Author Topic: Right RPM for stir plate?  (Read 16802 times)

Offline duboman

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Re: Right RPM for stir plate?
« Reply #45 on: January 13, 2015, 08:17:36 PM »
No, what I am saying is that having to start ale fermentations in the high 50s/low 60s in order to avoid off-flavors is a sign that there is something in the fermentation other than the pitched ale strain. Few ale strains require low sixties fermentation temperatures in order to produce their specified fermentation by-product profile.  Most of the non-specialty ale strains that are available home brewers do not start to misbehave in a major way until fermentation temperatures are well into the seventies if they are not stressed and wort composition is sound.

But that doesn't account for personal taste.  I don't start low because I get "bad" flavors from starting higher.  I do it because I prefer the flavor profile I get from fermenting at lower temps.  I'm afraid your scientific analysis doesn't take that into account.
My thought as well. I feel that there is more to this whole conversation than the specific science/microbiology involved
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Offline HoosierBrew

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Re: Right RPM for stir plate?
« Reply #46 on: January 13, 2015, 08:19:17 PM »
No, what I am saying is that having to start ale fermentations in the high 50s/low 60s in order to avoid off-flavors is a sign that there is something in the fermentation other than the pitched ale strain. Few ale strains require low sixties fermentation temperatures in order to produce their specified fermentation by-product profile.  Most of the non-specialty ale strains that are available home brewers do not start to misbehave in a major way until fermentation temperatures are well into the seventies if they are not stressed and wort composition is sound.

But that doesn't account for personal taste.  I don't start low because I get "bad" flavors from starting higher.  I do it because I prefer the flavor profile I get from fermenting at lower temps.  I'm afraid your scientific analysis doesn't take that into account.
My thought as well. I feel that there is more to this whole conversation than the specific science/microbiology involved

+2.  I feel the same.
Jon H.

S. cerevisiae

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Re: Right RPM for stir plate?
« Reply #47 on: January 13, 2015, 10:23:10 PM »
But that doesn't account for personal taste.  I don't start low because I get "bad" flavors from starting higher.  I do it because I prefer the flavor profile I get from fermenting at lower temps.  I'm afraid your scientific analysis doesn't take that into account.

However, that's not how low temperature ale fermentation or temperature ramped fermentation is presented in this forum and others.  It's presented as a requirement for quality ale production.  A temperature-controlled fermentation chamber is one of the first things that I see promoted when a new brewer asks about gear and/or process improvement even though the brewer is fermenting ale.  No one even bothers to ask what the ambient temperature is in the brewer's fermentation room before offering the suggestion.  It's all about using refrigeration for a process that can be performed in the high sixties/low seventies range with excellent results, a temperature range that is easily met for most of the year in below grade basements in states that experience four seasons. The trick is picking the right yeast culture for the task at hand, not tricking the yeast culture into performing the task at hand.  Those who live in warm states have no choice, but to resort to forced attemperation.
« Last Edit: January 14, 2015, 12:54:09 AM by S. cerevisiae »

Offline Joe Sr.

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Re: Right RPM for stir plate?
« Reply #48 on: January 13, 2015, 10:54:41 PM »
I can agree that temp control tends to be over emphasized.  You do not need a fermentation fridge to make good beer.  You can make perfectly good beer at ambient temps, assuming your ambient temps are within the right range (I'd say not higher than 68) and that they remain stable.  I don't think it's best practice to ferment your ales in the 70s, though I've had that happen on occasion, but you can certainly make drinkable beer, even good beer if you've got a strain that can handle those temps.

I've seen newer brewers on this forum get worried about having to dump a beer because fermentation temps got into the 70s, without yet having tasted the beer.  That's no the relax, don't worry approach.

As a group, we tend to get obsessive about things and I think that keeping things simple is the best way for new brewers to get going.  Not everyone needs all the tricked out gadgets.  Not everyone needs a dedicated fermentation fridge.

