Can we address the dry yeast yeast starter concept again?

[schematix]

Obviously your opinions on brulosophy are well known and probably why I went there....but it’s interesting, at least to me, that Marshall is a committed starter guy, but can’t manage to show the value.

I don't need a crowd of other people to tell me what estery, phenolic, under attenuated oxidized beer tastes like. I can sense it myself, i don't like it, and know how to solve it.

 

[Silver_Is_Money]

Due to truth in advertising laws, the reported cell counts for yeast packages (dry or liquid) are highly likely to be minimums, which may potentially grossly under-report the typical count of active/live yeast present.

 

[Big Monk]

I NEVER make a starter. There, I said it. Been brewing for 13 years. My beers taste good.

Due to truth in advertising laws, the reported cell counts for yeast packages (dry or liquid) are highly likely to be minimums, which may potentially grossly under-report the typical count of active/live yeast present.

I doubt that. Count them and see. I bet you’d get counts consistent with viability dating.

 

[BrewnWKopperKat]

Many of the things "most of us know" seem to shift over time and turns out we didn't really know them all that well at all. In this case I think it is possible that the quality of liquid yeast has changed over time and what we all knew to be true five years ago may not exactly apply today.

(emphasis added for those who skim)

This ('many of the things "most of us know" seem to shift over time') will likely continue as new information from presentations ("BYO Boot Camps" and "Hop and Brew School") and newer books ("The New IPA", "Simple Homebrewing") continue to filter into homebrewing forums. The "Hop and Brew School" reference is off topic - but the referenced data/science suggests that one doesn't need to vacuum seal hops when putting them in the freezer (it's up to you to trust or ignore the data). For dry yeast, presentations on E2U with more summary data are starting to appear (sorry, no direct links on this one: try a Google search for PDFs from likely presenters).

 

[mongoose33]

Obviously your opinions on brulosophy are well known and probably why I went there....but it’s interesting, at least to me, that Marshall is a committed starter guy, but can’t manage to show the value.

I think there's value that doesn't necessarily show up every time in flavors, in that it's insurance. You've probably seen me say this before, but I'll repeat it for others. My son is a microbiologist and also a home brewer. He says virtually all homebrews are "infected" in that there's dust and stuff floating in the air that ends up in our wort. Dust has bacteria on it, if we cough we expel droplets that contain bacteria, things like that.

If there's enough of those nasties in there, they can get a foothold and create off-flavors, and since bacteria reproduces far faster than yeast, it can happen fast.

A starter, by virtue of getting more yeast cells in the wort, and (in my case) taking off much faster than normal, allows the yeast the opportunity to outcompete any nasties that have fallen into the wort.

So--arguably there's value in doing a starter for that reason. Many brewers might argue that they don't have those off flavors even though they don't do a starter, but that doesn't mean they don't, at least occasionally. There isn't enough crap falling into our wort all the time to make a difference, time of year probably matters (bacteria-laden pollen, e.g.), it may not be bacteria that produces off-flavors of significance, and frankly, I'm skeptical of many brewers' ability to detect those off-flavors anyway. *see below for more on this

***

I met Marshall at the BYO boot camp in Asheville. Three things stood out. 1) Nice guy, enjoyed the chance to visit with him the first night. 2) He looks younger in person than pics I've seen of him. 3) He had a glass of my Darth Lager, and when it was done, said "Let me have some more of that." Highlight of my trip.

***

My skepticism of the Brulosophy approach is fairly well-known here, I think. They just don't control the tasting panels adequately for me to have confidence in the results. There's no control over what people are drinking prior to doing the tasting, and if they're burning their taste buds with IPAs before testing, or eating spicy or aromatic foods (garlic!), is it that they can't detect a difference, or that there's no difference? They also don't do the triangle test correctly--the orders in which people are exposed to the beers is supposed to be randomized, to eliminate ordering effects.

I did an experiment like this, and it's hard to do it. Participants don't care as much, there's all this stuff to keep organized, it's hard to get people to do the test before they start destroying their palate with all the various and sundry homebrews brought for trying....so it's not like I'm saying it's easy to do this all according to Hoyle. It's not.

