mash temperature vs mash time

[odie]

I mash for several hours. like 10 hours most times. I do this since I set my BIAB to mash while I'm sleeping or at work so that my actual brew day is shorter.

Granted, most conversion occurs withing the first 20-30 minutes.

So I mash at 150' for 10 hours. I'm quite sure I've hit 100% conversion. Perhaps my wort is "over-fermentable"? I do wonder if my beers might be a little thin on the "mouth feel". Some beers are supposed to have residual unfermentable sugars or starches?

Would raising the mash temps to say 155 or even 160 result in a more "normal" wort after 10 hours? Would the enzymes denature enough to have a more "normal" conversion rate?

Or is 10 hours at any mash temperature range going to allow either the alpha or beta to convert everything?

 

[doug293cz]

A 10 hour mash is going to convert pretty much all of the starch to fermentable sugars and alpha limit dextrins. An alpha limit dextrin is a remnant of a branch point from amylopectin (the branched form of starch.) They consist of three short glucose unit chains (2 - 4 glucose units each) with an alpha 1-6 bond forming the branch near the center (the bonds that form the linear chains in starch are alpha 1-4 bonds.) In limit dextrins, the linear portions of the chains are too short for either alpha or beta amylase to hydrolyze (break) them.

There is a third enzyme in barley malt that is important for starch hydrolysis that is often ignored. This enzyme is limit dextrinase, and it can hydrolyze the alpha 1-6 bonds that form the branch points in amylopectin and dextrins. The more action this enzyme has in the mash, the less limit dextrin you will have in the wort after the alpha and beta amylase have done all that they possibly can, and the more fermentable the wort will be, since dextrins are not fermentable.

The optimal temperature range for limit dextrinase is slightly below the optimal range for beta amylase. A case can be made that it is actually limit dextrinase, not beta amylase, that is responsible for the higher fermentability of wort mashed at low temperatures, or step mashed with a "beta" rest.

With that as background, mashing at higher temperatures for extended mash times will reduce the action by limit dextrinase, resulting in more limit dextrin in the final wort and decreasing its fermentability. So yes, mashing at higher initial temperatures for 10 hours should produce a less fermentable wort than mashing at lower temperatures for the same amount of time.

In a shorter mash (the typical ~1 hour), gelatinization of all of the grits may not be completed, so the alpha and beta amylase and limit dextrinase, cannot hydrolyze all of the hydrolyzable starch, resulting in more dextrin (not all limit dextrin) than you would have remaining in a wort from an extended mash, done at the same temperature, that achieved 100% gelatinization of all grits.

You will need to experiment with different mash temps to determine what gives you the fermentability you want with your extended mash times. You may find you need to add special malts that are less hydrolyzable (eg. carapils), or maltodextrin, to achieve your goals.

Brew on

 

[odie]

hmmm

well, I mash in at ambient and take a shower. 30 minutes later the mash is at 150 (or whatever I set it at). At that point, raising the temps to 155 or 160 might be irrelevant.

 

[doug293cz]

hmmm

well, I mash in at ambient and take a shower. 30 minutes later the mash is at 150 (or whatever I set it at). At that point, raising the temps to 155 or 160 might be irrelevant.

If your water starts at 70°F, then 30 minutes to 150°F is a heating rate of 2.67°F/minute, so you would only spend 10 / 2.67 = 3.75 minutes going from 140°F - 150°F. That doesn't seem like enough time to get much limit dextrinase action. If you just set your target mash temp to 156° you might see a noticeable difference in fermentability.

Brew on

 

[VikeMan]

I agree with what @doug293cz said in #2 and #4. I also think it's unlikely that anyone will be able to provide empirical data for this scenario (10 hour mashes at various temps). Looks like it's time to experiment.

 

[mac_1103]

Can limit dextrinase even act on those linkages before the alpha and beta amylases have done their jobs, or is it sterically inhibited from accessing the branch points of longer chain starches?

 

[tracer bullet]

On a related note, if one were to intentionally make a mash as fermentable as possible, do they start at the higher temp and gradually work downwards? Something about beta / alpha / long / short "chains"?

I'd be working on the assumption for OP Odie that going from cold to high and holding high for a while might not be super fermentable if that were the goal.

I'm not trying to reach a conclusion but if one were to minimize the work involved they could perhaps start cold and head high if they were making a stout and start high and let cool if they were making a beer where minimum body was desired.

