Skimming Out Barms: Is That A Legitimate Way To Lower Attenuation?

[Protos]

Gentlemen, I'm trying to recreate some historical top-fermented recipes that require unusually low levels of attenuation, like 20 to 40% AA. Originally, it was possible due to low-attenuating yeast strains which have long been lost, and also due to a special technique when a closed fermentation vessel was periodically tapped to partly extrude the yeast.

In a modern recommendation on how to achieve a similar effect it's suggested to constantly skim out the active barms as long as it regrows on top of the fermenting wort.

Before trying this method practically, I'd like to ask you: what do you think, is that theoretically possible at all, to drop the attenuation level by periodically removing part of actively fermenting yeast? I suspect it would just multiply and regrow again and again, however long it takes for the yeast to reach it's attenuation limit.

Or do I miss something?

 

[Kickass]

For the unfamiliar, what are barms?

 

[Sam_92]

I think that you are correct, skimming barms isn't going to lower attenuation. I think you would be better off starting with barley seed and malting it using old techniques like fire kilning.....

Maybe ask @bracconiere to make you some super under-attenuating malt.

 

[Protos]

For the unfamiliar, what are barms?

Sorry for talking obscure. Barms, if I correctly understand the term, is an English equivalent to the German word Kräusen, that is a frothy layer of actively fermenting yeast.

 

[Protos]

super under-attenuating malt

Yes, undermodified malt might be a part of the picture. However, I doubt it was greatly less modified than the modern Weyermann Floor Malted Bohemic, f.ex., as the recipes in question are from industrial Scandinavian breweries of the 19th-early 20th centuries, not the medieval ones. It seems, it's the yeast that was the key part. And it's been lost.

 

[Miraculix]

Modification does not really affect attenuation. The impact is on mash efficiency.

 

[madscientist451]

Gentlemen, I'm trying to recreate some historical top-fermented recipes that require unusually low levels of attenuation, like 20 to 40% AA.

Why not just mash high, say 160F to create an wort that is not fully fermentable, use whatever yeast you want, wouldn't that accomplish the same thing?

 

[Protos]

In other chewy recipes (which I like), I did several mashes in the 72-74C / 165F range and used the lowest attenuating yeast available, like S-33 and London ESB. Never managed to get lower than 65% AA, though.
It seems, the only options left are Pasteurizing or employing some yeast-killing agent. I've started a similar thread last autumn, where we'd come to the same conclusion, that mashing high and using low-attenuating commercial strains was still not enough to get lower than 60%.

This time I just wanted to consult about the Yeast-Skimming Technique, which was promised to get where I want, but seems doubtful to me. If it was a working method, any top-cropping would reduce attenuation of the "donor" brew, which is hardly the case.

 

[madscientist451]

Found some information about using higher mash temps for low ABV beers, but it seems like you could do the same thing with higher gravity beers.
They have a chart that shows a good range to be 180-186F?
https://www.btobeer.com/images/tech.../lallemand-bestpractices-low-alcohol-beer.pdf

 

[Miraculix]

You might want to start to try a wine yeast. Most of these (not all of them!) Really can only metabolize the shortest of the sugars. CBC one should be a good choice as this one is actually used for beers. I don't know if other wine yeasts might contribute winy esters.

 

[McMullan]

It’s possible skimming slows reaching FG, but alone I doubt it stops FG being reached. Wort fermentability is the main factor. Maybe some pasturisation once the target has been reached?

 

[Protos]

https://www.btobeer.com/images/tech.../lallemand-bestpractices-low-alcohol-beer.pdf

Wow, that looks like a great suggestion and an interesting experiment to try!
Now I'll study whatever info I could find on the web on super-hot-temp mashing.

UPD
Not much did I found. Mostly laments of unfortunate homebrewers who overheated their mashes.
Now I wonder, which enzymes are responsible for starch conversion for an hour at 80C / 180F and more, as suggested by Lallemand in the paper. The common knowledge is that all enzymes are extinguished after 20' above 76C. So, the resulting super-hot-mashed wort should come out not just low-fermentable, but starchy, eh? It seems there's no other way to find it out than to make an experimental nano-batch. What if it works?

 

[youngdh]

Lowering your mash pH well below ideal will stunt the amalyase enzymes.