That said, at least they're trying something. "Man in the arena" kind of thing. I think the control they bring to the two-batch approach is actually quite good. I'm a scientist, they really do a nice job trying to isolate the experimental variable each time.

***

* I'm pretty skeptical of a single anecdotal claim of something regarding taste or off-flavors. There's lots of evidence that people have different palates, that some flavors (off-flavor or otherwise) are not perceptible to some people, and so on. All you need to do is see the results of judging competitions; I've seen where people submit the exact same beer under two different entries; one wins or medals, the other is panned as bad. Same beer.

I've entered beer in local comps, only to be stunned with what won the competition. Off-flavor in the beer, either extract twang or something else, whereas mine did not have that. (yeah, sour grapes here ). A buddy and I were at one of these, where the beer being judged was an Amber. I've got a pretty good one. We were shocked at what won, as if I'd had a sample of it at a taproom, I'd have never ordered a full glass. Nor my buddy, either.

I've done an off-flavor workshop, and I've become better at identifying off-flavors, though often pinpointing the source for me can be difficult. None of the judges at these comps have, as far as I can tell, ever done that.

So--when people say they don't have an off-flavor in a beer, I take it with a grain of salt. Is it because, THIS TIME, it wasn't infected, but next time it might be? Or that they can't detect an off-flavor that others would? A single anecdotal account is only that. Now, this doesn't mean I think the person is lying, I don't. It's just that it's a one-off judgment.

What I will do is take such a claim as a working hypothesis, looking for evidence it's wrong (which is all you can do in science). I'll also gather evidence that supports it, and eventually, if it looks interesting, I might do it in my own beer. That's what I did with pitching the single pack of White Labs yeast, no starter. White said he'd do that, my son has done it several times with no apparent ill-effects, and I just did it producing an excellent beer.

You reading this can take that as anecdotal, because....that's what it is.

 

[Gregory T]

I think there's value that doesn't necessarily show up every time in flavors, in that it's insurance. You've probably seen me say this before, but I'll repeat it for others. My son is a microbiologist and also a home brewer. He says virtually all homebrews are "infected" in that there's dust and stuff floating in the air that ends up in our wort. Dust has bacteria on it, if we cough we expel droplets that contain bacteria, things like that.

If there's enough of those nasties in there, they can get a foothold and create off-flavors, and since bacteria reproduces far faster than yeast, it can happen fast.

A starter, by virtue of getting more yeast cells in the wort, and (in my case) taking off much faster than normal, allows the yeast the opportunity to outcompete any nasties that have fallen into the wort.

So--arguably there's value in doing a starter for that reason. Many brewers might argue that they don't have those off flavors even though they don't do a starter, but that doesn't mean they don't, at least occasionally. There isn't enough crap falling into our wort all the time to make a difference, time of year probably matters (bacteria-laden pollen, e.g.), it may not be bacteria that produces off-flavors of significance, and frankly, I'm skeptical of many brewers' ability to detect those off-flavors anyway. *see below for more on this

***

I met Marshall at the BYO boot camp in Asheville. Three things stood out. 1) Nice guy, enjoyed the chance to visit with him the first night. 2) He looks younger in person than pics I've seen of him. 3) He had a glass of my Darth Lager, and when it was done, said "Let me have some more of that." Highlight of my trip.

***

My skepticism of the Brulosophy approach is fairly well-known here, I think. They just don't control the tasting panels adequately for me to have confidence in the results. There's no control over what people are drinking prior to doing the tasting, and if they're burning their taste buds with IPAs before testing, or eating spicy or aromatic foods (garlic!), is it that they can't detect a difference, or that there's no difference? They also don't do the triangle test correctly--the orders in which people are exposed to the beers is supposed to be randomized, to eliminate ordering effects.

I did an experiment like this, and it's hard to do it. Participants don't care as much, there's all this stuff to keep organized, it's hard to get people to do the test before they start destroying their palate with all the various and sundry homebrews brought for trying....so it's not like I'm saying it's easy to do this all according to Hoyle. It's not.

That said, at least they're trying something. "Man in the arena" kind of thing. I think the control they bring to the two-batch approach is actually quite good. I'm a scientist, they really do a nice job trying to isolate the experimental variable each time.

