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Old 11-21-2012, 04:30 PM   #1
BrewclearAssault
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Hey guys, my imagination was running wild again recently, this time through the fields of yeast starters, fermentation, and the combinations thereof.

A few batches ago, I started using yeast starters because I was told it was a great way to improve your beer. That held true. With my most recent batch, I assembled a stir plate that seems to have done it's job quite well, and I'm hoping for another jump up in quality for this batch.

My question though, is would using the stir plate during the primary fermentation multiply the yeast more and thus, give me even better beer? Or is this just wishful thinking?
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Old 11-21-2012, 04:45 PM   #2
billl
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Absolutely do NOT use the stir plate for your beer.

If you really want to see what it would do, take a 1/4 cup or so of the yeast cake when you finish this batch and make up another starter with it. Give it a couple days, chill, and decant the liquid into a glass. After 1 sip, I'm sure you'll never want to brew a whole batch that way.

 
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Old 11-21-2012, 04:45 PM   #3
jerrodm
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Sounds like fun--I'm imagining a stirplate that's maybe 20" across...on second thought, maybe a little too much fun.

However, if you want more yeast, the easier way would be to oxygenate (not simply aerate) your beer. Buy a wand and a tank of 02, and you'll get more yeast than you could ever hope to use.

 
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Old 11-21-2012, 04:46 PM   #4
BrewclearAssault
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Ah, that makes perfect sense. I was working off of the notion of "rousing" the yeast so that it doesn't settle so much. Thanks a lot!
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Old 11-21-2012, 04:49 PM   #5
BrewclearAssault
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Haha bill I'm gonna try that just for the hell of it, but I believe you! And I'll have to look into oxygenating my beer in the future, that sounds like a tempting idea.
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Old 11-21-2012, 07:16 PM   #6
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You will not oxygenate your fermenting beer with a stirplate....There is an incredible amount of CO2 being created. Some commercial operations have methods to keep the yeast in suspension Here during fermentation...they do their best work in suspension, not settled to the bottom.

A stirplate is used with starters to keep the yeast in suspension...there is no oxygen being absorbed into that starter with all the CO2 being pumped out.

Here is another abstract:
"...Much less intense mechanical agitation also decreases batch fermentation time for anaerobic beer production by about 25% compared to mixing by CO(2) evolution alone with a small change in the concentration of the different flavour compounds. These changes probably arise for two reasons. Firstly, the agitation increases the relative velocity and the area of contact between the cells and the wort, thereby enhancing the rate of mass transfer to and from the cells. Secondly, the agitation eliminates spatial variations in both yeast concentration and temperature, thus ensuring that the cells are maintained close to the optimum temperature profile during the whole of the fermentation time. These bench scale studies have recently been supported by results at the commercial scale from mixing by an impeller or by a rotary jet head, giving more consistent production without changes in final flavour. It is suggested that this reluctance of the brewing industry to use (adequate) mechanical agitation is another example where the myth of shear damage has had a detrimental effect on the optimal operation of commercial bioprocessing."

We would be better off if we had a means to keep the wort moving and the yeast in suspension...it's just difficult for the homebrewer and sanitation becomes the primary concern.
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Old 11-22-2012, 01:10 AM   #7
CryoEng
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Quote:
Originally Posted by helibrewer View Post
You will not oxygenate your fermenting beer with a stirplate....There is an incredible amount of CO2 being created. Some commercial operations have methods to keep the yeast in suspension Here during fermentation...they do their best work in suspension, not settled to the bottom.

A stirplate is used with starters to keep the yeast in suspension...there is no oxygen being absorbed into that starter with all the CO2 being pumped out.
Yes! And, in absolute fact, oxygen is never actually good during our processes.

Oxygenation is never a positive for the wort.

Yeast need the O2 to produce some fatty acids so they can reproduce, but we sacrifice the O2 combining with everything else in our wort to make the yeast happy.

It's a trade. MORE O2 is not the goal. That's bad. Enough O2 is better, but no O2 and another supply of fatty acids would be better. Hence the efforts to use other sources (olive oil, etc).

Cheers

 
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Old 11-22-2012, 02:11 AM   #8
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Quote:
Originally Posted by helibrewer View Post
You will not oxygenate your fermenting beer with a stirplate....There is an incredible amount of CO2 being created. Some commercial operations have methods to keep the yeast in suspension Here during fermentation...they do their best work in suspension, not settled to the bottom.
A few years ago I became interested in such reports and decided to try it out on a small scale. I made a stir plate large enough to agitate a 6 gal carboy as long as fermentation was taking place. In my experience, the fermentation is shorter and more consistent between batches than what I was getting before agitation. here's my rig...


Cheers..

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Old 11-23-2012, 05:54 PM   #9
jerrodm
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That is sweet. Just make sure you keep it away from your teenage daughters...

 
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Old 11-27-2012, 05:06 PM   #10

Quote:
Originally Posted by helibrewer View Post
You will not oxygenate your fermenting beer with a stirplate....There is an incredible amount of CO2 being created. Some commercial operations have methods to keep the yeast in suspension Here during fermentation...they do their best work in suspension, not settled to the bottom.

A stirplate is used with starters to keep the yeast in suspension...there is no oxygen being absorbed into that starter with all the CO2 being pumped out.

Here is another abstract:
"...Much less intense mechanical agitation also decreases batch fermentation time for anaerobic beer production by about 25% compared to mixing by CO(2) evolution alone with a small change in the concentration of the different flavour compounds. These changes probably arise for two reasons. Firstly, the agitation increases the relative velocity and the area of contact between the cells and the wort, thereby enhancing the rate of mass transfer to and from the cells. Secondly, the agitation eliminates spatial variations in both yeast concentration and temperature, thus ensuring that the cells are maintained close to the optimum temperature profile during the whole of the fermentation time. These bench scale studies have recently been supported by results at the commercial scale from mixing by an impeller or by a rotary jet head, giving more consistent production without changes in final flavour. It is suggested that this reluctance of the brewing industry to use (adequate) mechanical agitation is another example where the myth of shear damage has had a detrimental effect on the optimal operation of commercial bioprocessing."

We would be better off if we had a means to keep the wort moving and the yeast in suspension...it's just difficult for the homebrewer and sanitation becomes the primary concern.
Great post; thanks for the info.
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