Author Topic: does gradual heat loss in mash affect fermentability of wort?  (Read 2350 times)

Offline chinaski

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does gradual heat loss in mash affect fermentability of wort?
« on: December 17, 2015, 03:46:00 AM »
I've always wondered:
Given that increasing mash temp will decrease fermentability of wort of a single infusion mash, what happens if you achieve a higher initial mash temp- say 156F, but the mash looses heat over an hour and ends up after an hour at 148F?  Is fermentability set by the initial temp or can it change if temps go down?  I suspect that if temps decrease in this scenario, the fermentability would increase because the enzyme (I forget which amylase) that influence higher fermentability is still present and will react to the decreasing temp.

Anyone know the answer?
Thanks!

Offline ccfoo242

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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #1 on: December 17, 2015, 04:04:39 AM »
I think the enzymes that are active at lower temperatures denature at the higher temperatures and the temp shift downward would have to happen quickly before they denature completely. But a slow lowering of the temp over an hour, like what happens in a blue cooler, wouldn't result in a more fermentable wort. Just my guess, though.
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Offline klickitat jim

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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #2 on: December 17, 2015, 04:53:28 AM »
Here's a couple charts.



The thing to keep in mindvis that these enzymes dont denature like a light switch. It happens over time. If you mashed in at say 158 and the temp dropped over a couple hours to 142, I would think that wort would be significantly more fermentable than a wort held at 158 the entire time.

Offline Joe Sr.

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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #3 on: December 17, 2015, 03:30:07 PM »
Didn't Kai or someone do a mash with declining temp and post a chart?  I'd look, but I'm too lazy.

One thing to consider is that at lower temps, the conversion happens more slowly.  So you'd probably have to extend your mash to see any significant impact.  I know that if the temp drops significantly on my BIAB stove top mashes (non-insulated) I get very poor conversion.  But I think that if I extended the time of the mash, it would improve (although the temp would keep dropping unless I heated it).  I know if I keep the temp up/steady I get better conversion (duration held constant).
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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #4 on: December 17, 2015, 03:39:35 PM »
what happens if you achieve a higher initial mash temp- say 156F, but the mash looses heat over an hour and ends up after an hour at 148F?


If you mash in a cooler, that won't happen. You'll lose a degree or two F, which is negligible to the end product.
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Offline stpug

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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #5 on: December 17, 2015, 03:53:46 PM »
It seems like it's hard to definitively say one way or another. I experienced significant slipping mash temps early on in AG brewing that seems to be the cause of over-attenuation. My experience would indicate that significant slipping mash temps do cause overly fermentable wort BUT the circumstances are probably equally as important.  Time to denature, amount of temp drop, how quickly temps drop, duration of mash, etc all play a factor, and is why I think it's hard to have a definitive answer to the question.

BTW, I use a cooler and my temps slipped significantly in the early days of AG brewing so even with a cooler it can happen.

I've resolved nearly all temp slippage by simply using a temp refreshing step at the midpoint during mashing. I simply reserve 0.5-1.5 quarts of my strike water in a pan. At the midpoint in mashing (usually about 30minutes) I heat it to boiling and stir it into the mash. This gives me the opportunity to 1) stir up my mash, 2) check how much temp drop I've had, and 3) refresh the mash temp to where I want it. Additionally, I assume that whatever slippage has happened has only lasted a short while.

At least, that's been my experience.

Offline HoosierBrew

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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #6 on: December 17, 2015, 04:04:34 PM »
It seems like it's hard to definitively say one way or another. I experienced significant slipping mash temps early on in AG brewing that seems to be the cause of over-attenuation. My experience would indicate that significant slipping mash temps do cause overly fermentable wort BUT the circumstances are probably equally as important.  Time to denature, amount of temp drop, how quickly temps drop, duration of mash, etc all play a factor, and is why I think it's hard to have a definitive answer to the question.