***

* I'm pretty skeptical of a single anecdotal claim of something regarding taste or off-flavors. There's lots of evidence that people have different palates, that some flavors (off-flavor or otherwise) are not perceptible to some people, and so on. All you need to do is see the results of judging competitions; I've seen where people submit the exact same beer under two different entries; one wins or medals, the other is panned as bad. Same beer.

I've entered beer in local comps, only to be stunned with what won the competition. Off-flavor in the beer, either extract twang or something else, whereas mine did not have that. (yeah, sour grapes here ). A buddy and I were at one of these, where the beer being judged was an Amber. I've got a pretty good one. We were shocked at what won, as if I'd had a sample of it at a taproom, I'd have never ordered a full glass. Nor my buddy, either.

I've done an off-flavor workshop, and I've become better at identifying off-flavors, though often pinpointing the source for me can be difficult. None of the judges at these comps have, as far as I can tell, ever done that.

So--when people say they don't have an off-flavor in a beer, I take it with a grain of salt. Is it because, THIS TIME, it wasn't infected, but next time it might be? Or that they can't detect an off-flavor that others would? A single anecdotal account is only that. Now, this doesn't mean I think the person is lying, I don't. It's just that it's a one-off judgment.

What I will do is take such a claim as a working hypothesis, looking for evidence it's wrong (which is all you can do in science). I'll also gather evidence that supports it, and eventually, if it looks interesting, I might do it in my own beer. That's what I did with pitching the single pack of White Labs yeast, no starter. White said he'd do that, my son has done it several times with no apparent ill-effects, and I just did it producing an excellent beer.

You reading this can take that as anecdotal, because....that's what it is.

Agree completely . We pitch at the rates we do so the yeast we want wins the race. The race against bacteria and wild yeast. The yeast then forms a protective layer of carbon dioxide, alcohol, and lowers the PH which protects itself and our beer.

we could make wort and sit it out without ever pitching yeast. It would eventually ferment and might even be good.

I kinda laugh at the hepa filter on my aeration pump and think I didn’t filter the air I was stirring with before I got a pump. Of course, we control what we can

I feel yeast viability and fermentation temperature are critical in order to duplicate results. That makes me obsessive over yeast

For this beer, it’s a new recipe I’ve never tried. I am going to make a few batches to give away over the summer. Assuming I remember how to bottle again. (Not sure what I started doing wrong there out of the blue) So I wanted to try some dry yeast. I start reading the info on it and it didn’t make sense to me

There is a lot of good info in this thread

 

[eric19312]

I think there's value that doesn't necessarily show up every time in flavors, in that it's insurance. You've probably seen me say this before, but I'll repeat it for others. My son is a microbiologist and also a home brewer. He says virtually all homebrews are "infected" in that there's dust and stuff floating in the air that ends up in our wort. Dust has bacteria on it, if we cough we expel droplets that contain bacteria, things like that.

If there's enough of those nasties in there, they can get a foothold and create off-flavors, and since bacteria reproduces far faster than yeast, it can happen fast.

A starter, by virtue of getting more yeast cells in the wort, and (in my case) taking off much faster than normal, allows the yeast the opportunity to outcompete any nasties that have fallen into the wort.

I think Dr White and your son are on the same page. Once you open that pack of yeast your yeast is contaminated. When you make a starter out of it you are propagating contaminated yeast. Starter media (low gravity wort) is excellent for propagating all sorts of bugs. If you decant and add fresh wort you are spending even more time in that low alcohol high pH ideal for expanding the contaminant populations.

Pitching more yeast into wort fights contamination by being faster to drop pH and make enough alcohol to suppress bacterial growth. But are you better off pitching 90 billion cells of yeast with very low contamination or 300 billion cells with some meaningful level of contamination?

I agree the wort you are pitching into is contaminated and a quick start should get it to a safety zone faster. And when the calculator is saying your liquid yeast pack has only 30 billion viable cells left a starter sounds like a very good idea. But that depends on the calculator being right.

