How effecting attenuation affects flavor

[menschmaschine]

Most of my beers have mediocre attenuation. They usually get to the upper end of the applicable style. I chalk most of it up to aeration technique (shaking), but until I get an oxygen aeration kit and/or do a fast ferment test, I won't know for sure. I've played with mash temps and have tried various yeasts/pitching rates and fermentation temps, but the attenuation still seems to be consistently mediocre.

I'm not complaining about this, per se, but I am curious how compensating with the parameters that affect attenuation would affect the flavor of the final beer. For instance, if I had a lager attenuate to 1.014 (for simplicity's sake, single-infusion mashed at 153°F and "shaken"-aerated), it would have some level of body/sweetness related to that FG. How would this be different (in flavor/body/sweetness) if, for example, I mashed at 156°F and used pure oxygen for aeration and got the same attenuation? (Assume same OG's in both.)

Or, conversely, I (hypothetically) had an ale mashed at 149°F and "shaken"-aerated attenuate to 1.010. How would this differ in flavor from the same recipe, mashed at 154°F and aerated with pure oxygen, that attenuated to the same FG of 1.010?

Of course, I'm making the assumption here that aerating with pure oxygen causes an increase in attenuation. But my question is more... how does manipulating mash temperatures affect flavor vs. manipulating other factors that affect attenuation (all other factors being equal)?

 

[Evan!]

Manipulating mash temps and your grain bill, IMHO, are the best ways to adjust attenuation. Oxygenation, well, there's really no good way to create a controllable set here. I've oxygenated wort for 90 seconds with pure O2, and had piss-poor attenuation...but when I was making my Lambic, I purposely mashed high, didn't oxygenate or aerate at all, fermented at 60f (with non-rehydrated S-05), and it still finished at 1.010. So, really, I can't give you a 100% answer, but suffice to say that the best way of adjusting your level of residual sugar is to adjust the mash temp and the grain bill (add more crystal malts, etc., for lower attenuation). Other factors that have a big effect, though, are pitching rates and fermentation temps / temp swings, as you probably know. These are much more easy to get constant---in other words, it's better to keep your pitching rates the same, and adjust your mash schedule and/or grain bill, rather than the other way around.

JZ says that sometimes, for example with Belgians, when he wants to showcase that estery quality, he'll go low on the oxygen...but I'm leery of that...especially if you're bottling. My reasoning here is that when you adjust your mash temp and/or grain bill, you're actually affecting the ratio of fermentable/unfermentable sugars in the wort, so your maximum attenuation with any given yeast strain should be tied to that. But when you mess with the oxygen, you run the risk of leaving behind fermentable sugars...which, as everyone knows, can result in bottle bombs or foamy kegs. Me, I'd rather maximize the potential of my yeast, and just feed them more or less fermentable sugars in order to adjust my sweetness levels.

 

[menschmaschine]

It's good to hear that using pure O2 doesn't necessarily increase attenuation over a good shake. Grain bill is a good point, but I've messed with that as well. For example, I brewed a few batches of Helles that had Cara-pils. Once, I left out the Cara-pils altogether... same attenuation (borderline high for the style). Also, in my Helles brewing, I've lowered the dextrin rest (decocted up to) from 158°F to 156°F to 154°F... no apparent difference in attenuation.

I feel like my brewhouse attenuation is limited for some reason. Based on what I've seen in the past almost 2 years, if I ever wanted to brew a 1.008 beer, I'd have a tough time getting that low. I don't feel like I have room to play with parameters that affect attenuation because no matter what I try, there seems to be a bottom limit. Yet the residual sugars always seem to be unfermentable because I've never had over-carbonated beer.

Could a direct-fired mash-out cause an increase in unfermentable sugars (I do them every time)? I raise the temp to 168°F in about 5-10 minutes. Are there minerals necessary for yeast I'm not aware of? My water is extremely low in minerals, but I always add a little gypsum to the boil plus the grain itself adds plenty of nutrients and minerals. Or perhaps better, are there specific minerals supportive for beta-amylase enzymes I'm not aware of? I've never added minerals to the mash (water pH = 5.7).

 

[Piotr]

From my experience: I did recently 2 german lagers, they attenuated to 1.006 i 1.008. I mashed for 2 1/2 hours in 62-64*C.
Plus one Saison (1.007), this one I mashed 1 1/2 h in 64-65*C. In both cases I didn't do any mash-out.

About main question: taste of a 1.010 attenuated beer, one mashed low, one under-attenuated. I think the latter will be sweeter, because it has bigger percentage of simple sugars left, and they are far more sweet than dextrines. Think about tripel: dry, yet sweet...