BTW, I use a cooler and my temps slipped significantly in the early days of AG brewing so even with a cooler it can happen.

I've resolved nearly all temp slippage by simply using a temp refreshing step at the midpoint during mashing. I simply reserve 0.5-1.5 quarts of my strike water in a pan. At the midpoint in mashing (usually about 30minutes) I heat it to boiling and stir it into the mash. This gives me the opportunity to 1) stir up my mash, 2) check how much temp drop I've had, and 3) refresh the mash temp to where I want it. Additionally, I assume that whatever slippage has happened has only lasted a short while.

At least, that's been my experience.


I've never experienced a big temp drop in coolers - I've used used the Coleman Extreme type coolers for years. How much of a drop do you see, out of curiosity ?
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Offline Wort-H.O.G.

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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #7 on: December 17, 2015, 04:10:09 PM »
mash indoors or outsoors with that cooler? i've never done a mash outside in cold temps, but as far as indoors, mine holds within couple degrees over 60-75 minutes
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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #8 on: December 17, 2015, 04:15:02 PM »
I use a huge 70 quart coleman extreme cooler and never have temp drop when mashing for 60-90 min, I actually have some temp raise if I don't mash in long enough and stir everything up for at least 5 minutes before shutting the lid


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Offline stpug

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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #9 on: December 17, 2015, 04:35:56 PM »
It seems like it's hard to definitively say one way or another. I experienced significant slipping mash temps early on in AG brewing that seems to be the cause of over-attenuation. My experience would indicate that significant slipping mash temps do cause overly fermentable wort BUT the circumstances are probably equally as important.  Time to denature, amount of temp drop, how quickly temps drop, duration of mash, etc all play a factor, and is why I think it's hard to have a definitive answer to the question.

BTW, I use a cooler and my temps slipped significantly in the early days of AG brewing so even with a cooler it can happen.

I've resolved nearly all temp slippage by simply using a temp refreshing step at the midpoint during mashing. I simply reserve 0.5-1.5 quarts of my strike water in a pan. At the midpoint in mashing (usually about 30minutes) I heat it to boiling and stir it into the mash. This gives me the opportunity to 1) stir up my mash, 2) check how much temp drop I've had, and 3) refresh the mash temp to where I want it. Additionally, I assume that whatever slippage has happened has only lasted a short while.

At least, that's been my experience.


I've never experienced a big temp drop in coolers - I've used used the Coleman Extreme type coolers for years. How much of a drop do you see, out of curiosity ?


I mash indoors with my batch sparging cooler setup. Using a 5 gallon rubbermaid water cooler I was seeing probably about 6°F drop over the course of an hour, but I believe several things contributed to this. As an example, I'd start at 154 and end up at 148 (which puts the midpoint about 151F), and most likely I went from 154 to 151 fairly quickly (within 10 minutes) and no where near as quickly from 151 to 148 (remaining 50 minutes).

I wasn't accounting for the immediate loss of heat from the cooler equalizing with the mash (thus the reasoning for the quick initial loss). Obviously, I wasn't preheating the cooler in any fashion. I wasn't aware that my (probably most) lids don't seal very well. Lid was not insulated. And, I prefer to take an average measurement of my MLT temperature as opposed to spot temps (explained below). Long story short, lots of mash temp loss and over-attenuation of many beers. Since realizing the limitations of my system and resolving those items that I could easily resolve, I have not experienced such over-attenuation that I once did (with the exception of using new yeast strains that over-perform what the manufacturers state - 1187!).

As for my temperature taking, I would see what I would consider significant difference in a temperature reading from the center of the mash versus a reading from the mash near the cooler wall (a couple degrees). Enough so that I decided the best way to get a reliable and reproducible reading was to stir up the entire mash (walls with center, top with bottom) while watching the thermometer (rt600c). This approach works for me and I feel that the mixing of the "microclimates" inside the MLT gives me an accurate picture of what kind of environment is being produced so I have a better idea of what kind of enzymatic activity could be taking place.