 

[SteveH aka shetc]

Sanitation is not that big of a concern, the real issue is with moisture exposure. Dry yeast is extremely hygroscopic and will absorb atmospheric moisture real fast, once its water content rises above a certain threshold it will start degrading pretty quickly. I belive it would be quite difficult to avoid excessive exposure without specialized equipment.

Would a standard kitchen vacuum sealer work?

 

[Gregory T]

This is a really interesting discussion. Anyway, not sure the sticky on dry yeast is completely correct anymore

 

[CascadesBrewer]

This is a really interesting discussion.

Yes it is. Have you tried MoreBeer for inexpensive yeast?

Lots of (seemingly) smart and experienced brewers have chimed in with different info. I am making my way through Chris White's Yeast book. I am not sure I have a comprehensive yeast "strategy" but I try different things and stick with what works the best (direct pitching dried yeast, harvesting yeast slurry including S-04, direct pitching White Labs packs into 2.5 gal batches...direct pitch a WLP001 pack into a 5 gal pale ale when an unexpected slot to brew popped up).

Much of my brewing habits were formed back when dried yeast had significantly more contamination and you could not get liquid yeast with 100B to 200B cells. All the info and quality yeast available these days has changed (or at least made me question) a lot of my practices.

 

[GoeHaarden]

Nottingham is another dry yeast where people anecdotally report good results when re-pitching it. And people occasionally mentioned that they get better beer with the re-pitches.

I've re-pitched Notty with good success. I don't really see how the quality of pitchable cells in a yeast cake from dry yeast would be any different (other than strain) from that of liquid yeast.

 

[Gregory T]

Yes it is. Have you tried MoreBeer for inexpensive yeast?

Lots of (seemingly) smart and experienced brewers have chimed in with different info. I am making my way through Chris White's Yeast book. I am not sure I have a comprehensive yeast "strategy" but I try different things and stick with what works the best (direct pitching dried yeast, harvesting yeast slurry including S-04, direct pitching White Labs packs into 2.5 gal batches...direct pitch a WLP001 pack into a 5 gal pale ale when an unexpected slot to brew popped up).

Much of my brewing habits were formed back when dried yeast had significantly more contamination and you could not get liquid yeast with 100B to 200B cells. All the info and quality yeast available these days has changed (or at least made me question) a lot of my practices.

$6 a pack is Morebeer’s price. I won’t buy liquid yeast from MoreBeer. That’s another discussion

 

[Vale71]

Would a standard kitchen vacuum sealer work?

You don't really get much of a vacuum with those and then there is still the issue of exposure while handling it.

 

[schematix]

Would a standard kitchen vacuum sealer work?

My guess is yes it’ll be fine. My plan once I open my 500g pouch is to split it into 5 100G bags. I’m planning to use most of the yeast in the next 6 months.

 

[GoeHaarden]

Dry yeast is designed to be a single use product

Why? Not trying to start an argument I'm just curious if your rationale for this is science or just good advertising by the company to sell more yeast?

Take the Weihenstephan strain for instance which, to my limited knowledge, comes dry as Saflager 34/70 and liquid (WLP830 I believe). Sure we could argue that the initial cell pitch of dry 34/70 isn't reusable, but what about the cells produced throughout fermentation? I don't think dry yeast manufacturers are genetically modifying the strain to go bad after one use...

Can anyone answer this? I will continue to reuse dry yeast as I've had good results, but the whole one-and-done idea for dry yeast just doesn't make sense to me.

 

[mediant]

Can anyone answer this? I will continue to reuse dry yeast as I've had good results, but the whole one-and-done idea for dry yeast just doesn't make sense to me.

This study shows that serially repitched wet and dried yeasts perform in a similar fashion and that repitched cultures exhibit more typical fermentation and flavor profiles than fresh slurries. In addition, the study demonstrates that the accumulation of genetic and phenotypic variants is not associated with serial repitching of dried yeast cultures. Consequently, it is proposed that ADY can be reused in a similar fashion to wet yeast without any adverse effects on fermentation performance, yeast quality, or flavor production.

