Mash Time and Fermentability

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MEPNew2Brew

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Does the length of the mash affect fermentability, assuming the mash temperature is held constant through the entire mash? If so, why?
 

FirstAidBrewing

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Depending on the crush, it can add a few points. However, if you have a good crush there is no reason to mash longer. It's all about how efficiently you can convert your starches.
 

Gavin C

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Does the length of the mash affect fermentability, assuming the mash temperature is held constant through the entire mash? If so, why?
There are other players involved but fermentability is governed chiefly by the content of maltose and dextrine in the wort. The ratio between the two being important.

The higher the maltose to dextrin ratio the more highly fermentable the wort becomes.

Unfortunately for brewers this ratio is not governed by mash duration but by mash temperatures. Hence the emphasis in recipes placed on mash temps, whereas mash duration often seems to be somewhat arbitrary.

Nailing accurate temperatures is therefore key if the planned wort is to be produced.

It would be fair to mention though, that cooler mashes will typically take longer to reach full conversion than hotter mashes, (all other factors being equal). Most chemical reactions occur faster at higher temperatures and this is indeed the case for the enzyme-mediated chemical reactions involved in a mash.

The ratio of maltose: dextrin is temperature related and not tied to mash duration.

As to why? That is related to the different enzymes responsible for the production of the highly fermentable short chain simple sugars like maltose and the less fermentable longer chain dextrines.

More info here

From The Braukaiser. Mash pH and Mash temperature. effects on different enzymatic activity.

Hope that helps.
 

RM-MN

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Does the length of the mash affect fermentability, assuming the mash temperature is held constant through the entire mash? If so, why?
Assuming an adequate grain milling, longer mashes don't really affect the fermentability because the temperatures that activate the enzymes that produce the maltose and dextrine also destroy those same enzymes. That is the basis for choosing the mash temperature as the beta enzyme denatures quickly at the higher temperature so it cannot break down all the dextrines. Once denatured, it is done. It can't come back.
 

tsl346

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Yes, mash time does effect fermentability. You will convert starches to sugar relatively quickly but after that you will continue to convert non-fermentable sugar to fermentable sugars as they are further broken down. Example: at a 150 degree mash at the 30 min mark you will have about 8%ish starches left, 42% unfermentable sugar, and about 50% fermentable sugar. After 60 minutes your starches will be close to 0%, UFS at 16%, and FS at about 84%.
 

Gavin C

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@tsl346

None of this is correct to the best of my knowledge. I would be very interested to read your source for this information which is counter to everything else I have ever read on mash chemistry and kinetics.
 
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MEPNew2Brew

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Yes, mash time does effect fermentability. You will convert starches to sugar relatively quickly but after that you will continue to convert non-fermentable sugar to fermentable sugars as they are further broken down. Example: at a 150 degree mash at the 30 min mark you will have about 8%ish starches left, 42% unfermentable sugar, and about 50% fermentable sugar. After 60 minutes your starches will be close to 0%, UFS at 16%, and FS at about 84%.
Thanks for the responses folks.

Tsl346 - if you have additional info, or further explanation, that would would be appreciated.
 

ol-hazza

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My fun fact on this subject is that even within preferred mash temp ranges enzymes will denature within a matter of hours.

From an article in BYO

In some cases, enzymes will actually denature within their stated range. For example, at 149 °F (65 °C), beta-amylase is denatured within 40–60 minutes and alpha-amylase activity will cease after 2 hours at 153 °F (67 °C). The point is that, by changing mash temperatures, you are not cleanly switching enzymes on and off. Due to their simple mechanism of action, your control over them is much more “squishy.” BYO source
 

tsl346

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http://www.woodlandbrew.com/2013/01/mash-temperature-theory.html

It is from the charts found on this page (hopefully the picture loads correctly)

And this does make sense to me since at most mash temps there are both alpha and beta amalyse active so if you are producing unfermentable sugar at higher temps that those unfermentable sugars can be broken down further into fermentable sugars.

150 mash.PNG
 

Gavin C

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http://www.woodlandbrew.com/2013/01/mash-temperature-theory.html

It is from the charts found on this page (hopefully the picture loads correctly)

And this does make sense to me since at most mash temps there are both alpha and beta amalyse active so if you are producing unfermentable sugar at higher temps that those unfermentable sugars can be broken down further into fermentable sugars.
Thanks for sharing that graph.

I don't interpret it the same way as you are. I don't agree with your interpretation.

Yes fermentability is increasing over the course of the mash but that is because the sugar content is increasing as the starch content is reducing. You can't use this to control fermentability except by not achieving full starch conversion.

At the earlier phase in the mash duration, unfermentable sugars are present in greater proportion yes. These longer sugars are not reducing in quantity but are only reducing as a percentage of the total sugar content as more and more starches are converted to maltose.