However, I do think it's important for brewers to understand fermentation temperatures and the impact/effect of different temperatures.  Figure out what works for you and what you like.  I think we're all interested in obtaining consistent results and fermentation temperature control is important for consistent results (even if your temp control is simply a consistent ambient temp).

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Offline erockrph

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Re: Right RPM for stir plate?
« Reply #49 on: January 13, 2015, 11:55:05 PM »
But that doesn't account for personal taste.  I don't start low because I get "bad" flavors from starting higher.  I do it because I prefer the flavor profile I get from fermenting at lower temps.  I'm afraid your scientific analysis doesn't take that into account.

However, that's not how low temperature ale fermentation or temperature ramped fermentation is presented in this forum and others.  It's presented as a requirement for quality ale production.  A temperature-controlled fermentation chamber is one of the first things that I see promoted when a new brewer asks about gear and/or process improvement even though the brewer is fermenting ale.  No one even bothers to ask what the ambient temperature is in the brewer's fermentation room before offering the suggestion.  It's all about using refrigeration for a process that can be performed in the high sixties/low seventies range with excellent results, a temperature range that is easy met for most of the year in below grade basements in states that experience four seasons. The trick is picking the right yeast culture for the task at hand, not tricking the yeast culture into performing the task at hand.  Those who live in warm states have no choice, but to resort to forced attemperation.

I will say that I believe pitching an appropriately-sized, healthy pitch of yeast is at least as important (if not more) than keeping your pitching temperature low. Outside of certain ale strains that produce a significant amount of flavor compounds (hefe strains and some [but not all] abbey-style strains), I get damn near the same result from most ale strains at the full range of ambient fermentation temps in my basement - regardless of whether that is 58F or 66F.
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Offline narcout

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Re: Right RPM for stir plate?
« Reply #50 on: January 14, 2015, 05:03:56 AM »
the maximum cell densities for 1L and 2L starters are 200 billion cells and 400 billion cells respectively

I wonder how close I am actually getting to those maximum cell densities. 

In the experiment discussed on page 140 of Yeast, when 100 billion cells were pitched into 2 liters of 1.036 wort at 70 degrees, the total cells after the starter was complete were only 205 billion.

When 100 billion cells were pitched into 4 liters of the same wort, the total cells after the starter was complete were only 276 billion. 

White and Zainasheff note that no oxygen was added and that the starters were not agitated.  I think they would have grown more cells had they done either of those things but how many more I have no idea.
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Re: Right RPM for stir plate?
« Reply #51 on: January 14, 2015, 06:09:50 PM »
Two hundred billion cells is the theoretical maximum number of cells that can live in 1L of a liquid medium.  It does not mean that a 1L starter will automatically produce 200 billion cells.  The amount of extract and the average size of the yeast cells in the starter also play a role in the total cell count.  If I recall correctly, DeClerk stated that 1 gram of extract is required to produce 1 billion cells.  Whether or not that claim holds is an exercise unto itself.  Assuming that DeClerck is correct, we would need have 100 grams of DME in a 1L starter in order to grow 100 billion cells.   That's a specific gravity of 1.040.   As you have already mentioned, available oxygen plays a vital role because the ergosterol and UFAs that are synthesized while O2 is still in solution are shared with all of the daughter cells.  These compounds are vital to cell health because they make cell membranes more pliable, which, in turn, makes it easier to pass nutrients and waste products in and out of the cells.

In the end, here's something that really needs to be driven home.  Starters a little like nuclear weapons in that close enough gets the job done.  Cell population growth is exponential, not linear.   Hence, the difference between 200 billion cells and 400 billions cell is roughly one reproduction period, and the difference between 200 billion cells and 800 billion cells is roughly two replication periods.  Dissolved O2, the amount of carbon (extract), and volume of the liquid medium all play a role in replication.   The best thing that we can do as brewers is to ensure that the cells that we pitch are healthy because healthy cells reproduce.   The other thing that need to do is to ensure that we aerate our wort because healthy cells can become unhealthy cells without adequate aeration.
« Last Edit: October 02, 2015, 07:03:34 PM by S. cerevisiae »

Offline Stevie

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Re: Right RPM for stir plate?
« Reply #52 on: January 14, 2015, 06:12:07 PM »
So without using a microscope, you just make a starter of N to get N x 100B cells?