 

[doug293cz]

Can limit dextrinase even act on those linkages before the alpha and beta amylases have done their jobs, or is it sterically inhibited from accessing the branch points of longer chain starches?

I rather doubt it is sterically inhibited, since it is a less thermally stable enzyme. If it had to wait for significant alpha amylase action before it could work, then it would likely be mostly denatured before it could even start. Beta amylase isn't going to do much to expose the branch junctions, since it just "nibbles" on the ends of starch chains, and isn't very effective at reducing the length of long chains, unlike alpha which can break 1-4 bonds at random points.

Brew on

 

[doug293cz]

On a related note, if one were to intentionally make a mash as fermentable as possible, do they start at the higher temp and gradually work downwards? Something about beta / alpha / long / short "chains"?

I'd be working on the assumption for OP Odie that going from cold to high and holding high for a while might not be super fermentable if that were the goal.

I'm not trying to reach a conclusion but if one were to minimize the work involved they could perhaps start cold and head high if they were making a stout and start high and let cool if they were making a beer where minimum body was desired.

No, just the opposite is true. To maximize fermentability, you want to maximize the action of limit dextrinase, in order to reduce the amount of limit dextrin in the final wort. Less dextrin => higher fermentability.

If you start high, you will denature most of the limit dextrinase early in the mash, and there will be none left to work on the starch that doesn't get gelatinized until later in the mash.

I'm going to say something that most people here will find very controversial: We don't need beta amylase at all to create a maximally fermentable wort. Alpha amylase and limit dextrinase together can achieve maximum wort fermentability. Beta is simply useful for producing only maltose, and no other starch fragments, monosaccharides, or trisaccharides.

Alpha works like a food processor chopping up kale. They both chop bigger things into smaller things at random locations on the bigger things. So, early in the process, you are creating a lot of relatively large pieces. But, as you continue, the pieces keep getting chopped smaller and smaller, until you reach a size limit. With alpha amylase, that size limit is monosaccharides (glucose/dextrose), disaccharides (maltose mostly), and limit dextrin.

Brew on

 

[tracer bullet]

OK, interesting!

I've always read that lower mash temps ("better" for beta) tend to give lower final gravities and higher mash temps ("better" for alpha) tend to give higher final gravities. I think I've seen it for myself, and I just looked to verify some Brulosophy experiments showing it to be the case as well, the lower mash temps gave lower final gravities.

But to maximize fermentability, one would ramp up the temperatures, not down? I'm quite sure that's what you are saying, it's just the opposite of what I'd always believed.

And you're saying that a higher temp can in fact give a lower final gravity? Or maybe you didn't say that exactly, you said maximum fermentability but to me they are the same.

I'm quite intrigued by this, you do know more than I do it's just counter to some of what I've read or misinterpreted or believed.

I think it's still on topic...

 

[mac_1103]

I'm going to say something that most people here will find very controversial: We don't need beta amylase at all to create a maximally fermentable wort.

Why would fundamental biochemistry / enzymology be controversial?

 

[mac_1103]

To maximize fermentability, you want to maximize the action of limit dextrinase, in order to reduce the amount of limit dextrin in the final wort. Less dextrin => higher fermentability.

So does this sort of get back to odie's original question? If he was doing his long mash at an even lower temperature then might we expect him to wind up with a thinner beer?

 

[CascadesBrewer]

And you're saying that a higher temp can in fact give a lower final gravity? Or maybe you didn't say that exactly, you said maximum fermentability but to me they are the same.

Interesting discussion. I think there needs to be a combination of both high mash temperature and a rather long mash to give the Alpha amylase time to do its random chopping to create lots of small chain sugars. But how long does that mash have to be?

I recall some data from Kai Troester that showed around a 149F single infusion mash created the highest fermentability wort (in a 60 minute mash?). This seemed to be a good range where Beta amylase stayed active for a decent period, and Alpha amylase was also active. I often see step mashes using one step in the mid to low 140's and another in the mid to upper 150's. My understanding is that this will create a more fermentable wort than just a single infusion. I pretty much just do single infusion mashing myself. I tend to mash for 60-90 at 149F for higher fermentability, and 60 minutes at mid-150's for less fermentability.

I feel like I need a better understanding of the role that limit dextrinase plays.

 

[doug293cz]

And you're saying that a higher temp can in fact give a lower final gravity? Or maybe you didn't say that exactly, you said maximum fermentability but to me they are the same.