 

[Evan!]

Well, I didn't say that pure O2 isn't an improvement---it certainly was in my experience, but again, there have been exceptions, so nothing is absolute. On the whole, though, I have had less stuck batches since going to O2.

Sounds to me like you're mashing too high if you want to get lower FG. 154f is pretty high if you want a dry beer. The lowest I've gotten a beer to go was 1.007, down from 1.074. It was a biere de garde, and it was mashed at 147f for nearly 2 hours. The lower you go, the more fermentable your wort will be, but you also need to mash longer to make sure full conversion happens. It's a trade-off. Also, when I am looking for a really fermentable wort, I often add simple sugars (table sugar, for instance) to the boil. If you added some sucrose and mashed at 148, I am guessing you could get down to 1.008.

I don't know if it's really a matter of minerals in your beer affecting conversion, but have you ever done an iodine test to see if you have reached full conversion? If not, I would start doing that. I don't see how a direct-fired mash could cause this, though, unless you aren't stirring very well whilst applying heat, which can result in hot pockets of wort in your mash, which can deactivate the enzymes fairly quickly, or simply raise the mash temp in various spots in the mash up to the mid to upper 150's, resulting in more LCD's. As long as you're stirring constantly, and applying low heat, I don't see that as an issue. But I would try going below 150f and see what happens.

 

[menschmaschine]

I've never done an iodine test, however, my efficiency is very high... ranges from 88-93%. So, as far as full-conversion goes... I guess I just assume. Or am I missing something there?... i.e., can unfermentable sugars get broken down to fermentable sugars with longer mash times at specific temps? (If so, this still wouldn't make a difference in the iodine test, right?) For instance, in a mash at 150°F both alpha and beta amylase enzymes are converting starches to sugar, with beta being favored. If left for a longer timeframe, would some unfermentable sugars produced by the alpha enzymes get further broken down to fermentable sugars by the beta enzymes, therefore increasing the proportion of fermentable sugars?

I use sugar in some beers, primarily Lyle's Golden Syrup in British beers. I actually try to keep my mash temps fairly low because of my mediocre attenuation. When I mentioned mashing at 154°F, that was after a rest at 135°F, which serves as a combo protein/saccharification rest. This was adjusted from Noonan's recommendation (for malts of a specific SNR) to mash at 131°F and decoct to 158°F.

I guess what I'm saying is that my attenuation seems to be slightly lower than most other brewers. Take Orfy's hobgoblin for example. He calls for a mash of 156°F for 90 min. with an OG of 1.056 and uses Nottingham yeast. To compensate for my attenuation "problem", I mashed at 153°F for 90 min.. My OG was 1.059 (this was one of those 93% efficiency days when I expected 88%) which I watered down to 1.056. After 7 days in the fermenter (fermentation appeared finished), it was 1.015. He gets 1.013. What gives?

 

[Evan!]

I've never done an iodine test, however, my efficiency is very high... ranges from 88-93%. So, as far as full-conversion goes... I guess I just assume. Or am I missing something there?... i.e., can unfermentable sugars get broken down to fermentable sugars with longer mash times at specific temps? (If so, this still wouldn't make a difference in the iodine test, right?) For instance, in a mash at 150°F both alpha and beta amylase enzymes are converting starches to sugar, with beta being favored. If left for a longer timeframe, would some unfermentable sugars produced by the alpha enzymes get further broken down to fermentable sugars by the beta enzymes, therefore increasing the proportion of fermentable sugars?

I use sugar in some beers, primarily Lyle's Golden Syrup in British beers. I actually try to keep my mash temps fairly low because of my mediocre attenuation. When I mentioned mashing at 154°F, that was after a rest at 135°F, which serves as a combo protein/saccharification rest. This was adjusted from Noonan's recommendation (for malts of a specific SNR) to mash at 131°F and decoct to 158°F.

I guess what I'm saying is that my attenuation seems to be slightly lower than most other brewers. Take Orfy's hobgoblin for example. He calls for a mash of 156°F for 90 min. with an OG of 1.056 and uses Nottingham yeast. To compensate for my attenuation "problem", I mashed at 153°F for 90 min.. My OG was 1.059 (this was one of those 93% efficiency days when I expected 88%) which I watered down to 1.056. After 7 days in the fermenter (fermentation appeared finished), it was 1.015. He gets 1.013. What gives?