 

[GoeHaarden]

This study shows that serially repitched wet and dried yeasts perform in a similar fashion and that repitched cultures exhibit more typical fermentation and flavor profiles than fresh slurries. In addition, the study demonstrates that the accumulation of genetic and phenotypic variants is not associated with serial repitching of dried yeast cultures. Consequently, it is proposed that ADY can be reused in a similar fashion to wet yeast without any adverse effects on fermentation performance, yeast quality, or flavor production.

Thanks. This is what I'm after. Do you by chance have the whole study?

 

[mediant]

Thanks. This is what I'm after. Do you by chance have the whole study?

PM sent.

 

[Denny]

Is it not true that for certain styles under-pitching brings out desirable flavors by intentionally stressing yeast?

No, it's not true. Actually, the opposite. This is the explanation from Dr. Clayton Cone of Lallemand....you can read more in my BYO column..."
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."

 

[mediant]

No, it's not true. Actually, the opposite. This is the explanation from Dr. Clayton Cone of Lallemand....you can read more in my BYO column..."

And yet it is Lallemand that recommends to uderpitch their Munich yeast to increase the banana flavor:
"Pitching rate for primary fermentation
The recommended pitching rate is 100g/hl to achieve up to 5 million live cells per ml.
A lower pitching rate of 50g/hl can be used to increase ester concentration notably isoamyl acetate
which is responsible for banana flavors. See below for more details."

 

[hopjuice_71]

This study shows that serially repitched wet and dried yeasts perform in a similar fashion and that repitched cultures exhibit more typical fermentation and flavor profiles than fresh slurries. In addition, the study demonstrates that the accumulation of genetic and phenotypic variants is not associated with serial repitching of dried yeast cultures. Consequently, it is proposed that ADY can be reused in a similar fashion to wet yeast without any adverse effects on fermentation performance, yeast quality, or flavor production.

mediant beat me to it. I went down a rabbit hole of reading the primary literature regarding activated dry yeast (ADY) performance. I found this paper as well. One might criticize this study because it was performed by Lallemand; however, several other studies performed by academic researchers back up many aspects of this (though focus only on gen 0).

By way of summary, significant performance differences have only been associated with lager strains, and the nature of the performance differences is inconsistent between reports. Importantly, genetic stability, and indeed INCREASED genetic stability relative to liquid cultured counterparts, has been repeatedly associated with ADY, meaning it is no more prone, and possibly even less prone, to generating undesirable petite mutations.

Initially, viability is an issue with ADY (anywhere from 50-80% viability); however, this is clearly not an issue with subsequent generations. Regarding the initial dry pitch, if viability is accounted for in pitch rates, the abundance of dead cells is no more than what would be added in a dose of yeast nutrient.

At the end of the day, having read all these studies, I personally have no reservations using a starter for ADY or repitching.

 

[mongoose33]

So....we have two different.....views, opinions, evidence....from both @Denny and @mediant . I've been working a lot trying to understand yeast--maybe a fool's errand on my part --so I turned to my "Yeast" book co-authored by Chris White and Jamil Zainasheff.

• On page 121 there is this quote: "In general, underpitching affects flavor more, while overpitching negatively affects yeast health over more generations."
• Then on page 104 is this, in relation to pitching rates: "More cell growth usually results in more flavor compounds." There's more cell growth with an underpitch, I believe.
• But then again, in the table on page 105, it shows that with an increased pitching rate, esters drop.

The above, while seemingly contradictory, is why I've struggled in trying to understand yeast. Yet, esters aren't flavor compounds, they're aroma compounds, so maybe all this isn't as contradictory as it appears (at least to me).

Regardless, there does appear to be contradictory findings regarding all these things. Just look at the posts by Denny and Mediate. I think what we're all trying to do here is figure this out, and all this contradictory stuff isn't helping. I'm sure they're both on the same mission, i.e., figure it out.

Perhaps it matters more with lagers than ales. Perhaps it matters more with some strains than others. Perhaps it's related to fermentation temp. Perhaps....who the heck knows?

 

[Big Monk]

So....we have two different.....views, opinions, evidence....from both @Denny and @mediant . I've been working a lot trying to understand yeast--maybe a fool's errand on my part --so I turned to my "Yeast" book co-authored by Chris White and Jamil Zainasheff.

