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Old 11-11-2008, 08:28 PM   #1
mandoman
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Default pondering the whole yeast thing

OK. I'm a convert. i believe everyone when they say we underpitch and we should pitch larger volumes of yeast using more dry yeast, or preferably, large starters from liquid yeasts at the 100 million cells per plato per ml or whatever. I get that. i also get that we should ferment in a primary for 10 days to 14 days, even longer, and that yeast should be oxygenated at the beginning of the ferment. What I don't get is how we ASSESS our fermentation.

The variables (responses) I see being used, and use myself, are quantitative and qualitative observations of the fermentation process. On the quantitative side we have gravity. We record starting gravity, we have an idea of what the finishing gravity will be, and we consider fermentation 'finished' when the FG is consistent for several days (does not decrease further). We also quantify temperature as being A) the right target (e.g., 68 for US 05) and B) consistent (i.e., the same temp the whole time, not up and down). Further, we observe qualitative parameters including: quick start of fermentation. Seems most people consider fermentation to be better if it starts quicker. Within 24 hrs is good, immediately is better. We also qualify things like fermentation 'activity' lots of airlock bubbling, churning of the beer in the fermenter, etc. are good things.

I'm sure I'm forgetting some things. But, having said these things we would consider a good fermentation to A) attenuate fully, B) adhere to consistent and correct temperature, and maybe C) require an approximate amount of time (e.g., 3-5 days for ale at XX OG, or 7-10 days for lager at XX OG) where more or less days to ferment could indicate something is wrong.

here's where I'm having trouble. I can seriously underpitch with say, one vial of WL 001 in a 1.070 pale ale and A) ferment at 68, B) completely attenuate at 4-5 days but leave in the fermenter until day 14, and C) aerate just by shaking or using an aerator attachment to end of cfc and get a great beer, right? We all have done this. I could also end up with some issues with this beer. For example, I just did essentially this brew and ended up with some diacetyl.

Now the confusion. I could also have done the same beer and aerated, pitched a large 4 L starter, and had consistent and correct temps. In other words, there would be no quantitative or qualitative differences in the fermentation process (e.g., temperature, attenuation, activity) to indicate a difference. Of course, the beer could have off-flavors LATER. Are there no ways to 'measure' a bad fermentation? I read a lot about beers 'not attenuating fully' or 'not finishing' or 'having a lag time before fermentation starts'. These are all solid observations that something is wrong with the process.

I guess what I'm looking for are the solid, observable, even quantifiable indications of less-than-desirable fermentation. Is it diacetyl? How do we 'KNOW' that aeration and temperature are so critical if there's no way of quantifying this????

I've seen the yeast life cycle things. I've read jamil and palmer and daniels. I've had microbiology. There is a lot of great information out there, don't get me wrong, but the fermentation thing seems a little hocus-pocusy for lack of a better term. Are we just trying to give the yeast what we 'think' they want - and how do we know what they want?

I'd be interesting in a discussion about this, or at least an education.

cb

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Old 11-11-2008, 08:56 PM   #2
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This is why you need to do brew processes that are measurable and repeatable. Then when you change a process, change it one at a time so that the direct effect can be notated. Otherwise it is all just one big guessing game.

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Old 11-11-2008, 10:16 PM   #3
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Ultimately, as much as we try to apply science to brewing, we are still working with living organisms. Therefore, there will be a small amount of unpredictability.

Underpitching can stress yeast. What a starter is supposed to do is provide enough cells so the yeast don't have to reproduce when they hit the wort. They can just start eating away. Stressed yeast add a number of off flavors which can include diacetyl. Underpitching will have less to do with proper attenuation.

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Old 11-11-2008, 10:39 PM   #4
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I agree, who can predict biology? I also agree that repeatability is what we're aiming for. It's just hard what with the lag time and all. I guess part of what I'm saying is, if I grossly underpitch, provide little to no oxygen to yeast, ferment warmish and maybe even up and down, I'll still get 'good attenuation' in a 'normal amount of time'. In fact, this scenario may 'behave' exactly like a well pitched and aerated batch. If the yeast don't have enough oxygen, wouldn't one expect they would get a bad start/not finish/be slower? Something? It's a touch price to pay to find out weeks later that there's some diacetyl. Now I'm whining and also seeing the logic in 'prevention is worth an ounce of cure' or whatever. I suppose trying your best to do what is at least believed to be accurate gives you the lowest propensity for a bad result?

cb

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Old 11-11-2008, 11:15 PM   #5
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Of all the factors you listed, lag time is the most ambiguous. That is the least of my worries. If I know I made my wort at the correct mashing steps, oxygenated, pitched enough healthy yeast and have fermentation at the correct temperature, then the yeast are going to get to work.

In the end you cannot directly "control" the yeast, but you can provide an environment that will encourage all of the proper fermentation procedures. All of those other factors do have some quantifiable range to work with.