I've never seen too many folks get matching FG's down to the 0.001 with any consistency. I wouldn't be concerned with a couple points here and there. Maybe he had more viable yeast that went further. Maybe he oxygenated more. Maybe one of your thermometers is off. Maybe the moon was aligned with jupiter that day. Who knows. But if it's a couple points off, I wouldn't worry a whole lot. I know, you say it's consistently a bit higher, to which I say, check your thermometer, go with pure O2 oxygenation, and make sure you have a big healthy cache of yeast per JZ's yeast pitching rate calculator. Past that, there's nothing I can think of, if the grain bills are the same.

I guess you could get some 5.2 buffer and see if that makes a difference, but I don't see how that'd affect attenuation.

 

[944play]

Your ferments might have a zinc deficiency. Apparently Zn does not stick around in the boil very well. ISTR one podcast describing a brewery that got rid of a galvanized ladder in their boil kettle and attenuation went down... but I can't remember if it was Palmer, JZ, or Graham Sanders.

You might employ a general purpose yeast nutrient. I use Wyeast's.

 

[enderwig]

I'm gonna ask the super simple question.

Are you positive of your thermometers calibration in the 140-170 range?

 

[menschmaschine]

Your ferments might have a zinc deficiency. Apparently Zn does not stick around in the boil very well. ISTR one podcast describing a brewery that got rid of a galvanized ladder in their boil kettle and attenuation went down... but I can't remember if it was Palmer, JZ, or Graham Sanders.

You might employ a general purpose yeast nutrient. I use Wyeast's.

That's an interesting point. My water is so low in minerals that I have my suspicions.

Are you positive of your thermometers calibration in the 140-170 range?

Yes, I'm sure my thermometer is calibrated and accurate.

 

[remilard]

I think you should try a forced fermentation. See if it is the wort or the fermentation.

 

[fixie]

Sweet Thread. I have been having some trouble as well. A recent I.P.A. I brewed OG 1.063 only fermented down to 1.026 I have no idea what to do with it. I tried it from the fermenter and it was soo sweet not what I was going for.

 

[dontman]

To be honest I feel that you are attributing more affect to oxygenation than is warranted.

In direct contrast to your situation, I tend to end up on the low end of the FG continuum and I just don't worry too much about aeration. Yes I shake the carboy for a minute or so. But nothing more.

I focus on enzyme activity. This is what I feel has the most profound effect on FG. Those long strand sugars show up as fully converted but they do not ferment. And since I make big beers for the norm I usually mash fairly low ~ 149-152 and this does the job for me.

As to your question of what effect this has for flavor in the final beer, again, since they are big beers, having an FG in the low teens, or lower results in a cleaner taste. Less cloying or syrupy like so many homebrews I have had.

Someone mentioned thermometer calibration. I was thinking the same thing because I can generally swing my FG anywhere I want based on where i mash temp wise. OG < 1.050 I go higher to hit 1.013-15. OG> 1.060 I go lower to push the FG down to 1.010-12.

EDIT: I completely missed Evan's first sentence in his first post in this thread. I guess I'm beating a dead horse with my post.

 

[menschmaschine]

To be honest I feel that you are attributing more affect to oxygenation than is warranted.

In direct contrast to your situation, I tend to end up on the low end of the FG continuum and I just don't worry too much about aeration. Yes I shake the carboy for a minute or so. But nothing more.

That's good stuff. Thanks for contributing. It's good to see that more people don't use pure O2 and still get high attenuation. Until this thread, I've only read from those who've spent money on an oxygen kit and most of them would be understandably biased.

I am very interested in the roll (if there is any) of minerals and attenuation... i.e., minerals that could be absent in very soft water and not contributed by the barley itself (or hops, for that matter), so if anyone has info on that, please share.

 

[menschmaschine]

Let me just add concerning flavor and attenuation since there are really two topics in this thread. What I'm asking about concerning flavor is how different methods of effecting attenuation affect flavor.

For instance, some Belgian styles can have the fermentation temp ramped up to get a higher level of attenuation. So, let's say you brew 2 side by side batches of the same Belgian style beer. All other factors being equal (same OG, etc.), one is brewed with a sacch. rest of 150 and has the temp. ramped up from 65 to 80°F during fermentation. It reaches an FG of 1.008. You brew the other batch with a sacch. rest of 145°F and keep the fermentation temp. steady at 70°F. This batch also reaches an FG of 1.008. Would these batches taste different? I wouldn't think the ester profile would be very different since the first batch, although going to 80°F, starts out at 65°F. So, what could be different (chemically)? Or would they be virtually the same?