No, I did not say that a mash that starts initially at a higher temperature can have a higher fermentability. You need to start lower, at a temp where limit dextrinase has a relatively long (relative to total mash time) lifetime in order to maximize fermentability.

Yes, maximum fermentability corresponds to minimum FG.

Brew on

 

[Bassman2003]

OK, interesting!

I've always read that lower mash temps ("better" for beta) tend to give lower final gravities and higher mash temps ("better" for alpha) tend to give higher final gravities. I think I've seen it for myself, and I just looked to verify some Brulosophy experiments showing it to be the case as well, the lower mash temps gave lower final gravities.

But to maximize fermentability, one would ramp up the temperatures, not down? I'm quite sure that's what you are saying, it's just the opposite of what I'd always believed.

And you're saying that a higher temp can in fact give a lower final gravity? Or maybe you didn't say that exactly, you said maximum fermentability but to me they are the same.

I'm quite intrigued by this, you do know more than I do it's just counter to some of what I've read or misinterpreted or believed.

I think it's still on topic...

One always needs to factor in time with mash enzymes. Starting with beta then moving to alpha is the most efficient mash schedule with regards to time. Shortest possible to achieve the goal to be exact. An Alpha only mash will get the job done, it just needs a lot more time. I have never done a long mash like the OP, but the literature a wary of extending mash times any longer than necessary. Pro breweries are restrained by profits.

If you just rest at 158F, the most of the beta enzymes will be toasted and not get any work done. So Alpha has to do all of the work which takes a lot longer. The opposite is not as true because if you stay at 144F, Alpha will not denatured because the temp is lower than its optimal range. So it will be working some, but at a slow rate. Hope this helps and does not confuse.

 

[VikeMan]

If you just rest at 158F, the most of the beta enzymes will be toasted and not get any work done.

They'll get some work done. But they will denature much faster than at "beta rest" temperatures.

The opposite is not as true because if you stay at 144F, Alpha will not denatured because the temp is lower than its optimal range. So it will be working some, but at a slow rate.

Alpha will denature at 144F. But it will denature much more slowly than at "alpha rest" temps.

Often people discuss enzymes in the following form: "Enzyme "X" works between the temperatures of "Y" and "Z." Below Y, it's inactive. Above Z, it denatures."

For the amylase and limit dextrinase enzymes, this can useful, but also misleading. They all work over a wide range of mash temps (even at "protein rest" temps and "mashout" temps at the extremes). They all work faster at higher temps and slower at lower temps. They all denature faster at higher temps and slower at lower temps. (pH matters too, but that's another topic.)

But they also work at different rates (from each other) at any given temp and denature at different rates (from each other) at any given temp. So each has its own characteristic "optimal" or "most efficient" temperature, where most efficient means the temp where the most work could be done (assuming unlimited substrate and assuming the enzyme is working alone) before that enzyme is fully denatured.

Because the "most efficient" temperature for each enzyme is (individually) different, and/but because they to an extent work in tandem, further breaking down each other’s products more than they could have done alone, various single infusion temps and step mash strategies result in different fermentabilities and sugar/dextrin profiles.

 

[mac_1103]

Often people discuss enzymes in the following form: "Enzyme "X" works between the temperatures of "Y" and "Z." Below Y, it's inactive. Above Z, it denatures."

For the amylase and limit dextrinase enzymes, this can useful, but also misleading. They all work over a wide range of mash temps (even at "protein rest" temps and "mashout" temps at the extremes). They all work faster at higher temps and slower at lower temps. They all denature faster at higher temps and slower at lower temps.

Yeah. It seems like we sometimes forget that these enzymes don't exist to make wort and that "in real life" as it were, they do their jobs without ever spending any time in their optimal temperature range.

 

[Bassman2003]

The word denature is kind of difficult. From you post, it seems any temperature and exposure to water will "denature" the enzymes. Just at different rates. I think of denaturing as putting something above a threshold and it breaks down. In this case the threshold being water. But exposure is part of the equation too. Do the enzymes start denaturing in air after the crush and before the mash even starts?

Logically or real-world, if one did a 10 hour mash at 122F, the Alpha enzymes would probably hang around for quite some time. All the while not getting much work done either. So it is wise to utilize the enzymes at their optimum. I would like to see a comparison of a 10 hour mash and a normal mash when both were targeting the same outcome. It would shed some light on how these entities go about their business.