 

[dmtaylor]

I recently brewed a Munich dunkel SMASH beer where I kilned or roasted my own pale malt in the oven for almost 2 hours. The finished beer was very dark and very tasty, but attenuation with two standard lager yeasts (S-189 and Diamond) was only like 55-60%. Conversion was definitely still happening, because within a few minutes, I could see the standard mash appearance where clear sugary liquid was separating from the grain bed, etc.

So, I think kilning might be the key here, keeping in mind that results may be variable and much experimentation might be required to get predictable results.

 

[Knox]

Hey @Protos
Limiting attentuation is always hard and will leave off-flavours if the fermentation gets stuck. If you want to hit a really low attentuation use a Maltotriose negative strain, have a low OG, a high strike temp and mash above the recommended range. This should promote a full fermentation, but low attentuation.

I do not know enough about malt to know if homekilning would work in this case. Could be a fun trial run to set up.

 

[Protos]

Thank you guys for your input!
@Knox, what is the higher mashing range you suggest, is that the 80-85°C as Lallemand suggests above? Will that work, what you think?

That's all for Danish recipes from the book by Wrisberg. Wanna try the Hvidtøl and light Skibsøl recipes from it.

 

[Miraculix]

Thank you guys for your input!
@Knox, what is the high fermentation range you suggest, is that the 80-85°C as Lallemand suggests above? Will that work, what you think?

That's all for Danish recipes from the book by Wrisberg. Wanna try the Hvidtøl and light Skibsøl recipes from it.

I think you meant F, didn't you?

 

[Protos]

No, I meant exactly Eighty-plus Degrees Celsius (82-86, to be precise). In Fahrenheit, that would be 180-187.
That's the mash range Lallemand suggests for very-low-alcohol Beers in the booklet linked above by madscientist451
I know that looks wild and I wonder which enzymes are expected to work in such a range, but it's a suggestion from Lallemand who probably know something I don't know.
Knox advice looks much like the Lallemand's: low OG, a high strike temp and mash above the recommended range. So, I'm asking him to elaborate which range he means. Is that the same super-hot 82-86 Celsius range that the Lallemand booklet suggests?

Here is the citation from the booklet:

Recommended low alcohol procedure
1 - Mash a well modified ale malt at an initial temperature between 82-86°C
(180-187°F).
2 - Target a low OG between 1.020 – 1.027 (5.1-6.8°P)
3 - Lauter as normal but ensure pH and gravity remain within normal brewing levels.
(5.1-5.4) Acid additions may be necessary.
4 - Boil as normal, again being careful to maintain normal pH levels. It is also possible
to add lactose at this stage to increase mouthfeel.
5 - Ferment using a maltotriose negative yeast strain such as LalBrew® Windsor and
LalBrew® London to lower the potential alcohol yield.

 

[Miraculix]

No, I meant exactly Eighty-plus Degrees Celsius (82-86, to be precise). In Fahrenheit, that would be 180-187.
That's the mash range Lallemand suggests for very-low-alcohol Beers in the booklet linked above by madscientist451
I know that looks wild and I wonder which enzymes are expected to work in such a range, but it's a suggestion from Lallemand who probably know something I don't know.
Knox advice looks much like the Lallemand's: low OG, a high strike temp and mash above the recommended range. So, I'm asking him to elaborate which range he means. Is that the same super-hot 82-86 Celsius range that the Lallemand booklet suggests?

Here is the citation from the booklet:

Ok, you wrote fermentation range, instead of mashing range. That confused me a bit.

 

[Protos]

Oh, my bad. Thank you for noticing! Fixed.

 

[Knox]

Thank you guys for your input!
@Knox, what is the higher mashing range you suggest, is that the 80-85°C as Lallemand suggests above? Will that work, what you think?

That's all for Danish recipes from the book by Wrisberg. Wanna try the Hvidtøl and light Skibsøl recipes from it.

I think Lallemand's recommendation is correct. It would limit the effectiveness of the enzymes and promote more dextrins.

As I mentioned before, I recommend starting with a low OG wort. Because if you try to make a higher gravity beer using this method you will still have plenty of fermentables in there to reach the +60% attentuation.

 

[Protos]

Thank you @Knox!
A theoretical question: which enzyme works at that hot temperature range of 80-85C?
Do we rely here on the trace activity of Alpha-Amylase?

That would ruin the common wisdom I've always held that Alpha-Amylase deactivates after 20 minutes at 76C, and that mashing above that point would produce not a low-fermentable wort but just an unconverted starch soup.

 

[dmtaylor]

Thank you @Knox!
A theoretical question: which enzyme works at that hot temperature range of 80-85C?
Do we rely here on the trace activity of Alpha-Amylase?

