taste some malto dextrin powder) or contributing body. On the other hand, residual simple sugars from an incomplete fermentation will taste cloyingly sweet.

Cool, interesting.  Love this forum.

very interesting

Just to clarify that quote, it’s in Mike’s book, not mine.

Wow…that’s pretty interesting. So what is the take away from this?  Should we be concerned about mash temps…or at least as much as we are?  What is more important is the fermentation process (oxygenation, temp control, healthy yeast, etc) so that a COMPLETE fermentation takes place?

My take on this is that mash temp precision is less important with modern malts than it was once upon a time. But old news dies slow. As to which is more important for attenuation, I think the most important thing is a proper sized pitch of healthy yeast of a strain that attenuates at the rate you desire, pitched into properly oxygenated wort that is kept at tge proper temp until it is all done.

Testing this with Denny ( I posted this on his wall) I mashed a blue moon clone in the mid 160’s, and a pilsner in the mid 150s.

FG on the blue moon was 1.020

Fg on the pils was like 1.015

The blue moon tasted as it always does when it finishes at 1.014, and the pils had too much body, but was not sweet normally Fg for this beer was 1.011.

I kept the Blue moon, and gave away the pils.