Author Topic: Right RPM for stir plate?  (Read 16832 times)

Offline denny

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Re: Right RPM for stir plate?
« Reply #60 on: January 14, 2015, 09:56:17 PM »
All I can tell ya is that I've tried almost exactly what's described above and I get much better and faster results with a stir plate.  Thank you for the theory, but I'm pragmatic.  I test different theories and do what works best for me in the real world.  As do you and all the rest of us.  All the theory in the world means nothing to me if my own practices produce better results.
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Offline Philbrew

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Re: Right RPM for stir plate?
« Reply #61 on: January 14, 2015, 10:10:34 PM »
" Unlike a stirred starter, a shaken starter that is pitched at high krausen does not taste, nor does it smell foul; hence, there is no need to decant other than the desire to avoid diluting one's wort.  The reason why a stirred starter smells so bad is that stirring fast enough to get any kind of gas exchange stresses the heck out of the cells.  Yeast produced odors and off-flavors are almost always a sign of stress."

S. cerevisiae,
You should go by James Bond 007.  Shaken not stirred, you wouldn't want to bruise the yeast. :-)

But what you said makes sense and I'll give it a try, though I may go to a 2L starter for lager.  Do you (or anyone) see a problem with filling the headspace in the starter vessel with welding O2 before the initial shake? 
Oh, and why the extra light DME?
Many of us would be on a strict liquid diet if it weren't for pretzels.

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Re: Right RPM for stir plate?
« Reply #62 on: January 14, 2015, 10:26:26 PM »
All I can tell ya is that I've tried almost exactly what's described above and I get much better and faster results with a stir plate.  Thank you for the theory, but I'm pragmatic.  I test different theories and do what works best for me in the real world.  As do you and all the rest of us.  All the theory in the world means nothing to me if my own practices produce better results.

The procedure that I proposed is not theory.  It's a practice that has stood the test of time.  If the procedure does not work for you, then you are performing a step differently because the results have been repeated by many people.

S. cerevisiae

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Re: Right RPM for stir plate?
« Reply #63 on: January 14, 2015, 10:34:29 PM »
Oh, and why the extra light DME?

Extra light DME usually contains a higher percentage of sugars that can be reduced to glucose by yeast cells than the darker DMEs.

Offline Philbrew

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Re: Right RPM for stir plate?
« Reply #64 on: January 15, 2015, 02:00:11 AM »
Oh, and why the extra light DME?

Extra light DME usually contains a higher percentage of sugars that can be reduced to glucose by yeast cells than the darker DMEs.
OK, thanks, I'll try that.
Any thoughts on the welding O2?  Increasing the percentage of O2 in the vessel headspace should help to get oxygen into the starter when shaken.  O2 is 20% of air so 1L of starter in a 1 gal. vessel gives 0.6 (approx.) volumes of O2 per volume of starter.  Increasing the O2 percentage in the headspace to 60% gives the same ratio of O2 volumes to starter volumes in 2L in a 1 gal. vessel.
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Offline Joe Sr.

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Re: Right RPM for stir plate?
« Reply #65 on: January 15, 2015, 02:04:27 AM »
Oh, and why the extra light DME?

Extra light DME usually contains a higher percentage of sugars that can be reduced to glucose by yeast cells than the darker DMEs.
OK, thanks, I'll try that.
Any thoughts on the welding O2?  Increasing the percentage of O2 in the vessel headspace should help to get oxygen into the starter when shaken.  O2 is 20% of air so 1L of starter in a 1 gal. vessel gives 0.6 (approx.) volumes of O2 per volume of starter.  Increasing the O2 percentage in the headspace to 60% gives the same ratio of O2 volumes to starter volumes in 2L in a 1 gal. vessel.

Don't overthink it.  My takeaway from this thread is that simple processes are just fine.