Offline narcout

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Re: Right RPM for stir plate?
« Reply #53 on: January 14, 2015, 06:52:22 PM »
Starters a little like nuclear weapons in that close enough gets the job done.

Agree.

Cell population growth is exponential, not linear.   Hence, the difference between 200 billion cells and 400 billions cell is roughly one reproduction period, and the difference between 200 billion cells and 800 billion cells is roughly two replication periods.  Dissolved O2, the amount of carbon (extract), and volume of the liquid medium all play a role in replication.

I take your point, but as you note (and as is shown in Yeast) there are factors which affect the number of reproduction periods that will be obtained.  Also, as I think you've referenced before, the amount of cell reproduction has flavor implications.

Anyway, I'm making a starter tomorrow night for a dunkel I will brew on Friday night and pitch Saturday morning.  I'm going to attempt to cold crash the starter at the end of the exponential phase rather than waiting for it to ferment out (if I make it home from work in time Friday afternoon).  I'll be curious to see if the supernatant, as you call it, tastes any different than usual.
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Offline Wort-H.O.G.

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Re: Right RPM for stir plate?
« Reply #54 on: January 14, 2015, 06:58:31 PM »
non scientific but i can say that when i made a lager starter less than 1-gal on stir plate fully fermented, i had off flavors to deal with that didn't always clean up with d-rest and lagering. when i made a 3.8-4L starter on a stir plate and fully fermented, my lagers were extremely clean and ready to drink at the 3-4 weeks mark.

Conclusion: right amount of healthy yeast gets the job done with good results...enough science for me without really knowing cell counts...just targets
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Offline Philbrew

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Re: Right RPM for stir plate?
« Reply #55 on: January 14, 2015, 07:26:30 PM »
non scientific but i can say that when i made a lager starter less than 1-gal on stir plate fully fermented, i had off flavors to deal with that didn't always clean up with d-rest and lagering. when i made a 3.8-4L starter on a stir plate and fully fermented, my lagers were extremely clean and ready to drink at the 3-4 weeks mark.

Conclusion: right amount of healthy yeast gets the job done with good results...enough science for me without really knowing cell counts...just targets
How did you do a 3.8-4L starter on a stir plate?  Do I need a heavy duty stir plate?  What vessel did you use?  Can I use a 1 gal. glass jar with a flat bottom?
In the less-than-1 gal. and also the 4L did you decant the beer and pitch the slurry or did you pitch the whole starter?
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Re: Right RPM for stir plate?
« Reply #56 on: January 14, 2015, 07:41:33 PM »
non scientific but i can say that when i made a lager starter less than 1-gal on stir plate fully fermented, i had off flavors to deal with that didn't always clean up with d-rest and lagering. when i made a 3.8-4L starter on a stir plate and fully fermented, my lagers were extremely clean and ready to drink at the 3-4 weeks mark.

Something does not sound right.  I have fermented normal gravity 5.5-gallon batches with as little as a 1L starter without off-flavors.   What kinds of off-flavors do you have?  How much head space did you have in the starter vessel?  Initial dissolved O2 level is more critical than continuous stirring.  All continuous stirring does is keep the cells from dropping out of suspension prematurely.


Offline Wort-H.O.G.

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Re: Right RPM for stir plate?
« Reply #57 on: January 14, 2015, 07:45:36 PM »

non scientific but i can say that when i made a lager starter less than 1-gal on stir plate fully fermented, i had off flavors to deal with that didn't always clean up with d-rest and lagering. when i made a 3.8-4L starter on a stir plate and fully fermented, my lagers were extremely clean and ready to drink at the 3-4 weeks mark.

