| Author |
Message |
    
Astro
Junior Member
Username: Astro
Post Number: 87
Registered: 07-2004
| | Posted on Saturday, June 11, 2005 - 06:14 pm: | 
|
No, I'm not trying to emulate Fredrik... but I think I have a pretty good experiment going on. A few days ago I brewed an 11 gal batch of pilsner and split it between two carboys. Both carboys are identical with OG of 1.055. Both got a good bit of aeration as I pumped the wort through my CFC and into the carboys (about 6-8 inches of foam). Not relying on that alone, though, I hooked up my O2 bottle/airstone and gave the first carboy about 2 minutes of oxygenation. I started on the second carboy and the bottle of O2 ran out after about 30 seconds. I figured this was probably enough, so I went ahead and pitched the yeast. Temperature of the wort and the 1 gallon starter was 50 degrees.
Now for the interesting part. The carboy with more oxygen took about 24 hours before active fermentation. The other one took about 48 hours. Once it got going, it looks identical to the other. Both are chugging along steadily right now. It will be interesting to chart their progress, and see if i can find any differences in the two batches, other than the lag time.
I know this seems like I'm stating the obvious, but I learned a few things. I'd always heard with pure O2 that you only needed about 30-45 seconds. Obviously, the wort benefits from longer exposure than this. I'd never noticed before because I've always pitched large starters into warmer wort and they always took right off. This was my first try pitching into a 50 degree wort, so the longer exposure to O2 was far more obvious. Also, I've heard of folks who just count on the splashing while filling up the fermentor to aerate the wort. I'm now a believer that this is far from sufficient (although who knows - maybe the end product will be the same but just take longer).
Maybe this was interesting only to me, but I thought I'd share. |
Denny Conn
Senior Member
Username: Denny
Post Number: 4734
Registered: 01-2001
| | Posted on Saturday, June 11, 2005 - 06:18 pm: |
|
I assume it was the same type and amount of yeast in each carboy?
LIfe begins at 60...1.060, that is.
|
Astro
Junior Member
Username: Astro
Post Number: 88
Registered: 07-2004
| | Posted on Saturday, June 11, 2005 - 06:40 pm: |
|
You bet. Wyeast 2278, split between the two. Both are identical, with the exception of the O2. |
Ken Anderson
Advanced Member
Username: Ken75
Post Number: 856
Registered: 11-2002
| | Posted on Saturday, June 11, 2005 - 06:42 pm: |
|
Could be that since the one was already saturated with O2, it more quickly out-gassed the produced CO2, because the CO2 had nowhere else to go. The less saturated wort, on the other hand, could hold more produced CO2 before finally becoming saturated and expelling it. Thus the perceived difference in "lag time." |
Graham Cox
Member
Username: T2driver
Post Number: 151
Registered: 11-2004
| | Posted on Saturday, June 11, 2005 - 07:55 pm: |
|
"I'd always heard with pure O2 that you only needed about 30-45 seconds."
I always shake my head when this subject comes up. Time is not a measure of O2 concentration.
There are a number of other variables that affect the level of O2 that actually ends up in the wort, such as the size and shape of the stone, the pressure and thus the rate at which it is applied, the temperature and gravity of the wort, etc. Two people with two different setups will achieve different results from an identical application solely measure by time.
If one removes the pressure (rate) variable by running it wide open, one pisses away a large percentage of one's O2 right out the top of the fermenter.
Personally, I adjust mine in my bucket of Star-San until I get what I deem to be the right stream of bubbles, then quickly transfer it into my wort and let it go for 2-3 minutes. Seems to work for me, and my bottle has lasted almost a year - and that's using it in main batches and starters. (I use the red disposable kind with the brass screw-in regulator.) YMMV. |
Fredrik
Senior Member
Username: Fredrik
Post Number: 2310
Registered: 03-2003
| | Posted on Saturday, June 11, 2005 - 08:17 pm: |
|
Interesting test, Astro. Thanks for posting!
The solubility of gases does not compete for space as such. Each gas would be in equilibrium with it's own spiece in the liquid phase. Though, in some cases the level of compound A, may affect the solubility of compound B. But considering that the solubility of O2 and CO2 differ by like 6 orders of magnitudes I don't think the impact of the O2, on the CO2 solubility is a significant factor.
