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Old 11-21-2012, 11:11 PM   #1
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Default No/low aeration. Just more yeast?

I'm sure this has been discussed many a times, but I couldn't find an exact answer when using the search function. I have yet to order an O2 kit, but I'd reeeeeally like to brew this week and was wondering: How much can just pitching more yeast make up for sub-par O2 levels?

In this particular case, I'd like to brew a 10-12% RIS and have plenty of US-05 slurry that I can pull off a low gravity blonde. I've generally just been splashing/pouring aggressively into the fermentor so far, which obviously isn't a lot of O2 for this big of a beer.

Will just pitching a ton of yeast work? What kind of off-flavors (if any) might I run into?

Thanks in advance!

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Old 11-21-2012, 11:19 PM   #2
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Originally Posted by CharlosCarlies View Post
I'm sure this has been discussed many a times, but I couldn't find an exact answer when using the search function. I have yet to order an O2 kit, but I'd reeeeeally like to brew this week and was wondering: How much can just pitching more yeast make up for sub-par O2 levels?

In this particular case, I'd like to brew a 10-12% RIS and have plenty of US-05 slurry that I can pull off a low gravity blonde. I've generally just been splashing/pouring aggressively into the fermentor so far, which obviously isn't a lot of O2 for this big of a beer.

Will just pitching a ton of yeast work? What kind of off-flavors (if any) might I run into?

Thanks in advance!
You still probably don't want to over pitch by much, but you are going to want to shake the heck out of your wort. Minutes and minutes of shaking. I would say use the correct amount of slurry (per your favorite calculator) or slightly more than called for (say 10% more?). The beer will likely turn out fine, but it may finish higher than average and take longer to finish.
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Old 11-21-2012, 11:31 PM   #3
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There is no doubt it will be stressful on the yeast. Overpitching will increase the ester profile of the beer, which may not be a bad thing. However, what you could do is re-aerate about 18 hours into fermentation. What this does is reintroduces oxygen for the yeast to consume, this helps the fermentation greatly in bigger beers.

What I used to do before I had propper aeration equipment was pour the cooled wort into half gallon mason jars and shake the crap out of them. I figure this got me to around 7ppm tops since that is about all you can acheive with out pure oxygen. I would recommend being aggressive with the shaking to get as close to that as possible. For bigger beers, about 18 hours in the yeast will have used all available oxygen, and if more is not available they will be stressed and this can increase the phenols in your beer. Simply adding more oxygen at this point can greatly increase your attenuation and happiness level of your yeasties. Don't worry about oxydation at this early of a point in a bigger beer, the yeast wont allow it to happen as they still are searching for any available o2 and will use it rapidly. You do want still want to use aeseptic practices as best as possible, but at this point the yeast is so active infection is not likely if you are cautious and sterile

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Old 11-21-2012, 11:36 PM   #4
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Overpitching will increase the ester profile of the beer
I could be totally wrong here, but I was under the assumption that under-pitching had a greater effect on ester profile. Am I way off?

Also, isn't the ester profile generally more heavily influenced during the aerobic/growth phase? If so, wouldn't low O2 levels just result in a faster start to actual fermentation?

Quote:
you are going to want to shake the heck out of your wort
Well, that's really the problem. I'm putting 15g of wort into a Brewhemoth, so it's pretty hard to shake around very much.
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Old 11-21-2012, 11:44 PM   #5
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And this is definitely assuming I'm pitching very active/healthy yeast from a previous non-stressful fermentation.

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Old 11-22-2012, 08:38 PM   #6
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Originally Posted by CharlosCarlies View Post
I could be totally wrong here, but I was under the assumption that under-pitching had a greater effect on ester profile. Am I way off?

Also, isn't the ester profile generally more heavily influenced during the aerobic/growth phase? If so, wouldn't low O2 levels just result in a faster start to actual fermentation?



Well, that's really the problem. I'm putting 15g of wort into a Brewhemoth, so it's pretty hard to shake around very much.

When yeast has to grow/reproduce it uses up all the available acyl Co-A, which inhibits etster formation. Therefor under pitching results in lower seter formation because yeast is busy reproducing and using up the acyl Co-A which is critical for use in ester formation. Over pitching results in far lower reproduction and therefore more Co-A becomes available for ester production.

So to answer your question, under pitching has a very significant effect on ester formation, just not in the way many would think, since it inhibits it.

As far as O2 is concerned, view ester formation in this way - nearly anything that slows yeast growth will increase the ester production. Ie, over pitching, poor aeration, little nutrient etc. Increases in temperature also increase ester produciton.
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Old 11-22-2012, 08:43 PM   #7
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Also, in regards to having 15 gallons and not being able to shake it. Simple solution, siphon off a few gallons and re-aerate those few gallons (be sterile and you'll avoid infection). The yeast will already be well under way, so they will not require huge amounts of o2 at this stage, too much could cause oxidation. However, adding some o2 will give your yeasties an extra boost and give you better attenuation. Also, try raising the temperature a few degrees for the last 1/3rd of the fermentation. During the first 2/3rds of the fermentation, the majority of the flavor compounds have already been produced, so warming will have little to no effect on flavor. However the warmer temperatures will increase yeast activity creating a better environment for yeast to 'finish up' doing things like cleaning up Diacetyl, and Acetaldehyde

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Old 11-22-2012, 08:45 PM   #8
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Maybe look at WLP099 Super High Gravity Yeast...has very high alcohol tolerance too.

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Old 11-22-2012, 08:48 PM   #9
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Originally Posted by CharlosCarlies View Post
I could be totally wrong here, but I was under the assumption that under-pitching had a greater effect on ester profile. Am I way off?

Also, isn't the ester profile generally more heavily influenced during the aerobic/growth phase? If so, wouldn't low O2 levels just result in a faster start to actual fermentation?



Well, that's really the problem. I'm putting 15g of wort into a Brewhemoth, so it's pretty hard to shake around very much.
This may help: Pitching Rates

This addresses underpitching, overpitching, esters, oxygenation, fusels, etc.
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Something is always fermenting....
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Primary:
Brite Tank/Lagering:
Kegged: Hefeweizen, Chocolate Hazelnut Porter, Kumquat Saison, Tart Cherry Cider, Belgian Tripel, Maibock Bock, Ommegang Abbey Ale Clone, Belgian Golden Strong, German Pils (WLP830)
Bottled: Belgian Quad (Grand Reserve), Derangement (Belgian Dark Strong)
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