 

[Bobby_M]

I think Evan! touched on it already but the oxygen thing is more an issue of getting enough yeast developed to do the job they would have already done. In average gravity, whatever yeast you pitch is probably enough to take it to the FG your sugar profile will allow. Sure, as you inch up to higher gravity and/or pitch too small, the O2 will affect the FG to a point.

The real control is in the mash which is the direct cause of that sugar profile. If you mash at 156F and pitch a 2 gallon starter, you're not going to get 85% attenuation. The problem is, it's not easy to predict and thermometer calibration error even a few degrees off will not help.

On the flavor topic, everything I've read suggests that underpitching and then providing tons of O2 will result in more esters (yeast character) due to the reproduction cycle. However, underpitch by too much and they conk out before desired FG.

Pitch a crapload of yeast and you get a clean ferment with reduced esters but you know you'll hit the lowest possible FG based on your mash activity.

I suppose what your question/point is, how do you balance pitch rate with mash profile to arrive at both a desired FG and ester character. If so, my brain hurts.

 

[SpanishCastleAle]

What I'm asking about concerning flavor is how different methods of effecting attenuation affect flavor.

From Kaiser's Understanding Attenuation page:

The limit of attenuation is set by the wort production and the difference between the final attenuation and the limit of attenuation is set by the fermentation.

It seems that if you were low on FG because the limit of attenuation was low then you'd have more unfermentable sugars in the wort (and final beer) but most of the fermentable sugars would have been fermented. So that sounds like lots of mouthfeel/body/head/etc. more than 'sweetness'. But if you were low on FG because of a large difference between the final attenuation and limit of attenuation then you'd have more unfermented fermentable sugars in the wort. And since the simpler, fermentable sugars are typically sweeter tasting than the more complex, unfermentable ones then I would expect a sweeter brew with less mouthfeel/body/head/etc. than the former.

EDIT: I'm just thinking out loud here...I may have it bass-ackwards.

 

[dontman]

For instance, some Belgian styles can have the fermentation temp ramped up to get a higher level of attenuation. So, let's say you brew 2 side by side batches of the same Belgian style beer. All other factors being equal (same OG, etc.), one is brewed with a sacch. rest of 150 and has the temp. ramped up from 65 to 80°F during fermentation. It reaches an FG of 1.008. You brew the other batch with a sacch. rest of 145°F and keep the fermentation temp. steady at 70°F. This batch also reaches an FG of 1.008. Would these batches taste different? I wouldn't think the ester profile would be very different since the first batch, although going to 80°F, starts out at 65°F. So, what could be different (chemically)? Or would they be virtually the same?

On the flavor topic, everything I've read suggests that underpitching and then providing tons of O2 will result in more esters (yeast character) due to the reproduction cycle. However, underpitch by too much and they conk out before desired FG.

Pitch a crapload of yeast and you get a clean ferment with reduced esters but you know you'll hit the lowest possible FG based on your mash activity.

I suppose what your question/point is, how do you balance pitch rate with mash profile to arrive at both a desired FG and ester character. If so, my brain hurts.

I will respond to this because it is a topic near and dear to my heart and experience. Big Belgians with a overt ester presence deliberately cultivated.

There are two things that have a huge impact on ester production and evidence in the final product. Ferment temp and (thank you so much for mentioning this Bobby. I thought I was the only one who understood this.) - pitching rates.)

As far as the temp effect on flavor, in order to get appreciable levels of ester production you have to have the early stage yeast operating in a warm environment. So in your example Mensch, there might or might not be a big difference depending on when you raise that temp. In order to get really good ester production I begin my ramp while the yeast is still multiplying. Which brings me to the point that Bobby mentioned.

Bigger is not always better. ?Yeast produce theri esters very early during the reproduction phase of the ferment. If you pitch too much yeast, too big a starter, or onto a yeast cake for example, then there is very little multiplying that the yeast needs to do and little opportunity for the yeast to spew out yummy esters. When I want a strong ester presence I do not underpitch exactly but I will definitely pitch less than I would say, for an ESB. It is a fine line to tread.

So in your specific example, yes, both samples could reach 1.008 AND have an entirely different flavor profile. For my Saison which I bottled last night I pitched the yeast (from a smallish starter) in 72 degree wort and then turned the aquarium heater up to 82. The ramp started immediately and by 48 hours the wort was at 78. By 72 hours it was at 82. I will get a huge ester presence.

At the same time I have a Belgian Pale in fermenter that was set at 70 for 3days and then dropped down to 64 for 19 days. This will have little ester presence.