I will choose to stick with my stir plates.  Shake if you choose.  Pumping O2 into the headspace seems unnecessary.
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Offline Philbrew

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Re: Right RPM for stir plate?
« Reply #66 on: January 15, 2015, 02:17:14 AM »
"Don't overthink it.  My takeaway from this thread is that simple processes are just fine."

Overthinking is fun.  Under-thinking is fun too...if you've had enough beer!

Hmm...I may have found a sig line.
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Offline narcout

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Re: Right RPM for stir plate?
« Reply #67 on: January 15, 2015, 04:59:58 PM »
What's the right RPM for stir plate?

I turn mine up just enough so that the wort is rotating, which sometimes results in a small dimple on the surface.  To my eyes, this is less agitation than occurs in the fermentor during peak fermentation.

I used to not oxygenate my starters, I do now

I've started doing this as well.  How long of a blast of O2 are you hitting them with?
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S. cerevisiae

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Re: Right RPM for stir plate?
« Reply #68 on: January 15, 2015, 09:20:48 PM »
Any thoughts on the welding O2?  Increasing the percentage of O2 in the vessel headspace should help to get oxygen into the starter when shaken.  O2 is 20% of air so 1L of starter in a 1 gal. vessel gives 0.6 (approx.) volumes of O2 per volume of starter.  Increasing the O2 percentage in the headspace to 60% gives the same ratio of O2 volumes to starter volumes in 2L in a 1 gal. vessel.

If you want to inject O2, you should purchase 2 micron sintered stainless stone.   If you aerate the wort using a sterilized stone, you will not need to shake or have more head space than is necessary to keep the foam from coming out of the starter vessel.

S. cerevisiae

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Re: Right RPM for stir plate?
« Reply #69 on: January 15, 2015, 10:14:01 PM »
I was reading publications on suspension cell culturing last night, and they pretty much concurred with what I have written in this thread.  A stir speed that is fast enough to aerate the medium when using an Erlenmeyer flask and a magnetic stir bar results in shear force being placed on the cells.  In effect, a stir speed greater than 40 RPM can do more harm than good.   When using an Erlenmeyer flask and a magnetic stir bar, 40 RPM is not going to aerate wort without outside assistance.  We went to pitch happy, healthy yeast cells, not stressed out cells.

Now, those who insist on using a stir plate without forced aeration should seriously look into purchasing what is known as a "spinner flask" (price sensitive brewers should expect to experience major sticker shock if purchasing new).  There are two basic types of spinner flask.  One of the basic types has a suspended stir bar.  This type of spinner flask only agitates a culture, which does not make it much better than an Erlenmeyer flask with a magnetic stir bar.  The other basic type sports a vertical impeller.  That's the type that one wants when propagating yeast.  If possible, one wants to purchase a spinner flask where the impeller is tall enough that it sticks out of the wort, which will ensure adequate gas exchange at cell-friendly stir speeds.

Bar-Type Spinner Flask




Short Impeller-Type Spinner Flask



Tall Impeller-Type Spinner Flask







Offline Wort-H.O.G.

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Right RPM for stir plate?
« Reply #70 on: January 15, 2015, 10:50:08 PM »
cool thought. however i'm sure i'm not the only one who will say the following: many award winning, top quality, great tasting home brew beers have been made and will continue to be made with starters and stir plates...many of them i'd rate better than several commercial beers.  hows that song go..."must be doing something right".

at the end of the day, if what i make or what i drink tastes and smells like what I consider to be a good, great, or exceptional beer.... then in that, I trust.
« Last Edit: January 16, 2015, 12:47:23 AM by wort-h.o.g. »
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Offline jlevensailor

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Re: Right RPM for stir plate?
« Reply #71 on: January 16, 2015, 01:06:23 AM »
Correct me if i'm wrong
Yeast has 3 phases:
1. anaerobic - reproduce
2. aerobic - eat
3. cold - sleep

With this knowledge, it's better to keep a yeast starter barely covered to stop contamination, but allow breathing.
I've seen a lot of people use airlocks on their flasks

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S. cerevisiae

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Re: Right RPM for stir plate?
« Reply #72 on: January 16, 2015, 01:13:17 AM »
More award winning beers have been made without the aid of a stir plate than with one.   The wide use of a stir plate when making a starter is a relatively new thing.