Assuming the batches were identical I would not be surprised if the difference was due to the difference in oxygen supply.
This was a quite low temperature (50F), and I think the performance at low tempereature probably calls for more UFA's and thus oxygen than it does a room temp.
I heard another story of a brewer that underpitched by a factor of 20, and still attained almost excellent performance. I had hard to believe it at first, but eventually he mentioned that "btw" he had roused his carboyed periodically until bubbling started. Probably some 24 hours. Once that lag was passed, it fermented out in just a few days, as if he had used proper starter. This was in effect an extended aeration. The oxygen in the headspace is more than enough! It is just that he repeated the admittedly inefficient (aeration by shaking). This also shows that it's not the peak ppm that you are able to shove into your wort that matters, it's the accumulated amount of O2 actually beeing used by the yeast.
/Fredrik |
Astro
Junior Member
Username: Astro
Post Number: 90
Registered: 07-2004
| | Posted on Saturday, June 11, 2005 - 09:48 pm: |
|
"Time is not a measure of O2 concentration."
True, but it is the only thing I really have the ability to measure. I do the same as you as far as setting the flow rate first, then putting it in the wort. Although you shake your head, you yourself use time (2-3 minutes) to judge when you are done. I'm not sure where I read the 30-45 second ROT but I think that is not enough time, judging by what I've seen with this batch. Your 2-3 minutes sounds better to me. |
Graham Cox
Member
Username: T2driver
Post Number: 152
Registered: 11-2004
| | Posted on Saturday, June 11, 2005 - 10:30 pm: |
|
"Although you shake your head, you yourself use time (2-3 minutes) to judge when you are done."
Point taken, but I was referring more to the arguments people have regarding the "correct" amount of time. There is no "correct" amount of time unless you have devised a method of delivering the O2 at a perfectly consistent and repeatable pressure and then measuring the resulting O2 concentration achieved over a specific period of time with a dissolved O2 meter, a device most of us homebrewers don't tend to have.
Put another way, it varies from brewer to brewer and we can't measure the result directly anyway, so arguing over the correct length of time is pointless. What works for you in your brewery is all that matters. |
Nathan Eddy
Junior Member
Username: Nathan_eddy
Post Number: 35
Registered: 03-2005
| | Posted on Sunday, June 12, 2005 - 05:40 pm: |
|
I give my cooled wort a good whirl with my large brewing spatula (enough to create lots of foam). Then I pour it through my strainer/funnel. Then I give it another good whirl in the carboy, creating even more bubbles. Pitching on top of a previous yeast cake, I never have a batch that takes longer than 8 hours before it's fermenting furiously. I'm not sure I see a benefit in what you guys are doing. Please explain. |
Guy C
Intermediate Member
Username: Ipaguy
Post Number: 258
Registered: 09-2003
| | Posted on Sunday, June 12, 2005 - 05:47 pm: |
|
Happier yeast, especially in higher OG worts, which aids maximum attenuation and lessens possibilities of off-flavors resulting from stressed yeast, for one. |
Graham Cox
Member
Username: T2driver
Post Number: 155
Registered: 11-2004
| | Posted on Sunday, June 12, 2005 - 06:59 pm: |
|
"I'm not sure I see a benefit in what you guys are doing. Please explain."
There are many sources of information on this topic on this board, on the broader internet, and in dozens of brewing texts. I am not aware of any source that indicates that insufficient oxygenation of wort is a good thing.
In short, yeast need oxygen for cell wall building, health, and maintenance. If you grossly overpitch (such as pitching on an old yeast cake), the yeast do not need to multiply to any great extent, because they've already achieved optimum density in the previous batch. A short lag time in this instance is to be expected. The problem is, as Guy stated above, the yeast potentially have been stressed by multiple divisions (scarred cell walls are less efficient membranes), exposure to alcohol, and age. They're not young, vibrant, and healthy, but they often are able to overcome this handicap by sheer strength of numbers. Stressed yeast, however, tend to excrete bad things into your beer and then not clean up after themselves. Cell walls deprived of O2 for too long can become impermeable, resulting in incomplete and/or improper attenuation.
