Better attenuation through constant aeration?

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Better attenuation through constant aeration?

Postby xxxx » Mon Jul 17, 2006 10:55 am

Hello,

I have a general question in terms of maximizing my yeast attenuation. My beers are usually sweeter than I would like, and I think maybe my yeast is not quite living up to it's potential. Assuming a 7 day fermentation primary, is it acceptable to shake the bucket a few times a day for the first 5 days to make sure the yeast isnt getting "lazy", then still allow for 2 days so it can settle out? The only reason I thought of this was I was researching a white labs super high gravity yeast, and they recommend a procedure kind of similar to this.

I also shake up my starter a few times a day as well, to make sure thats going well.

Do you think this will have any impact, for good or for worse? Or am i just wasting time and effort?

Thanks for your thoughts!
xxxx
 
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Postby stardrive » Mon Jul 17, 2006 8:56 pm

I don
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I would look at your transfer process

Postby cleone » Wed Jul 19, 2006 11:12 pm

I would agree with stardrive (last post). I have never had to shake or otherwise push my yeast into fully attenuating. Without knowing more about the details of how you are transferring your wort to the primary and adding your yeast, etc I would suggest taking a closer looks at the transfer (to the primary) process.

1. Are you sufficiently aerating your wort? I pour my wort from kettle to primary while holding the kettle about 4 feet above the primary. Making sure to maximize the splashing/aerating during this process. Once in the primary, I make sure to stir and spash for a few minutes (again aerating the wort).

2. Are you cooling your wort to within the target fermentation temp for the yeast being used? Excessively high wort temps when adding your yeast can kill yeast and affect your attentuation. I make sure the cool my wort to a max of 80 degrees (preferably down to 70 for ale, lower for lager yeast).

3. Just to give you a baseline, you should see airlock activity within 8 to 24 hours. I am wondering if your fermentation is taking longer to start, if so I would consider #1 and #2 above.

Finally, yes shaking your fermenter may uncover yeast colonies that are trapped under the yeast cake and expose them to the fermentables, thus aiding in attenuation. However, the ZEN approach to brewing would suggest that the natural order of things should guide the fermentation process and not require such effort.
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Postby xxxx » Wed Jul 26, 2006 11:29 am

Thanks for your responses. Currently I don't "think" I have any problem aerating. Right now I have not used any aeration systems or stones primarily because of financial constraints and simplicity. When I transfer my wort, I also make sure to drop it in from very high up, and mix it well, and shake it for a good 20 minutes or so after adding the yeast. The temperature is always below 80.

I am an engineer however, and that drives me to want to best performance out of everything, especially my yeast :) That is why I thought about aerating throughout the primary. Take a look at this white labs yeast strain, and the associated instructions:

http://www.whitelabs.com/gravity.html

In order to attain the full attenuation, they aerate for 5 days. Naturally, this is a special case, but simply was curious to know if this could help for much simpler beers as well. Probably just as well to let the yeast do its own thing.
xxxx
 
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Postby billvelek » Fri Oct 27, 2006 8:28 pm

xxxx wrote:snip ... I thought about aerating throughout the primary. Take a look at this white labs yeast strain, and the associated instructions:

http://www.whitelabs.com/gravity.html

In order to attain the full attenuation, they aerate for 5 days. ... snip
I know this is a late response, but for what it's worth, this flys in the face of everything I have read about brewing. Stirring your yeast cake is one thing; adding air that will oxygenate your beer is another. I am stymied by whitelabs instructions. It is my understanding that the yeast reproduce during the aerobic phase, and _most_ alcohol is produced during the anaerobic stage -- (crabtree effect excepted) -- after the yeast have depleted all available oxygen. While aeration days later would probably reinvogorate the yeast, and start the aerobic process to produce new yeast as well, I don't know that those processes will consume the added oxygen fast enough to prevent the oxidation that will damage your beer. Just pitch an adequate starter of healthy yeast, and you won't need to take that chance. I don't know, but while Whitelabs might be experts on yeast, I'm beginning to wonder whether they know anything about beer. Either that, or an awful lot of brewers are dead wrong about oxidation.

Cheers.

Bill Velek
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