A corollary to this above discussion is that if you want to use temp to increase attenuation WITHOUT seriously affecting the flavor profile then pitch a large starter and wait more than 72 hours before raising the temp. ( I think this is the mistake that a lot of brewers make when brewing would-be Belgians. They wait too long before raising the ferment temp and lose the opportunity for ester presence.)

 

[Kaiser]

It seems that if you were low on FG because the limit of attenuation was low then you'd have more unfermentable sugars in the wort (and final beer) but most of the fermentable sugars would have been fermented. So that sounds like lots of mouthfeel/body/head/etc. more than 'sweetness'. But if you were low on FG because of a large difference between the final attenuation and limit of attenuation then you'd have more unfermented fermentable sugars in the wort. And since the simpler, fermentable sugars are typically sweeter tasting than the more complex, unfermentable ones then I would expect a sweeter brew with less mouthfeel/body/head/etc. than the former.

You got it. That’s what I was about to write. Except for the part that the dextrins are responsible for the body and head retention.

Mensch, the key to understanding your problem is the fast ferment test. Only this can tell you the attenuation potential of the mash b/c it removes most fermentation factors by fermenting with a high pitch rate and high temp. If you deterimed that your mash is not the limiting factor you know that you have to tweak attenuation.

WRT to beers with the same attenuation but different limits of attenuation tasting different I can only attest to that. I currently have a Pils that had the FFT finish at 2.3 Plato and another one that had a FFT of 1.6 Plato. When the 2nd one was at 2.3 Plato it tasted much sweeter than the first one when it was at 2.5 Plato. And b/c of the FFT I know that the yeast still has some ways to go on the 2nd one. But I used WY2206 and this one poops out fairly early, so it has been a struggle to get the FG down. But WY2206 works well for Dunkels, Bocks and other beers that benefit from a larger limit of attenuation / attenuation difference.

Kai

 

[menschmaschine]

Thanks for the responses everyone. I'll check back later tonight. I've got to get SOME work done today!

 

[menschmaschine]

Wow, I just re-read this thread and there are lots of good posts here. This is cramming a lot into one thread, but it's still a good topic(s). Understanding this stuff can really take our beers to the next level.

Dontman, good post. I was aware of increased ester production with a lower pitch rate and/or higher fermentation temps early in the fermentation. But to take your statements to another level, what else is produced and why? Does the additional "heat" cause yeast to metabolize differently? We talk a lot on here about "ester" production, but what I think we really mean in addition to esters are fusel alcohols, diacetyl (and other ketones), phenol, and glycerol (from Fix).

Additionally, Fix (Principles of Brewing Science 2nd Ed.) does put significant emphasis on aerating wort. When discussing problems with attenuation, he cites "failure to dissolve an adequate amount of oxygen into the chilled wort" as a common problem among brewers. The question he doesn't answer here is how much O2? Is the saturation amount one can get from shaking/splashing (8 ppm, I believe) enough? Or does increasing that with pure O2 actually help with attenuation?

Now, regarding ester production, we should look at how it is produced. It is produced by combining a fatty acid and an alcohol. The catalysts to produce these are enzymes in yeasts. But what are the triggers for these enzymes to be active? High rates of yeast growth is one (in both highly oxygenated wort and poorly oxygenated wort). A higher concentration of fermentable sugars is another. Fix mentions all of this, but he does not mention fermentation temperature. But based on everything else I've read, we can assume higher fermentation temperatures (in the earlier stages) to have similar effects.

Back to attenuation and flavor, the ability for yeast to ferment various sugars vary from yeast to yeast (strain). I believe it is more proteins that result in increased head retention, as opposed to unfermentable sugars. So, do unfermented fermentable sugars (poor attenuation) taste different than unfermentable sugars ("full" attenuation). Both would result in sweetness and body, but is it a different sweetness and body for each?

 

[dontman]

Wow, I just re-read this thread and there are lots of good posts here. . . . snipped to show what post I'm replying to

I got the feeling from reading your posts before and this one confirms it, you have read as many texts as I have on the subjects we are discussing.

I find it interesting when reading texts that there are often as many different theses as when you ask a question on a forum. So something posited in a book as fact, you find out later, could have been conjecture or opinion.

That said and direct to your point. Yes the common reasoning given behind a slow temp ramp is to minimize fusel alcohols. And there is some accuracy to this. The question becomes: minimize fusels at what cost?

Two nights ago I cracked my first Chimay tripel clone from a batch. On this one I again ramped the temp immediately and hit 78 at shorter than 48 hours. When I bottled this batch the predominant flavor was hot alcohol with slight fruity background. 4 weeks later and the fusel alcohol is nothing but a warm note while the fruity esters are the predominant flavor.

