[Big Monk]

I am not a scientist, but I don't think you need to count cells to know that there is a significant difference between pitching a full yeast cake from a previous batch and pitching a smack pack.

I'm not crapping on the science, but I think that when you're dealing with orders of magnitude scientific precision may not always be needed.  Also, when you're talking about repeated results (over pitch, lower esters) across a span of years and many different brewers it's fair to question what's going on when results appear to differ from the science.

We're all speculating here anyway.

Right. I’ve always followed the train of thought that ester production is INVERSELY related to yeast growth. So if I’m after ester synthesis that is the keystone. All other levers must revolve around that.

I agree with you but I was also trying to respond to one of Dave’s original comments that this science needed some testing. It’s less about homebrewers being precise (unless they want to be) and more about knowing the science is settled and ready for use in your brewery.

[Joe Sr.]

Gotcha. I'm sure the science is sound. Now to control for all of the unknown variables.

[klickitat jim]

Growth of a home brewer
Day 1: Does the yeast go in before or after the boil?
Day 2: What is the best lab to get my pre and post fermentation FAN analyzed?
Day 3: Wish I had time to brew

[hopfenundmalz]

I will throw out there that it might not be a monotonic function, but it could be like an upside down parabola.

Low pitch rates give high esters.
Optimum pitch rates give low esters.
High pitch rates give high esters.

[klickitat jim]

And maybe not...
Pitching 1 smack pack, active starters, to any ale I've done so far from 1.050 to 1.110, with numerous yeasts from American to English, I don't find any beer "estery"

One constant I find in home brewing. We read things and therefore they are so, even though we can't make it happen at home.

[Big Monk]

And maybe not...
Pitching 1 smack pack, active starters, to any ale I've done so far from 1.050 to 1.110, with numerous yeasts from American to English, I don't find any beer "estery"

One constant I find in home brewing. We read things and therefore they are so, even though we can't make it happen at home.

I really only pay attention to the science when known ester and higher alcohol producers like Belgian yeast is concerned. There I see results when I play with the levers.

[klickitat jim]

I think Belgian yeasts play by different rules, not just than other ales or lagers, but sometimes different than other Belgians

[klickitat jim]

If it were up to me to classify yeast, it wiuld be Ale, Lager, Hybrid, Belgian, and Wild

[joelv]

You have


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[Robert]

If it were up to me to classify yeast, it wiuld be Ale, Lager, Hybrid, Belgian, and Wild

And if it were up to me, those  classifications would ignore genotype.   And top/bottom behavior and much else related to phenotype.  Just, what does the beer it makes taste like?  Clean, fruity, funky...?  That's how I'd classify  beer itself.  What it's like, not how it's made.  And if you can manipulate the same yeast to get different characters in the beer, hmm, things get even simpler.  Unless you're all OCD about taxonomy.

[Wilbur]

Really interesting to read this with regards to Lars Garshol's post on using Kveik. Probably need to read through both to really get it, but he recommended underpitching to suppress esters in kveik.

http://www.garshol.priv.no/blog/393.html

[Robert]

Back in 2003, the Homebrew Digest ran "A Fortnight of Yeast", where you could ask questions of Dr. Clayton Cone, head of Lallemand and inventor of Fermaid K.  Here's the question I asked and Dr. Cone's response....

"Dr. Cone,
   First, thank you so much for giving us some of your time.
   My question concerns yeast growth as it relates to flavors in beer.  I
have read several articles mentioning that yeast growth is important to
flavor production in beer, and that the amount of yeast growth is related to
the amount of yeast pitched.  My own completely unscientific experiments
have
lead  me to believe that I produce more "interesting' beers when I, for
instance, repitch only part of the yeast slurry from a previous batch
rather than the entire amount.  The conventional wisdom in the homebrew
world seems to be to use the entire previous slurry to produce short lag
times.  Is there a relationship between yeast growth and the flavors
produced in beer?  Is it better to pitch an entire previous yeast slurry,
or is there a benefit to using a large, but not entire, amount of
slurry?  I apologize for the vagueness of the question, but I have no way
to quantify the exact amounts I've been using.  It's simply either "all" or
"part".
   Thank you again.
Denny Conn