Will you beer ferment out by pitching on an old yeast cake? Probably, but not necessarily. Will it taste the same as one pitched with a more appropriate quantity of young, healty yeast cells that were given proper nutrients and oxygen? No, it will not.
Maybe the more estery flavor profile associated with yeast division is not the profile you want in every style. Maybe you're brewing a barleywine and you want all the yeast you can get. If so, brew on. If pitching every batch on an old yeast cake is how you like to brew beer and it works for you, then brew on. It's not how professional brewers tend to brew at any level, macro or micro, nor do they recommend this approach at the homebrew level in any text I've ever read. But whatever works for you is A-OK by me. |
ELK
Senior Member
Username: Elkski
Post Number: 1075
Registered: 01-2003
| | Posted on Sunday, June 12, 2005 - 11:21 pm: |
|
My SS sintered stone is on the end of an 18" length of 1/4" SS tubing and I find that If I just leave it in one place on the bottom of my plastic pail many bubbles come to the top and leave the scene. IF I slowly stir the wort the bubbles don't come to the top nearly as much. I also turn down the O2 pressure thus flow as any amount over a certain bubble rate just flows to the top and is gone. Usually 30-60 seconds threatens to fill my 1.5 gal of free headspace and I have learned that it is best to leave a couple of inches under the lid to lesson the chance of a foam over.
Using a fine O2 stone pruduces a fine bubble foam that is much different than the foam you get from stirring plus you know its 100% O2 instead of the 20% O2 in normal air. I usually pitch at 1-3pm on a brew day and I always have so much more fun and sleep so much better at bedtime knowing the airlocks are chugging away!!
Best thing I ever did was start using starters and O2..I should never have a lag time again.
ELK |
Fredrik
Senior Member
Username: Fredrik
Post Number: 2311
Registered: 03-2003
| | Posted on Monday, June 13, 2005 - 05:30 am: |
|
IMO, since it's hard to measure everything each time, O2, yeast etc. I rely on the *attained performance* and result as a receipt for my procedure.
The pitching rate and the aeration affect the fermentation performance as in fermentation time and also abit the attenuation. I think short lagtime is something different, and short lag does *not* prove that you have sufficient aeration. Big pitching rate but lousy aeration may give short lag, but an abnormal finish. To me, the ultimate "confirmation" to the procedure is the fermentation profile (rather than time alone) and attenuation. If my fermentation profile is abnormal, then in something, somewhere there is an explanation. Period.
I think of choosing aeration and pitching rate,
1) as to get a "decent" performance and attenuation first of all.
2) Then within reasonable performance limits, things can be tweaked to flavour preferences.
I think there are many ways to aerate, the difference in techniques are probably subtle. But the important thing is the final initial UFA/sterol levels your yeast acheives. At times, I think this is different from the peak ppm O2 you shove into the wort. If you can do this by quick O2 injections, or my multiple aerations with air, or pre-aeration of yeast, I think it's good enough ethier way. The final fermentation performance will probably tell you if it works or not.
/Fredrik
(Message edited by fredrik on June 13, 2005) |
Miker
Member
Username: Miker
Post Number: 208
Registered: 02-2003
| | Posted on Monday, June 13, 2005 - 06:48 pm: |
|
Graham said:
"Will you beer ferment out by pitching on an old yeast cake? Probably, but not necessarily. Will it taste the same as one pitched with a more appropriate quantity of young, healty yeast cells that were given proper nutrients and oxygen? No, it will not.
Maybe the more estery flavor profile associated with yeast division is not the profile you want in every style."
Maybe I just haven't been paying enough attention to this topic, but I honestly didn't know there was such a difference in the end product when pitching on "young" yeast vs. a yeast cake. I hope everyone here can discuss this topic further. Does everyone agree?
Also, Fredrik - when you speak about fermentation profile are you talking about your graphs showing attenuation over time or what? I have only looked at lag time and overall attenuation.