So the point is that fusels can be fixed by aging and conditiong while esters cannot be back added.

As far as phenols and diacetyl, those are problems that show up on the other end of temp spectrum and since I am not a big lager fan I generally do not go there.

On attenuation and sugars, Kai and SpanishCastle answered this pretty well but I do disagree slightly in that I believe that in actual practice unfermentable sugars do two things at once: add to head retention and body and 2. add to sweetness. If they do not get fermented they do both, not either or.

So the point is that if you take a given wort and use a yeast that ferments it down to 1.025 and compare that to the same wort fermented with a different yeast that ferments it down to 1.016, then you will notice both increased sweetness and increased head and body in the higher FG beer.

I do understand that Lactose and Maltodextrine have differing levels of sweetness, as do other types of unfermentable sugars but the point is that the sweetness in each will still come forth in the final beer while the long chain molecules will also decrease the viscosity of the beer.

 

[SpanishCastleAle]

So, do unfermented fermentable sugars (poor attenuation) taste different than unfermentable sugars ("full" attenuation). Both would result in sweetness and body, but is it a different sweetness and body for each?

Generally speaking the simple fermentable sugars taste sweeter than the more complex unfermentable ones so I would expect more sweetness from the poor attenuation brew. In Kaiser's Pils experiment that appeared to be the case.

 

[menschmaschine]

So, to bring some of this together, and obviously none of this is black and white, but could we draw the following general conclusions?:

Unfermented sugars in the final beer (whether fermentable or not) result in body and sweetness. Unfermented fermentable sugars result in more sweetness than body. Unfermentable sugars result in more body than sweetness.
(I don't want to factor in head retention here because I'm not so sure residual sugars are a major player in head retention. I've had several batches with plenty of body/sweetness and very little head retention.)

Esters, since produced from fatty acids and alcohol, are produced in greater proportion to fusel alcohols if the temperature is increased relatively slowly after the start of fermentation. The balancing spot is when the yeast are still actively fermenting, yet there are already some alcohols present from which to produce these esters. If the temperature is ramped up too early, the fusel alcohols are produced in greater proportion and the yeast quit metabolizing sooner than there is time to reduce these fusel alcohols to esters.

 

[Kaiser]

Dontman, good post. I was aware of increased ester production with a lower pitch rate and/or higher fermentation temps early in the fermentation. But to take your statements to another level, what else is produced and why? Does the additional "heat" cause yeast to metabolize differently? We talk a lot on here about "ester" production, but what I think we really mean in addition to esters are fusel alcohols, diacetyl (and other ketones), phenol, and glycerol (from Fix).

Regarding ester production I once did an experiment that tried to show how O2 and pitch rate effecting the ester production. While outcome itself was inconclusive the introduction has a nice summary of the factors that effect ester production: Experiment Pitching Rate and Oxygenation - German Brewing Techniques

The question he doesn't answer here is how much O2? Is the saturation amount one can get from shaking/splashing (8 ppm, I believe) enough? Or does increasing that with pure O2 actually help with attenuation?

8 ppm is regarded as enough O2 for a proper fermentation assuming healthy yeast and an adequate pitch rate. O2 does help with attenuation as it allows the yeast to build sufficiently strong cell walls. The latter is important later in the fermentation as the alcohol increases and the yeast wants to strengthen their cell walls. This is a natural response to alcohol stress (experiments with yeast in an aerobic environment have shown that they increase the sterol production when alcohol is added). In a fermentation yeas doesn't have access to O2 when the alcohol is present in the beer. In this case they need to use their reserves and these reserves depend on the yeast growth that has happened so far and the initial O2 that was available. This is also one of the reasons why high gravity beers should be fermented with more yeast b/c it limits yeast growth and individual yeast cells will have more sterol reserves once the alcohol becomes a problem for them.

Back to attenuation and flavor, the ability for yeast to ferment various sugars vary from yeast to yeast (strain).

This is not the case. All brewing yeasts (ale and lager) can ferment glucose, fructose, sucrose, maltose and maltotriose. In addition to that lagers can ferment melibiose. But that sugar is only present in trace amounts and has no significance when it comes to attenuation levels. How the srains differ is their flocculation behavior and general efficiency in fermenting the sugars. Some are better than others when it comes to the fermentation of maltotriose which is the sugar that is most difficult to digest for the yeast.

I believe it is more proteins that result in increased head retention, as opposed to unfermentable sugars.