Conclusion: right amount of healthy yeast gets the job done with good results...enough science for me without really knowing cell counts...just targets
How did you do a 3.8-4L starter on a stir plate?  Do I need a heavy duty stir plate?  What vessel did you use?  Can I use a 1 gal. glass jar with a flat bottom?
In the less-than-1 gal. and also the 4L did you decant the beer and pitch the slurry or did you pitch the whole starter?
I have larger stir plate and 5L flask. I do decant -always.  You can use whatever works on your stir plate.
Ken- Chagrin Falls, OH
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Offline Wort-H.O.G.

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Re: Right RPM for stir plate?
« Reply #58 on: January 14, 2015, 07:47:34 PM »

non scientific but i can say that when i made a lager starter less than 1-gal on stir plate fully fermented, i had off flavors to deal with that didn't always clean up with d-rest and lagering. when i made a 3.8-4L starter on a stir plate and fully fermented, my lagers were extremely clean and ready to drink at the 3-4 weeks mark.

Something does not sound right.  I have fermented normal gravity 5.5-gallon batches with as little as a 1L starter without off-flavors.   What kinds of off-flavors do you have?  How much head space did you have in the starter vessel?  Initial dissolved O2 level is more critical than continuous stirring.  All continuous stirring does is keep the cells from dropping out of suspension prematurely.
Talking lagers here. 1L starter wouldn't cut it IME. Also talking about negative aspects of unhealthy, stressed yeast and their contributions to the beer.
Ken- Chagrin Falls, OH
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https://www.facebook.com/pages/Harveys-Brewhaus/405092862905115

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

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« Reply #59 on: January 14, 2015, 08:40:21 PM »
Talking lagers here. 1L starter wouldn't cut it IME. Also talking about negative aspects of unhealthy, stressed yeast and their contributions to the beer.

Yes, a 1L starter will cut it if grown correctly and pitched at the correct time.

In my humble opinion, stir plates are the brewing snake oil of the twenty-first century.  They were introduced to brewing by scientists involved in suspension cell culture (primarily cancer research).  Clumping is a problem in suspension cell culture.  The purpose of using a stir plate in cell culture is to prevent clumping.  It does not aerate as home brewers have been led to believe, especially when the media in the stirred vessel consumes more than 1/3rd of the internal volume.

Here's a test that you can run if you do not believe me.  Prepare 1L of 1.040 (10%) wort like you would when making a stirred starter (use extra light DME).  Chill and pour the media into a sanitized 1-gallon jug using a sanitized funnel if necessary (alternatively, you can pour the media into a sanitized 1-gallon jug hot and let it cool, but you will need to warm the jug first to prevent stress fractures).  After the media has been cooled and transferred to the jug, remove the cap from the White Labs vial, take a cotton swab that has been soaked with 91% isopropyl alcohol, and lightly wipe the surface of the lip of the vial over which the culture will be poured (try to avoid having alcohol run down the sides of the vial).  After waiting about thirty seconds, take a lighter and quickly pass the pouring lip through the flame (alternatively, move the lighter instead of the vial).  You will need to make quick passes in order to avoid melting the vial.   Now, quickly pour the yeast culture into the jug after flaming the lip of the vial, and screw on a sanitized plastic 1-gallon jug replacement cap (most home brewing supply store sell these caps).  Do not use a paper lined cap.  After the cap has been screwed on, shake the jug until the media is almost all foam.   All you need to do from this point forward is loosen the cap after the foam settles down and wait until high krausen, which should occur within 12 to 18 hours (often sooner).   Pitch the entire contents of the jug after high krausen has been reached using the same basic aseptic transfer technique that was performed with the White Labs vial (i.e., wipe and flame the lip of the jug before pitching its contents).  You will need to ensure that your wort is well aerated.

I guarantee that a 1L starter grown this way will fully attenuate a 5-gallon batch of lager at lager fermentation temperatures without producing off-flavors (a 2L starter will reduce O2 requirements and the exponential phase slightly).  In fact, I guarantee that is works as well, if not better than a much larger volume starter that is grown on a stir plate the way that most home brewers make starters on a stir plate.  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.
« Last Edit: January 14, 2015, 08:46:20 PM by S. cerevisiae »