• On page 121 there is this quote: "In general, underpitching affects flavor more, while overpitching negatively affects yeast health over more generations."
• Then on page 104 is this, in relation to pitching rates: "More cell growth usually results in more flavor compounds." There's more cell growth with an underpitch, I believe.
• But then again, in the table on page 105, it shows that with an increased pitching rate, esters drop.

The above, while seemingly contradictory, is why I've struggled in trying to understand yeast. Yet, esters aren't flavor compounds, they're aroma compounds, so maybe all this isn't as contradictory as it appears (at least to me).

Regardless, there does appear to be contradictory findings regarding all these things. Just look at the posts by Denny and Mediate. I think what we're all trying to do here is figure this out, and all this contradictory stuff isn't helping. I'm sure they're both on the same mission, i.e., figure it out.

Perhaps it matters more with lagers than ales. Perhaps it matters more with some strains than others. Perhaps it's related to fermentation temp. Perhaps....who the heck knows?

The best source of information on fermentation parameters and how they affect esters and higher alcohols that I’ve ever read was Greg Casey’s 2005 presentation to Rocky Mountain Microbrewers Symposium.


This is the source material for most of Yeast chapter in BLAM.

 

[Gregory T]

No, it's not true. Actually, the opposite. This is the explanation from Dr. Clayton Cone of Lallemand....you can read more in my BYO column..."
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."

Brew Like A Monk. Recommends underpitching. I happen to disagree with this recommendation, but it is there

 

[Gregory T]

Interestingly enough while BLAM recommends underpitching, my understanding is the monks themselves typically pitch at unheard of rates in the U.S.

Around 5.0 million cells/ml/degree Plato

And under aerating the wort

 

[Big Monk]

Brew Like A Monk. Recommends underpitching. I happen to disagree with this recommendation, but it is there

You have to put that in context: if the Trappists underpitch, it’s simply because they have SUPER healthy and active yeast available that acclimated precisely to their brewery.

Should the average brewer under pitch? Nope. Should the more advanced brewer with healthy and active yeast underpitch? For sure is that nets the desired results.

My opinions are different than most but then again I brew only Trappist type ales. I do tons of things that go against the grain for fermentation and pitching because they give me the results I desire.

 

[Big Monk]

Interestingly enough while BLAM recommends underpitching, my understanding is the monks themselves typically pitch at unheard of rates in the U.S.

Around 5.0 million cells/ml/degree Plato

And under aerating the wort

That’s not true. At least for pitching during primary fermentation.

You may be confusing bottling rates with pitching rates. Nearly all of the Trappists and others like Duvel, pitch at < 0.75 M/ml/°P.

My MO is as follows:

1.) Pitch around 1.25-1.40 M/ml/°P
2.) < 8 ppm O2
3.) Limit Zinc to minimum (0.3 ppm)
4.) No temperature control

 

[Gregory T]

That’s not true. At least for pitching during primary fermentation.

You may be confusing bottling rates with pitching rates. Nearly all of the Trappists and others like Duvel, pitch at < 0.75 M/ml/°P.

Let me see if I can find the source. Interestingly it goes with what Denny said about low aeration causing high ester

 

[Gregory T]

You have to put that in context: if the Trappists underpitch, it’s simply because they have SUPER healthy and active yeast available that acclimated precisely to their brewery.

Should the average brewer under pitch? Nope. Should the more advanced brewer with healthy and active yeast underpitch? For sure is that nets the desired results.

My opinions are different than most but then again I brew only Trappist type ales. I do tons of things that go against the grain for fermentation and pitching because they give me the results I desire.

Me too. Well I have ventured into saisons recently

 

[Gregory T]

That’s not true. At least for pitching during primary fermentation.

You may be confusing bottling rates with pitching rates. Nearly all of the Trappists and others like Duvel, pitch at < 0.75 M/ml/°P.

My MO is as follows:

1.) Pitch around 1.25-1.40 M/ml/°P
2.) < 8 ppm O2
3.) Limit Zinc to minimum (0.3 ppm)
4.) No temperature control

Haven’t found the original source material on it yet but here is a thread about low oxygen in wort

https://www.homebrewtalk.com/forum/threads/belgian-experiment-oxygen-and-pitch-rates.594386/