That would ruin the common wisdom I've always held that Alpha-Amylase deactivates after 20 minutes at 76C, and that mashing above that point would produce not a low-fermentable wort but just an unconverted starch soup.

I don't have exact figures, but I imagine some of the alpha amylase would remain active in that range for about 1-5 minutes. And whatever enzyme is able to survive would be working at warp speed until it all denatures. Mostly... yeah you'll likely have a starch soup.

But maybe knock that temperature back to closer to 73-75C and see what you can get there.

 

[Protos]

On a Danish brewing forum, I see that some people have actually used the 80-85C mash. They achieve FG in low thirties and are happy with the results, althogh noting that the beer comes out "floury" (=starchy). Very interesting experiment, worth trying.

At 75C I will get a standard attenuation, I know that well as I often employ 74C mash for some styles.

 

[Northern_Brewer]

CBC one should be a good choice as this one is actually used for beers. I don't know if other wine yeasts might contribute winy esters.

The main things to worry about with wine yeasts in beer are the fact that most of them are phenolic and most of them are killer strains so don't play nicely with beer yeasts. That's less of a factor for the situations in which CBC-1 is used. I had a go at identifying POF and killer status of wine yeasts in this thread, V1116 is one of the very few that is (relatively??) non-phenolic.

 

[Knox]

Thank you @Knox!
A theoretical question: which enzyme works at that hot temperature range of 80-85C?
Do we rely here on the trace activity of Alpha-Amylase?

That would ruin the common wisdom I've always held that Alpha-Amylase deactivates after 20 minutes at 76C, and that mashing above that point would produce not a low-fermentable wort but just an unconverted starch soup.

That is for people who knows way more then me in the matters of biochem. But an educated guess would be we are working with the trace acitivity of Alpha-Amy.
Remember that your grainbill is very small, so there aren't actually that many starches to convert. So 20 mins might be all you need tbh. The important bit here is to limit the beta amylase.

One reason for the recommended temp from white labs is because that mash temp of 80-85 is what a lot of craft breweries work from for making NABs or LABs. We often add glucose to the beer and pitch a yeast that cannot ferment maltose.

 

[Protos]

That makes sence and sounds quite logical. Indeed, as long as enzyme activity doesn't extinguish instantly and there's little starch to convert, quick conversion at 80-85 looks quite feasible. Now need to try that!
There's quite a few great historical recipes I've been long wanting to try, which require super-low attenuations from 30% to 50% - like Danziger Jopen and Mumme, and a supersweet Latvian dark Lager, and a vintage English ale from historical records, and now Danish beers from Wrisberg's book. I just like sweet and chewy beers. If I only master the low-attenuation technique, I'd make them all!

 

[Protos]

Today I brewed the beer in question, a 1913 Hvidtøl. Mashed it for an hour rising from 78 to 84 C, then boiled for an hour.
Got 80% mash efficiency and the weirdest wort I've ever produced: thick, murky and completely devoid of sweetness, 1.033 OG to fermenter.
Iodine test returned a mix of slightest purple hues with normal iodine rusty colour.
Inoculated the wort with the lowest attenuating yeast I have (2nd generation Mangrove Jack's M10 Workhorse) and now will wait what will happen.

 

[Miraculix]

Today I brewed the beer in question, a 1913 Hvidtøl. Mashed it for an hour rising from 78 to 84 C, then boiled for an hour.
Got 80% mash efficiency and the weirdest wort I've ever produced: thick, murky and completely devoid of sweetness, 1.033 OG to fermenter.
Iodine test returned a mix of slightest purple hues with normal iodine rusty colour.
Inoculated the wort with the lowest attenuating yeast I have (2nd generation Mangrove Jack's M10 Workhorse) and now will wait what will happen.

Devoid of sweetness is a good sign, you mainly got longer sugars in there, these don't taste sweet.

 

[Protos]

I believe, there's very little sugars in the solution, it tastes remarkably less sweet than a wort mashed at 72-74C.
I wonder, what then makes the solution so chewy, even at that thin SG. Must be starches, probably. Have no idea how they will impact the beer.

 

[madscientist451]

That's a pretty high mash temp, will be looking forward to hearing about how it turns out.

 

[Knox]

Got 80% mash efficiency and the weirdest wort I've ever produced: thick, murky and completely devoid of sweetness, 1.033 OG to fermenter.