Incidentally, I usually aerate about 60 seconds with pure O2 and an airstone. Time was decided on by looking at a few experiments posted on HBD in the past. This seems to work well for me at least as far as short lag times and good attenuation. But then I don't really see much difference when I don't have the oxygen and just shake the bejesus out of the carboy. |
Fredrik
Senior Member
Username: Fredrik
Post Number: 2312
Registered: 03-2003
| | Posted on Monday, June 13, 2005 - 07:38 pm: |
|
About old vs young yeast, I think this is an issue mainly if you overpitch in the sense that when you overpitch alot, then there aren't enough food to have all all cells go through a complete budding cycle, and if you keep cycling this procedure - repitch the entire yeastcake from overpitched batches - you get more and more dead cells, and more and more old cells.
I think the problem isn't to reuse yeast! the problem might be if you systematically overpitch. Overpitching leads to larger population of old, damaged and dead cells since the relative regeneration of young cells is smaller in each batch.
IMO, I think using an entire yeast cake at least for a normal gravity beer would quality as overpitching.
The recommended pitching rates are designed to give good performance, yet give some regeneration.
1 million/ml/P means each cell on average goes through 3 complete cell cycles. At EOF the original cells make only 12% of the population.
A full viable yeast cake would probably mean there is barely enough food for each cell to make it through one cell cycle. A full yeast cake of starved cells probalby has alot of maintenance to do as well possibly decreasing the food left for regeneration. In this case the original and possible crappy yeast still probably makes more than 50% of the population.
I never tried to pitch that much yeast so I have no experience on the practical order of significance, but the idea of overpitching *in particular* with old and less healthy yeast is not appealing to me. I think a balanced pitching rate is probably best. That said I think there is a wide range of pitching rates and aerations that gives great beer, where it's merely a matter of taste. No more strange that some people like some slight diacetyl in some beers and some don't.
With fermentation profile I mean the shape of the fermentation activity over time. Often this may correlate with the fermentation time, but I avoided that since there might be exceptions, and clearly temperature affects fermentation time as well. The profile can tell a whole lot.
For example I have several times examined the fermentation profile of a normal wort, with wort diluted with sucrose, the shape of the graph is indeed strikingly different, but the primary time might be longer too, but I consider the shape to tell more than the time alone. If you look only at primary time you may need another reference.
I think some keys are. Lagtime, time-stamp for peak, attenuation at peak, and time to for practical purposes full attenuation.
/Fredrik |
Guy C
Intermediate Member
Username: Ipaguy
Post Number: 259
Registered: 09-2003
| | Posted on Monday, June 13, 2005 - 09:38 pm: |
|
I believe there can be negative consequences to using a very high pitching rate of healthy yeast cells too, at least commercially. A Lagunitas brewer mentioned one thing that happens with future repitches of previously "overpitched" yeast is that they get "lazy" and floc. out too early, which can lead to under-attenuation and potential off-flavors from compounds that aren't cleaned up by yeast due to the reduced time they remain in suspension. |
Heath
Member
Username: Frizedo
Post Number: 175
Registered: 09-2004
| | Posted on Monday, June 13, 2005 - 09:39 pm: |
|
I never force airate, or shake my wort. Yet somehow my beer always starts within a 24hr period and finishes at a reasonable rate. Only thing I do is pitch big. So I think Ill save my stone for force carbing and the O2 tank for high altitude brewing.
Heath |
Fredrik
Senior Member
Username: Fredrik
Post Number: 2313
Registered: 03-2003
| | Posted on Tuesday, June 14, 2005 - 05:58 am: |
|
> I believe there can be negative consequences to using a very high pitching rate of healthy
I agree. I see not point in overpitching. I am convinced you can get excellent performance with normal pitching rates if the yeast is well prepared.
/Fredrik |
Brandon Dachel
Senior Member
Username: Brandon
Post Number: 1543
Registered: 03-2002
| | Posted on Tuesday, June 14, 2005 - 06:05 pm: |
|
> I never force airate, or shake my wort.
Niether do I. However I do build my starters on a stir plate so there is alot of well-oxygenated yeast. |
|
Brews and Views Archive 2005 
Closed: New threads not accepted on this page