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Old 11-12-2008, 01:15 AM   #6
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so if i undertand what you're saying, your issue is that there are few if any observable indicators that problems with your process (pitching rate, aeration, temp) are going to negatively affect your beer. and those things which can be observed (long lag time, unexpected gravity readings, etc.) don't correspond 1 to 1 with specific problems in your process?

if so, that's definitely true. it can frustrating to be more or less in the dark about the finished product until the end of the process. that's why homebrewers stress consistency in every controllable aspect of the process. things like pitching enough yeast, controlling temp and aeration aren't just what we think yeast want, they've been proven over time and verified in lab tests. alot of the specific process of fermentation is still unknown, sure, but a consistent process that utilizes the science we do have will produce consistently good beers.

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Old 11-13-2008, 12:32 AM   #7
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john,

yeah, i think i'm on that steep slope stage where the rate at which I'm learning far outcompetes the rate at which I'm brewing so every brew I'm trying several new things. Most of which I am keeping as part of my process - cooler fermentations, larger pitches, etc. But the actual mechanistic parts of the process I'm varying as well as general procedures. And it's just because I'm thinking and reading and only brewing once every week or two. I just followed my oatmeal stout fermentation using WL 002 which is such a different yeast than what I've been using. I never would've thought to pay attention to the yeast behavior. In this case I mean aspects of behavior I can't watch or see but that I can measure indirectly using the hydrometer. This beer started at 1.060 and finished at 1.020. That's WAY higher than I'm used to a smallish beer finishing, but that's cuz I've been using US 05 or WL 001. This is cool ****!

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Old 11-13-2008, 01:18 AM   #8
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Quote:
Originally Posted by mandoman View Post
I agree, who can predict biology? I also agree that repeatability is what we're aiming for. It's just hard what with the lag time and all. ... It's a touch price to pay to find out weeks later that there's some diacetyl. Now I'm whining and also seeing the logic in 'prevention is worth an ounce of cure' or whatever. I suppose trying your best to do what is at least believed to be accurate gives you the lowest propensity for a bad result?

cb
Sure you can predict it. All you need is a conical fermentor setup so that you can sample your yeast. A french press to extract the yeast constituents and then a gas chromatography setup to analyse etc etc. It should only run you a couple hundred grand.

The key is how can you make the best beer within the limits of your budget and resource constraints. Sometime we just have to do things "rule of thumb" and hope for the best without being able to evaluate carefully because we are HOMEbrewers.

Mind you I would love to have a simple test or measure that would help sort out problems early.
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Old 11-13-2008, 01:52 AM   #9
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i hear you on the near impossibility to change ONLY one thing at a time when you're starting out. most people want to try their hand at different styles and are amassing new equipment and techniques at a rapid rate, which makes consistent process all but impossible for the first few months.

i've only recently started doing a couple "house beers" that i intentionally try to do the same way every time. of course, some things are always a little different. i don't have a keezer so fermentation temps are always approximate, i make starters from washed yeast so the cell counts are somewhat variable. i get similar, but not exactly identical hops and grains. but there's enough consistency there that i can now predict how fermentation will go, what the krausen will look and smell like, when the beer will drop clear, it's very empowering

so good luck and enjoy, it took ~8 months for me to start really "getting it," but now i feel a lot more in control of my beers and more confident when i do try to create new ones.

p.s. wlp002 finished high for me too. it made a nice beer, but i've been brewing my stouts with wyeast 1056 as of late. not because it works better but because i enjoy the finished product more. it is cool ****!

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Old 11-14-2008, 01:24 AM   #10
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Quote:
Originally Posted by mandoman View Post
I've seen the yeast life cycle things. I've read jamil and palmer and daniels. I've had microbiology. There is a lot of great information out there, don't get me wrong, but the fermentation thing seems a little hocus-pocusy for lack of a better term. Are we just trying to give the yeast what we 'think' they want - and how do we know what they want?
There's a lot of "what ifs" in your post....and well, I think good brewing is like good cooking. There isn't just one way to have good results. Which ever methods you chose, a lot of it is experience and intuition. I do believe in having a little bit of both....must be from my mom (who is an excellent cook). You need some experience to know at what temp you want your particular yeast to ferment....you'll need some intuition to know what kind of attenuation you need for each particular style. At least with my own endeavors at starters...I've found that large cell counts are important for certain styles of beer: and actually can be detrimental to a few (a few of my beers I've found actually "taste" better with a slow ferment). That's where I think Charlie Papazian's idea of being open to anything helps. The more I get into beer, the more I see it parallels bread making: light and fluffy is an appropriate style as is dense and crisp. Boy, I'm getting very philosophical here...but I think going for a set prescription is only one possibility: and doesn't automatically lend itself to more reproducible results. Since there are so many styles and variables....I think having some experience and intuition goes a long way.
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