My position on dextrins and body is that dextrins have little effect on the body of the beer and that it is mostly proteins. I think that it just happens that more dextrinous worts are also richer in medium chained proteins. I once made a lengthy post about that but the search function in this forum really sucks now and I can't find it anymore.

I agree that this has been a really nice discussion and I'm glad Mensch brought this up. In essence the amount of residual fermentable sugars is important for the character of the beer and generally overlooked b/c you can't measure it unless you do the fast ferment test.

Kai

 

[menschmaschine]

This is not the case. All brewing yeasts (ale and lager) can ferment glucose, fructose, sucrose, maltose and maltotriose. In addition to that lagers can ferment melibiose. But that sugar is only present in trace amounts and has no significance when it comes to attenuation levels. How the srains differ is their flocculation behavior and general efficiency in fermenting the sugars. Some are better than others when it comes to the fermentation of maltotriose which is the sugar that is most difficult to digest for the yeast.

OK, I see your point. I guess what I meant to say was that different yeast strains metabolize different fermentable sugars and trisaccharides. I'm going from Fix's table in Principles of Brewing Science where he lists "Intrinsic Fermentability of Yeasts Strains":

1. Strong Attenuators- 78-80%- All fermentable sugars are metabolized. (Lager strains)

2. Medium Attenuators- 75-77%- Minor fermentable sugars are not metabolized. (Most ale strains)

3. Low Attenuators- <75%- Minor sugars and some trisaccharides are not metabolized. (Few ale strains)

 

[Kaiser]

OK, I see your point. I guess what I meant to say was that different yeast strains metabolize different fermentable sugars and trisaccharides. I'm going from Fix's table in Principles of Brewing Science where he lists "Intrinsic Fermentability of Yeasts Strains":

1. Strong Attenuators- 78-80%- All fermentable sugars are metabolized. (Lager strains)

2. Medium Attenuators- 75-77%- Minor fermentable sugars are not metabolized. (Most ale strains)

3. Low Attenuators- <75%- Minor sugars and some trisaccharides are not metabolized. (Few ale strains)

I don't think this is correct. Many sources that tell otherwise. It is true that many ale strains are poor maltotriose fermenters but they certainly can ferment it. Let me resurrect an English ale yeast and I'll try it in a fast ferment test against a lager yeast w/ the same wort. Note that this test does not resemble actual beer fermentation conditions but is designed to make the yeast eat all the sugars that they can eat.


Kai

 

[menschmaschine]

Possibly this is splitting hairs, but... so you're saying that attenuation variation among yeast strains doesn't have anything to do with what sugars that strain can and can't metabolize, it's how effective it is at metabolizing specific sugars?

Noonan specifies only between ale and lager strains stating that ale strains can ferment glucose, fructose, mannose, galactose, maltose, sucrose, xylulose, maltotriose, and partially ferment the trisaccharide raffinose. Lager strains, in addition to those sugars, can ferment melibiose and fully ferment raffinose.

Since all but monosaccharides must be reduced by enzymes in order to be fermented by the yeast, I would think there would be variation among yeast strains to have/produce these enzymes... perhaps not so much that they can or can't, but that some strains are better at it than others. Am I on the right track here? What exactly does cause, for example, Nottingham yeast to attenuate more fully than Windsor yeast?

Now, on an off-shoot of this topic, and as I mentioned earlier in this thread concerning minerals in brewing water and attenuation... do you know if there are metals/minerals necessary for the yeast (perhaps to do with the production or activity of the enzymes used to break down disaccharides?) to attenuate more fully? That is, are there metals/minerals typically found in enough quantity in brewing water, and not supplied by barley or hops, that are beneficial for yeast and their ability to metabolize sugars? Are there minerals necessary in the mash specifically for beta-amylase enzymes typically found in water and not supplied by the barley itself? (Keeping in mind that calcium and potassium are the 2 most abundant minerals in barley.)

I ask this because here is my water profile (units = ppm, except pH obviously):
pH: 5.7
Na: 3
K: 1
Ca: 2
Mg: 1
Total Hardness, CaCO3: 9
SO4: <1
Cl: 4
Carbonate, CO3: <1
Bicarbonate, HCO3: 9
Total Alkalinity, CaCO3: 7

I don't add anything to the mash (and I've never done an iodine test) because my efficiency has always been so high and with a pH that low, I figure it doesn't take much for the mash to get to optimum range. Is it possible that this water is so low in minerals that it may be affecting beta amylase enzyme activity or yeast metabolism (I usually add some quantity of gypsum to the boil).