Since refining my process, which can certainly seem overly complex/critical/dorky, I am seeing attenuation in the ballpark of what I'd expect - most times. Sometimes I'm thrown a curveball that I try to figure out (dark, roasty beers), or a new-to-me yeast strain that I need to become familiar with, but it's all part of the fun of homebrewing for me.

Offline Rhoobarb

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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #10 on: December 17, 2015, 04:36:57 PM »
I mash in a red cooler.  Red coolers have it all over those pesky blue coolers.

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Offline Joe Sr.

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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #11 on: December 17, 2015, 04:55:18 PM »
I mash indoors with my batch sparging cooler setup. Using a 5 gallon rubbermaid water cooler I was seeing probably about 6°F drop over the course of an hour, but I believe several things contributed to this. As an example, I'd start at 154 and end up at 148 (which puts the midpoint about 151F), and most likely I went from 154 to 151 fairly quickly (within 10 minutes) and no where near as quickly from 151 to 148 (remaining 50 minutes).

I wasn't accounting for the immediate loss of heat from the cooler equalizing with the mash (thus the reasoning for the quick initial loss). Obviously, I wasn't preheating the cooler in any fashion. I wasn't aware that my (probably most) lids don't seal very well. Lid was not insulated. And, I prefer to take an average measurement of my MLT temperature as opposed to spot temps (explained below). Long story short, lots of mash temp loss and over-attenuation of many beers. Since realizing the limitations of my system and resolving those items that I could easily resolve, I have not experienced such over-attenuation that I once did (with the exception of using new yeast strains that over-perform what the manufacturers state - 1187!).

As for my temperature taking, I would see what I would consider significant difference in a temperature reading from the center of the mash versus a reading from the mash near the cooler wall (a couple degrees). Enough so that I decided the best way to get a reliable and reproducible reading was to stir up the entire mash (walls with center, top with bottom) while watching the thermometer (rt600c). This approach works for me and I feel that the mixing of the "microclimates" inside the MLT gives me an accurate picture of what kind of environment is being produced so I have a better idea of what kind of enzymatic activity could be taking place.

Since refining my process, which can certainly seem overly complex/critical/dorky, I am seeing attenuation in the ballpark of what I'd expect - most times. Sometimes I'm thrown a curveball that I try to figure out (dark, roasty beers), or a new-to-me yeast strain that I need to become familiar with, but it's all part of the fun of homebrewing for me.

You definitely need to account for the initial heat loss to the cooler and the grain bed.  When I use my coolers, I mash in (dough in?) about 10 degrees higher than I expect to be the stabilized temp.  I take the mash temp after stirring and making sure it's all stable.  Once it's stable, the losses are very low over an hour.
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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #12 on: December 17, 2015, 05:26:25 PM »
mash indoors or outsoors with that cooler? i've never done a mash outside in cold temps, but as far as indoors, mine holds within couple degrees over 60-75 minutes

I mash outdoors.  Even when temps are in the 20s, my cooler doesn't lose more than 2F.
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Offline Stevie

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does gradual heat loss in mash affect fermentability of wort?
« Reply #13 on: December 17, 2015, 05:29:31 PM »
mash indoors or outsoors with that cooler? i've never done a mash outside in cold temps, but as far as indoors, mine holds within couple degrees over 60-75 minutes

I mash outdoors.  Even when temps are in the 20s, my cooler doesn't lose more than 2F.
Same. The trick is to learn how high to heat your strike water to accommodate the cooler (or preheat), stir well, shut the lid, leave it alone.
« Last Edit: December 17, 2015, 05:32:15 PM by Steve in TX »

Offline heavydeadlifts

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Re: does gradual heat loss in mash affect fermentability of wort?
« Reply #14 on: December 17, 2015, 06:03:08 PM »

I mash in a red cooler.  Red coolers have it all over those pesky blue coolers.

My blue cooler would disagree
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