Impact of Adjusting Mash Temps After Strike?

[CascadesBrewer]

I understand the basics of mash temp (even if I get a bit lost in the science): A higher mash temp (say 156F) yields a mash with more unfermentable dextrins so you get a higher FG and lower ABV. A lower mash temp (say 150F) yields a mash with more fermentable sugars so you get a lower FG and higher ABV.

What is the impact on the characteristics of the wort if you miss your mash temp by plus or minus 5F and you spend 5 minutes adjusting the temp to your target? (you then let the mash sit for 55 minutes at the target mash temp)

Will you end up with more of the characteristics of your initial mash temp, or more of the target mash temp (where it sat for 55 of the 60 min mash), or a mix of the temps? Is it different if you hit low then raise temps vs hitting higher and lowering temps. It seems like higher temps would start to denature enzymes, especially beta-amylase, where lower temps would cause beta-amylase to start creating maltose before they started to denature, but how much of this happens in 5 minutes?

What temps cause beta-amylase to denature quickly? Palmer's book lists 149F as the upper range of the "preferred temp range" and I think the idea is that above that range it will work faster but start to denature.

I guess I always figured that if I let a mash sit for 55 min at 154F, it did not matter that my initial temp was 149F or 159F, but with a lot of talk that much of the mash conversion happens in the first 15 minutes, I am wondering if I am wrong and the initial temp has more of an impact than I thought.

 

[Qhrumphf]

There are old British recipes that involve dropping the mash temp (and sometimes the addition of more grain).

Has to do with the way the enzymes work.

Beta amylase only snips off maltose from the end of starch chains. It can't hack up the really long chains at all.

Alpha amylase, on the other hand will more randomly cleave apart large carbohydrates, producing both fermentable and unfermentable sugars.

The mash ranges often provided for single infusion mashes allow both to work because both need to work.

Step mashes allow you to optimize both enzymes in temps where one will work but the other will either work too slowly (too low for alpha) or be quickly denatured (too high for beta).

And that old British method (which I can't recall many if any breweries still using) can create HIGHLY attenuative wort by allowing alpha to hack everything apart and then beta to make it all highly fermentable.

In general, I would prefer to come in with a low mash temp and then heat. If you come in too high and then drop, you risk denaturing beta amylase (without re-adding grain to resupply otherwise denatured enzymes).

 

[CascadesBrewer]

In general, I would prefer to come in with a low mash temp and then heat. If you come in too high and then drop, you risk denaturing beta amylase (without re-adding grain to resupply otherwise denatured enzymes).

That was kind of what I was thinking. I am usually pretty good about hitting mash temps. I was brewing a small batch with my GF this weekend (her first all grain batch...and I let her come up with the grain bill and strike calcs). The target was around 154F or 156F, and we hit 162F. She was a bit worried, but I was not. We just stirred it for a bit to bring it down to the target range then sealed it in an insulated bag. It made me wonder though. I often try to hit a degree or two high, since it is harder for me to add heat than to reduce heat.

 

[SoCal-Doug]

The good news is... Over time and multiple batches, you will learn your system's characteristics and should be able to hit your mash temp within a degree or two. With every batch, take notes. Write down what happened with the temps and over how long. Review these notes and remember to adjust as needed on the next batch. Use tools like beersmith to help zero in on your strike temps. Preheat your mash tun if you like. I know people that even preheat their grains when brewing in very cold weather. You will eventually nail it.

The bad news (or at least something to keep in mind)… Conversion is not linear over time. The majority of the conversion happens (in a typical 5 gallon batch) within the first 15 to 20 minutes. Then it goes really slowly creeping toward to completion. If you miss the mark, its better to miss on the low side then bring it up.

A handy thing to have when brewing is a few ice packs in the freezer. If you strike high, toss a couple ice packs into your mash tun until the temp gets near your target, then remove them. This is also handy for brew rigs that are manually controlled, like propane where you start fiddling with the flame then get a phone call or the dog gets out. You look back at your temp and think "oh crap, i'm 8 degrees high".

 

[CascadesBrewer]

A handy thing to have when brewing is a few ice packs in the freezer. If you strike high, toss a couple ice packs into your mash tun until the temp gets near your target, then remove them.

That is actually a really good idea. I hate throwing in cool water or ice, but I could see were some ice packs could easily suck out several degrees of heat without impacting water amounts.

 

[Rev2010]

The target was around 154F or 156F, and we hit 162F. She was a bit worried, but I was not. We just stirred it for a bit to bring it down to the target range then sealed it in an insulated bag. It made me wonder though. I often try to hit a degree or two high, since it is harder for me to add heat than to reduce heat.