I was thinking about doing an experiment, perhaps with 3 small mashes (french press coffee maker) to see if there is a difference in attenuation. 1 with distilled water & pilsner malt, 1 with store bought bottled water (of known water analysis) and pilsner malt, and 1 with bottled water, pilsner malt, and hops. Thoughts?

Seriously, you should write your own book. I'd buy it.

 

[Piotr]

I have a question about those simple sugars left in fermented beer. Will they be eventually eaten up by yeast in the bottles? Do I have to take into account this residual under-attenuation when calculating amount of priming sugar?

 

[menschmaschine]

I have a question about those simple sugars left in fermented beer. Will they be eventually eaten up by yeast in the bottles? Do I have to take into account this residual under-attenuation when calculating amount of priming sugar?

We'll have to wait until Kaiser gets back on here, but I can say this: I've bottled many batches that I felt could have gotten better attenuation (yet was sure fermentation was complete) and never accounted for residual fermentable sugars... and never had a problem with overcarbonation.

Were there fermentable sugars still in the beer? I don't see why not, but I think this goes back to what Kai and I were discussing above. Is it that these particular yeast in this particular fermentation have fermented all the types of sugars they're "willing" to ferment, regardless of whether or not there are still minor fermentable sugars left in the beer? I don't know what else to think.

 

[Kaiser]

I have a question about those simple sugars left in fermented beer. Will they be eventually eaten up by yeast in the bottles? Do I have to take into account this residual under-attenuation when calculating amount of priming sugar?

Those sugars left in the bottle are not that simple. We are talking mostly maltotriose here and the yeast that is left has given up on that residual amount. I know that lager yeast for example will slowly work on them and that a lager left on the yeast for too long can actually dry out more than it should. I'm not sure if the same thing happens with ale yeast or if the yeast will slowly die before it gets to eat the residual sugars.

When we bottle we add glucose or sucrose which is metabolized very easily by the yeast and once it is gone the yeast will again stop fermenting.

I wonder how this would change if you were to carbonate an english ale with Kraeusen that adds fresh health yeast. If that new yeast will go further in the bottle than its previous buddies went in the fermenter. But I haven't brewed and bottle conditioned English beers yet only APA, IPA and German Ales. And all of them were completely fermented (no or only little residual fermentable sugars) in the bottle.

Kai

 

[Kaiser]

Let me resurrect an English ale yeast and I'll try it in a fast ferment test against a lager yeast w/ the same wort. Note that this test does not resemble actual beer fermentation conditions but is designed to make the yeast eat all the sugars that they can eat.

Here is what I did:

3 Fast Ferment tests. One w/ WLP002, one with WLP830 and one with bread yeast. The OG was 11.5 Plato and i fermented them at 75F for 5 days with occasional shaking. The samples were pretty clear at the end and the yeast has settled at the bottom:

WLP002: FG=1.8 Plato
WLP830: FG=1.9 Plato
bread yeast: FG=2.3 Plato.

I didn't expect the bread yeast to lag that much behind, but the ale and the lager are very close and the 0.1 difference is within the measurement error. This shows that ale and lager can basically ferment the same wort sugars.

Kai

 

[menschmaschine]

Here is what I did:

3 Fast Ferment tests. One w/ WLP002, one with WLP830 and one with bread yeast. The OG was 11.5 Plato and i fermented them at 75F for 5 days with occasional shaking. The samples were pretty clear at the end and the yeast has settled at the bottom:

WLP002: FG=1.8 Plato
WLP830: FG=1.9 Plato
bread yeast: FG=2.3 Plato.

I didn't expect the bread yeast to lag that much behind, but the ale and the lager are very close and the 0.1 difference is within the measurement error. This shows that ale and lager can basically ferment the same wort sugars.

Kai

These are surprising results. White Labs lists WLP002 at 63-70% attenuation and you got 84%. What was the mash temp, fermentation temp? I'm assuming German Pilsner malt. Any idea why 002's attenuation was so high?

 

[Kaiser]

Any idea why 002's attenuation was so high?

b/c it was fermenting under ideal conditions for the yeast (high temp and high pitching rate). Both yeasts can ferment the same sugars (except for a few that are not present it wort at significant amounts) and the only thing that keeps the WLP002 from getting close to the performance of the WLP830 in practical fermentations is it's strong flocculation behavior and that it likes to give up early.

the mash profile was

35 min @ 63C
45 min @ 70C
15 min @ 75C

limit of attenuation was 84% and I plan to have the beer attenuate to at least 82% if not closer to 84% as I want it to have as little residual sweetness as possible. After all it's a Pilsner.

Kai