Denny Conn,
   Ester and other flavor component production or synthesis is a complex
subject because there are so many variables taking place at the same time.
   You are right, ester production is related to yeast growth but not in the
way you might think. The key element to yeast growth and ester production is
acyl Co-A. It is necessary for both yeast growth and ester production.  When
it is busy with yeast growth, during the early part of the fermentation, it
is not available for ester production.  Ester production is directly related
to biomass production. Everything that increases biomass production
(intensive aeration, sufficient amount of unsaturated fatty acids,
stirring) decreases ester production. The more biomass that is produced the
more Co-enzyme A is used and therefore not available for ester production.
Anything that inhibits or slows down yeast growth usually causes an increase
in ester production: low nutrient, low O2.  It has been noted that a drop in
available O2 from 8 ppm down to 3 ppm can cause a four fold increase in
esters.
   Stirring in normal gravity decreases ester production. Stirring in high
gravity increases ester production. CO2 pressure in early fermentation
decreases ester production.  Taller fermenters produce less esters than
short fermenters. High temperature early in fermentation decreases ester
production.  High temperature later in fermentation increases ester
production. Low pitching rate can result in less esters.
   There are other flavor components such as higher alcohol that have there
own
set of variables. Stirring increases production of higher alcohols.  CO2
pressure does not effect the production of alcohol. Amino acid levels in the
wort effect the production of higher alcohols.  Most of the higher alcohol
is produced during the growth phase (exponential phase) of the yeast.
   I am sure that there are many other variables.  I am also sure that there
are beer makers that have experienced the very opposite with each of the
variables.

   Pitching rates depend on several factors:
   (1) The speed in which you wish the fermentation to take place.  Some
professional brew master are in more of a hurry than others; desired beer
style, shortage of fermenter space.  Pitching rates would vary as a means to
increase or decrease the total fermentation time. 10 X 10/6th cell
population for normal fermentation rates.  20 X 10/6th or more for a quick
turn around.
   (2) Temperature control.  If lack of refrigeration is a problem, the
fermentation needs to be spread out over a longer period  by pitching with
less yeast.
   (3) Health of the pitching yeast. If the pitching yeast has not been
stored
under ideal conditions (4C for less than one week) then larger pitching rate
must be done to compensate for the deteriorate of the yeast.  Increased
pitching rates has its limits in trying to compensate for poor storage
conditions.
   (4) When all other variables are under control you can use variations in
pitching rates to achieve certain flavor profile that are of interest to
you.
   Conventional wisdom regarding pitching rate can lead to problems.  During
each fermentation cycle the yeast will increase in size about three times,
so if you use all the yeast from the previous batch you will soon be
pitching with a huge amount of yeast.  Professional brewers usually re-pitch
with about 25% of the yeast from the previous batch.
   Proper handling of the yeast during storage (4C and <7 days) will
minimize
any problem with long lag phase. Start with a fresh culture of yeast after
about five recycles for bacteria control and or after 10 - 15 cycles for
genetic drift purposes.
   There are many who will say that they are proud of the fact that they
have
used the same yeast after over 100 cycles.  More power to them. I wish that
I could explain their luck. Good practices suggest frequent renewal with a
fresh culture is a good policy.
   Thank you for your very good question.

Clayton Cone"

OK, so I've always taken that to mean that pitching "too much" yeast means that there is less biomass production and consequently more esters.  That's pretty much the opposite of the conventional wisdom, as MANY people have pointed out to me over the years.  So, I want to know how you interpret this.  Am I right?  Or am I totally missing something that confirms the conventional wisdom?

Don't really mean to raise a zombie thread,  but I remembered this and came back to read it through in context of my experiments and research in pressurized fermentation.    Pressure early on is held to suppress yeast growth, which Dr. Cone suggests should increase esters, while reduction of ester production is a primary goal of pressure fermentation.   Dr. Cone, nonetheless, says that pressure early on does suppress ester formation.  There seems to be some tension here.  Further, research seems to indicate that it is pressure later in fermentation that somehow suppresses ester formation. Perhaps this is connected with increased yeast growth if pressure is not applied early, I don't know.  Then what is the mechanism  of ester formation after the log phase that pressure is suppressing? I still don't know what any of this means,  but find it interesting and thought the evidence from pressure fermentation should be thrown on the pile.