 

[mac_1103]

I don't think it's likely that a ten hour mash at 150F is really a ten hour mash. Either everything is converted before the ten hours are up or all the enzymes are denatured before the ten hours are up. Or maybe both.

 

[odie]

well...I've always read that at higher temps the enzymes will eventually "denature" and they are done converting starch to fermentable sugars. So if you mash in high, the enzymes will "burnout" before complete conversion, resulting in a beer with residual unfermentable sugars/starches giving in more "body" or higher FG.

I just figured at 150' for 10 hours I might be "over mashing" for certain styles.

I just did an english pub ale yesterday. So I tried 155' set point. Maybe I should have tried 160 or 165? I mashed in around 70-75 which was ambient Texas dawn. By the time I showered and left it had hit 155', about 30-40 minutes. It then ran all day at 155.

 

[odie]

I don't think it's likely that a ten hour mash at 150F is really a ten hour mash. Either everything is converted before the ten hours are up or all the enzymes are denatured before the ten hours are up. Or maybe both.

The entire mash is probably completely done in an hour or so. Nothing left to convert. It's just I will not get back to it until 10 hours later. So my electric kettle and recirc holds everything at 150 or whatever until I return for mashout & boil.

 

[mac_1103]

You might find this interesting. Even if it is 24 years old. Is linking PDFs not allowed? Or is it the source? Who knows? Anyway...

A New Approach to Limit Dextrinase and its Role in Mashing
Stenholm, K. and S. Home
Journal of The Institute of Brewing
105: 205-210, 1999

 

[RM-MN]

The entire mash is probably completely done in an hour or so.

You might be surprised at what time conversion takes. It doesn't take an hour but gelatinizing the starch from bigger grain particles might and conversion can't start until the starch is gelatinized.

 

[CascadesBrewer]

You might find this interesting. Even if it is 24 years old. Is linking PDFs not allowed? Or is it the source? Who knows? Anyway...

Not sure, but you can click through to the PDF here:
https://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1999.tb00020.x
I have not read the paper but this part of the summary does sound interesting: "Wort fermentability was more strongly correlated to the free limit dextrinase activity of malt than to the α- and β-amylase activities."

 

[doug293cz]

You might find this interesting. Even if it is 24 years old. Is linking PDFs not allowed? Or is it the source? Who knows? Anyway...

A New Approach to Limit Dextrinase and its Role in Mashing
Stenholm, K. and S. Home
Journal of The Institute of Brewing
105: 205-210, 1999

Not sure, but you can click through to the PDF here:
https://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1999.tb00020.x
I have not read the paper but this part of the summary does sound interesting: "Wort fermentability was more strongly correlated to the free limit dextrinase activity of malt than to the α- and β-amylase activities."

I've attached the paper below, and here's the absract:

Brew on

 

[mac_1103]

I've attached the paper below, and here's the absract:

Well geez, I could have done that.
Still trying to learn the rules around here.

 

[doug293cz]

Well geez, I could have done that.
Still trying to learn the rules around here.

IIRC, the ability to attach .pdfs to posts is a relatively recent change.

Brew on

 

[Bassman2003]

Thanks for the link. I read the paper and it is pretty interesting. Basically, include/start at a 62.5C (144F) rest if you want maximum fermentability. I have done this rest many times and found the beers to attenuate well. Now I know why.

 

[troxerX]

On another topic separate from conversion and enzymes, are there any concerns of excessive extraction of tannins from the grain husks as a result of such extended mash duration?, @odie have you experienced any excessive bitterness or astringency in your brews?, not sure what are the exact mechanisms for tannin extraction but curious if mashing that long will have an impact on that matter..

 

[odie]

I have not noticed any "tannin" issues. but then again, without a side by side tasting with a known "tannin" beer....well I just wouldn't know. I've never really even heard of "tannins" until people here started posting about BIAB squeezing and getting nasty "tannins". What is a "tannin" in respect to beer?

My buddies have no issues drinking my swill.

 

[VikeMan]

What is a "tannin" in respect to beer?

Tannins are polyphenols that come from grain husks and from hops. In the mash, the higher the temperature, the more tannins are extracted. And the higher the mash pH, the more tannins are extracted. Every beer contains tannins. Beer wouldn't taste like beer without them.

Whenever people talk about having tannins in their beer, they are usually talking about "excessive" tannins, causing noticeable, unwanted astringency.