I am not asking you to accept my method.  I am asking you to question your method because one stops growing as a brewer the moment that one stops questioning one's methods.  How many starters did you make before purchasing a stir plate?   How many side-by-side stir plate/non-stir plate tests have you conducted since purchasing a stir plate?   How do you personally know that a stir plate produces a healthier starter?

Like many, I initially accepted the claims made by those who were using stir plates to make yeast starters.  However, I had well over a decade of experience propagating almost every culture that I used from slant before starting to use a stir plate.  My results did not correlate with the claims being made by others.  Not only that, the claims being made by others did not align with science, which is why I spent six months making side-by-side comparisons before I came to the conclusion that some well meaning home brewer took the use of a stir plate in suspension cell culturing and blew it up into a must have when making a yeast starter.   

The reason why stir plates are used in suspension cell culturing is because it can be difficult to grow some cell lines because they want to clump together, which results in lower viable cell densities.  Continuous agitation helps to keep the cells in suspension.  The only place cell attachment is a problem when making a starter is when propagating extremely flocculent yeast strains.

Stir plates are not thing only half-baked science that has been preached as gospel to home brewers.  The same thing happened with yeast rinsing.  Some well-meaning home brewer took research that was performed by the ATCC back in the late eighties/early nineties involving the storage of small amounts of yeast cells under sterile water for extended periods of time and blew it up into the greatest yeast cropping and storage method since sliced bread.  The sad part is that the people promoting each process failed to understand the context in which the basic science was developed.  In the case of the ATCC research, the cultures were separated from all traces of nutrient via the use of a centrifuge before being stored under sterile water.  Boiled water cannot be assumed to be sterile because boiling does not kill spores.  Water has to be autoclaved to render it sterile, but the need to remove all traces of nutrient and use of truly sterile water fell by the wayside as the practice of rinsing yeast with and storing it under boiled water permeated the community.

Offline Wort-H.O.G.

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Re: Right RPM for stir plate?
« Reply #73 on: January 16, 2015, 01:24:25 AM »
We don't have to agree- that's the beauty of brewing. I'm very open to change- if it means it changes my finished product in a perceivable way....done it many times already and imagine it won't stop. But I can say that there's more than one way to make great beer- i truly believe that the more I brew and the more I see how different practices can produce the same results- great beer.
Ken- Chagrin Falls, OH
CPT, U.S.Army
https://www.facebook.com/pages/Harveys-Brewhaus/405092862905115

http://braukaiser.com/wiki/index.php?title=The_Science_of_Mashing

Serving:        In Process:
Vienna IPA          O'Fest
Dort
Mead                 
Cider                         
Ger'merican Blonde
Amber Ale
Next:
Ger Pils
O'Fest

Offline Philbrew

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Re: Right RPM for stir plate?
« Reply #74 on: January 16, 2015, 02:49:32 AM »
Any thoughts on the welding O2?  Increasing the percentage of O2 in the vessel headspace should help to get oxygen into the starter when shaken.  O2 is 20% of air so 1L of starter in a 1 gal. vessel gives 0.6 (approx.) volumes of O2 per volume of starter.  Increasing the O2 percentage in the headspace to 60% gives the same ratio of O2 volumes to starter volumes in 2L in a 1 gal. vessel.

If you want to inject O2, you should purchase 2 micron sintered stainless stone.   If you aerate the wort using a sterilized stone, you will not need to shake or have more head space than is necessary to keep the foam from coming out of the starter vessel.
Thanks S. cerv,
Much appreciate your (and everyone's) input.  I may get a 2 mc SS stone but your basic "shake it" approach appeals to my KISS side.
Many of us would be on a strict liquid diet if it weren't for pretzels.