Concurrent with the reducing percentage of dextrine we see an increasing percentage and increasing quantity of maltose.

It is the increasing maltose in the mash that causes the reducing percentage of dextrine simply as a result of increasing sugar content.

Dextrines are not being converted to maltose, starches are, that's why the percentage of dextrine is reducing.

In all mashes full starch conversion is a universal goal, intentionally leaving starches in the wort to reduce fermentability is not desirable and not applicable to the actual controlling of fermentability. Brewing models typically assume a mash with near ~100% conversion.

Thanks again for the link and graph

The other two graphs in the article however show the full picture where mash temperature is the key player, not mash time. The link you shared does not support your position. EDIT: It DOES

Hotter Mash more UFS


Cooler Mash less UFS



Brulosopher did a recent test of differing mash temps. A less fermentable wort was indeed produced with hotter mash temps.

http://brulosophy.com/2015/10/12/the-mash-high-vs-low-temperature-exbeeriment-results/

This image shows the FG of the hot and cool mash. Cool 1.005 Hot 1.014


Image from the @brulosopher 's website
 
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tsl346

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Thanks for sharing that graph.

I don't interpret it the same way as you are. I don't agree with your interpretation.

Yes fermentability is increasing over the course of the mash but that is because the sugar content is increasing as the starch content is reducing. You can't use this to control fermentability except by not achieving full starch conversion.

At the earlier phase in the mash duration, unfermentable sugars are present in greater proportion yes. These longer sugars are not reducing in quantity but are only reducing as a percentage of the total sugar content as more and more starches are converted to maltose.

The other two graphs in the article however show the full picture where mash temperature is the key player, not mash time. The link you shared does not support your position.
Mash temperature is definitely a huge player in fermentabilty and I agree that the charts show this, I was not trying to say otherwise. I agree that I do believe that mash temp is the main player.

But, I also believe the charts show that the longer you mash it will produce more fermentable sugars. From your interpretation of the graph I would think that the FS and UFS %'s would need to add up to 100% as the starch content changes (correct me if i'm understanding you wrong). From the graph itself, the starch, FS, and UFS always add up to 100%, so my interpretation is that it is showing the % of starch, UFS, and FS of the total starting mass of starch.

With this interpretation, the 160 degree temp chart. At 30 minutes the total starch is about 3%ish meaning that the total sugar content (FS + UFS) is about 97%. Over the next 30 minutes it shows the starches decreasing to roughly 0%, a difference of about 3%, but it shows the UFS and FS changing significantly more that 3%. So that says that the UFS is being broken down into FS.
 

Gavin C

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With this interpretation, the 160 degree temp chart. At 30 minutes the total starch is about 3%ish meaning that the total sugar content (FS + UFS) is about 97%. Over the next 30 minutes it shows the starches decreasing to roughly 0%, a difference of about 3%, but it shows the UFS and FS changing significantly more that 3%. So that says that the UFS is being broken down into FS.
I agree with you there but would argue the graph is in error, [EDT: THE GRAPH IS NOT IN ERROR, I AM ]not the science. Specifically the point of intersection of the red and green on the y axis and the starch curve leveling off too early. These are only models after all and not actual measurements taken on specific mashes. They should not be interpreted with the level of exactitude you are using IMO.

The other interpretation is that the dextrin is being converted to maltose by the action of alpha amylase. Not something I am familiar with but concede I have much to learn on this specific topic.
 
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Magnus314

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Yes, definitely. Provided you haven't mashed SO high you've denatured all the Beta Amylase before the mash cools off a bit, or you aren't artificially keeping the mash temps high (in the Alpha range).

I do a looooong mash for a lowcarb light lager. Usually 2 hours+, starting at 150*. It ferments out at 1.000, and finishes at about 148*.

If I go 4 hours in the mash it ferments out to 0.998 or even lower, with the same starting temp. It also finishes at about 144*.

The SAME malt bill at 150* for 1 hour ferments to a 1.006 FG with a final temp of 149*.
 

tsl346

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I agree with you there but would argue the graph is in error, not the science. Specifically the point of intersection of the red and green on the y axis and the starch curve leveling off too early. These are only models after all and not actual measurements taken on specific mashes. They should not be interpreted with the level of exactitude you are using IMO.

The other interpretation is that the dextrin is being converted to maltose by the action of alpha amylase. Not something I am familiar with but concede I have much to learn on this specific topic.
Fair point. I need to start brewing enough to be able to actually do this type of experiment.
 

Gavin C

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Fair point. I need to start brewing enough to be able to actually do this type of experiment.
Been thinking more about this and I've come to the conclusion that I'm completely wrong. I thing your interpretation is completely right. The non-fermentable sugars being repeatedly cleaved into simpler fermentable sugars by alpha and/or beta amylase still present and not as yet denatured.

This would explain why fly-spargers mash-out
 
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