The murky part sounds like a lot of starches were left in the finished wort. A way to getting them to floc is to simply boil some more. As for your lack of sweetness, what was your cold wort volume?

Because 1.033 in 5ls tastes very different from 1.033 in 20ls.

 

[DBhomebrew]

As for your lack of sweetness, what was your cold wort volume?

Because 1.033 in 5ls tastes very different from 1.033 in 20ls.

Huh?

 

[Knox]

Huh?

Sorry for not being clear.
Sweetness has a threshold before being detectable, I don't remember the total amount. But when I was taking my brewing course we had to taste to worts with the same gravity but made in various batch sizes. This was to illustrate that you can't simply scale a recipe 20x one or the other way, as the wort you will get will taste different from your reference. I found this exercise very useful, but it is probably more variable the larger you go in the business.

I hope that clears it out.

 

[DBhomebrew]

I hope that clears it out.

Not at all.

 

[bracconiere]

i'd do a seperate mash with flaked barley, maybe toasted though, with just alpha amylase added....mix em...just don't drink too much!

 

[bracconiere]

Huh?

i might be way off here, but it's like BMI? it depends how tall the fermenter is?

 

[Protos]

The murky part sounds like a lot of starches were left in the finished wort. A way to getting them to floc is to simply boil some more. As for your lack of sweetness, what was your cold wort volume?
Because 1.033 in 5ls tastes very different from 1.033 in 20ls.

The cold wort volume was 5 L, but I'm comparing its taste to the taste of worts of exactly the same gravity and volume - f. ex. a 5L batch of 1.033 Grätzer I brewed just recently, a 6L batch of 1.032 Grisette I made in autumn, or a 5L batch of 1.032 English Mild of the last spring. Being thin, they weren't particularly sweet either, but this one is significantly less sweet than those three worts.

Currently I'm somewhat concerned about that after a week in primary the beer still shows signs of active fermentation (the yeast is M10 Workhorse, a strain close to S-33). My other extra-low-gravity beers usualy calm down at the day 3 or 4. Knowing that this kind of low-gravity starchy wort is particularly succeptible to infection, I went nuclear with sanitation, using peroxyacetic solution. I don't dare to open and check gravity to not introduce airborne bugs.

 

[Knox]

The cold wort volume was 5 L, but I'm comparing its taste to the taste of worts of exactly the same gravity and volume - f. ex. a 5L batch of 1.033 Grätzer I brewed just recently, a 6L batch of 1.032 Grisette I made in autumn, or a 5L batch of 1.032 English Mild of the last spring. Being thin, they weren't particularly sweet either, but this one is significantly less sweet than those three worts.

Currently I'm somewhat concerned about that after a week in primary the beer still shows signs of active fermentation (the yeast is M10 Workhorse, a strain close to S-33). My other extra-low-gravity beers usualy calm down at the day 3 or 4. Knowing that this kind of low-gravity starchy wort is particularly succeptible to infection, I went nuclear with sanitation, using peroxyacetic solution. I don't dare to open and check gravity to not introduce airborne bugs.

I would give your fermenting wort a taste. See if some funky bugs decided to live in it and if the raw wort flavour has gone away. Because if it hasn't the yeasts are probably experiencing a hard time fermenting the wort as it stays very dense as they move around in it.

I wouldn't be too scared of infection tbh. If you at least had some isomerization from hops, lactic acid bacteria wont spoil it right away. The beer is producing carbon dioxide to protect it from acetic bacteria. So take a gravity reading, just stray your equipment with some alcohol sanitizer and you will be fine.

 

[Protos]

Thanks for encouragement! Well, I went to check the gravity.

From one side, the beer is fine: although it's a bit more tart than I'd enjoy, it definitely doesn't show signs of acetic or diastatic infection, which sometimes taint my brews. It has some hint of a flavour completely new to me, I'd call it "rustic", "wood-like" or "hay-like", it's not unpleasant and I think it's the flavour of unconverted starches (the beer is still murky and opaque).

From another side, I failed to get the desired attenuation of 30%: the gravity went down from 1.033 to 1.012, which gives a 2.75% Alc. content instead of 1.26% in the recipe and a pretty standard for this strain attenuation of 63%. With this yeast, I'd get same attenuation with mashing at 70C, so mashing at the super-high temp turned out to be pointless.

I decided to let it sit in the fermenter as long as it takes for the starches to settle, at least partly. Might transfer it to a secondary for a prolonged lagering, will see in a week.