In that instance you could've simply dropped in a few icecubes and stirred them in. Would drop the temp towards your desired goal faster. And you'd just start with a few and after stirring them in to dissolving then take a reading. In the 2-4 minutes time it would take you to reach your correct temperature there's seriously nothing to be concerned about. I typically have it as part of my brew days step sheet to boil a tea kettle of "adjustment water" to have on hand in the event I happen to mash in a little low, which is almost never. Brewing calcs are so dang good so long as I take the grain temp and recheck (cause I usually estimate room temp since I take the grains out the fridge the night before) I nearly always hit my temp on mash in. Then that tea kettle water often serves another purpose - my dry yeast rehydration water. It's been boiled and kept in the kettle so it's sanitized, and it's usually cooled down close to temp for yeast rehydration time. If not, a few minutes in a sanitized cup in the freezer and it's at temp.

One last thing I'll note... after having used a Robobrew where I thought how much better it would be to control temps on the fly I actually found a bit more of a struggle. Why? Well... how about the time where you heat your strike water in it and it's set to strike temp (let's say 165 for example) and then you mash in and *FORGET* to hit the pause button and reset to your mash holding temp? Yeah... did that and was like wtf is my mash going up to 165??? Derp. It's so easy to overlook something like that. Yes, user error, but very easy to miss on a busy brew day. Plus there's the issue of the temp probes reading quite a bit off the temp of the middle of the mash and raising the mash temp, or letting it lower, several degrees.


Rev.

 

[dmtaylor]

Based on my own research, the exact mash temperature matters very little in the Goldilocks range of about 148-154 F. Outside of that range, there are some minor effects but not as much as you might expect. If your favored mash temp is in that range, you won't see much if any effect if the temperature moves to the opposite end of the range within your mash time. Slightly above that range starting at about 156 F you'll see the beta denature with slight reduction in attenuation. Below the range is okay but you might just want to mash a little longer to ensure you're getting the benefit of the alpha. But really, unless you're mashing at >160 F or <145 F, you're not going to see a huge impact anywhere in between.

EDIT: I see you struck in at 162 F. Yeah, that was a bit high. I would worry about denaturing the beta very quickly at that temp. On the other hand... it might turn out okay still if you mashed for a longer time until the alpha chainsaw really made a lot of smaller bits of the starches. In any case, I think the solution is a longer mash time if you're outside the Goldilocks range on either the high or low end. I can't prove it (yet) but that's my thinking on the topic at this time.

 

[CascadesBrewer]

Some searching for terms like "beta amylase denature" turned out some discussion threads and some articles that got way more into science than I care to venture right now.

This thread had some good info (and links to some other good info). There is a graph of beta-amylase denaturing time for different temps that does make me worried that I should have been worried about my high mash in temp.
https://www.homebrewersassociation.org/forum/index.php?topic=13720.0

Oh well. By the way the Milk Stout that she/we brewed was supposed to be around 1.054 but came in around 1.044 due to low mash efficiency (hmmm...wonder why) and less boil off than planned. Oh well...more beer and less drunk.

 

[RM-MN]

What is the impact on the characteristics of the wort if you miss your mash temp by plus or minus 5F and you spend 5 minutes adjusting the temp to your target? (you then let the mash sit for 55 minutes at the target mash temp)

The real answer is nobody knows for sure. If your grains were milled very fine, the conversion happens very quickly and if too warm, the enzymes are denatured before they can do anything more. With coarser milling the enzymes can't begin their work until the starch gets gelatinized (wet in simpler terms) and that then slows the mash so that taking 5 minutes to bring the temperature from 162 to 156 won't have a big impact as the mash will take much more time, perhaps up to 2 hours if the crush is really coarse. If the temperature was 5 degrees low you simply get a more fermentable wort as the beta amylase won't denature as quickly and as the temperature is brought up the alpha amylase will start to work faster.

 

[Coffeeturnal]

I just did an unintentional experiment on this recently. Don't recall what I overshot to, but it was well over 160. I was going for 158 because I wanted a really unfermentable wort.

After an hour of mashing, almost no conversion had happened. I added a bit of alpha enzyme I had picked up forever ago and that got the mash done in ~20 more min (I had got the temp down where I wanted.

OG was 1.037 (some other issues caused this to be lower than planned as well, but not relevant here)
FG was 1.017

It actually came out really nice... Not sure that if I'd try recreating this, but the slight extra sweetness balanced this beer in a way that I hadn't achieved before.


TL;DR
Overshooting your temp can denature the enzymes and create a super unfermentable wort. Might get lucky and have it turn out well, but be careful.

 

[CascadesBrewer]

FYI...I was over at my GFs place looking at the notes and talking about why were were off on a few numbers. Looking at the recipe that called for 2.5 lbs of 2-row, she realized that she only purchased 2 lbs (sold in 1 lb bags). LOL! Leaving out 20% of your base malt will impact a beer (the recipe only had 8 oz of specialty grains).

Edit: After plugging that reduced grain bill and increased fermenter volume into BeerSmith it says around a 67% overall efficiency. That seems pretty decent for a full volume mash with grain crushed using the store's mill. GF keeps saying "if it is bad I will dump it"...but I am thinking she will have a very nice 4% ABV Stout.

I could make fun of her...but I recently threw and extra 4 lbs of grain into an IPA recently and it took me several days to realize the mistake!