Practical yeast starting and pitching

I pretty much agree. I think that a discussion about what the factors are and how to balance them would be better served.

For instance from the Maltose Falcon's link:
Ale strains usually need between 8-12 part per million (ppm) while lager strains require slightly higher amounts (10-15 ppm).

I have an issue with the statement. Palmer says that we pitch a large cell count when making a lager is to suppress yeast activity.

I posted this before:


http://brewiki.org/BeerFlavours#Esters

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.

So it seems to me that it's only the large pitch of yeast which requires more oxygen. From what I've read it's that amount of O2 relates to the cell count of the pitch. So it's not that the yeast require that amount of O2, it's more that the stated amount is the parameters for the beer that we want to make. Less esters = more cells, more cells = more O2.

~~~

Another thing it's not aeration vs oxygenation. It's how many ppm that you need and how to get it. Standard methods only provide ~8ppm saturation when using ambient air. To get about that it's common to use pure O2. But I imagine that you could also keep pumping sterile ambient air into the head-space. This in part would mimic an open fermentor.

~~~

Anyway, I'm sure that my cliff notes aren't that accurate. And I'd like some input, I'm just trying to illustrate some of the factors.

 

Interesting snippet... Acetyl CoA is essential for fatty acid production by Fatty Acid Synthetase and for specific esterification reactions (Esters = Alcohol + Acid + loss of water), so the direct correlations between ester production, biomass production and Acetyl-CoA metabolism seem logical.

One interesting, kinda fun fact, is that Acetyl-CoA and its derivatives (proponyl, malonyl, methyl-malonyl-CoA, etc.) are all cell membrane permeable, so if inclined, you could dose your wort with Acetyl-CoA at the appropriate time and potentially kick up ester production.

I wish I knew more about how oxygenation feeds into metabolism (other than the obvious TCA cycle, etc. etc.); might pull some papers when I get home for some fun reading...

 

He's using a rehydrated dry yeast in this test. Generally speaking from my understanding oxygenation is not required for dry yeasts as (IIRC) they have glycol reserves that liquid yeast does not have that will help with the reproduction phase.

 

Another useful calculator for making starters...
http://www.yeastcalc.com/

 

Yeah, that is what I thought. More of a demonstration than a rigorous experiment.

 

I would take MB Raines advice on yeast over John Palmer. No disrespect to John on this, but MB Raines has a PhD in microbiology and does yeast research for a living.

Somewhere I remember that lager yeast strains benefit from more oxygen vs ale yeasts. You want more cells and more O2 for lagers.

 

Raines never commented on why there is a large pitch rate for Lagers. I used Palmer's quote to illustrate one of the subjects that I wanted to discuss, how the pitch rate and yeast growth affects esters. Palmers quote was a lead into the link that I posted, so there no disagreement.

Does the lager cell actually require more O2 or is it how it is being used - in a manner to suppress errors? Maybe it just semantics.

But I do question his assertion (in the link posted) that you can make starters at 75*F. Dan Gordon states the he found that starters at the temp created mutant cells. Maybe the caveat is the Dan is talking Lager yeast.

 

Now I see your point.

One of the homebrew myths is that you get esters from underpitching. I have seen the Dr. Clayton Cone quote some time back.

 

Yeah, I'm just kinda talking out of my butt, but I do find this interesting.

FWIW I made a beer using wyeast 3725, which arrived with all of the ice packs gone and it was fairly warm. I was in a hurry to brew and while I did make a starter, I should of stepped it up once more. So I did under pitch.

The beer turned out nice, but seems sweet. I shared it with another HB'er and he seemed to agree that the beer was too fruity. Looking at my notes it probably didn't totally finish out either, so I have two errors.

If I can I'm going to try and make the same beer with a bigger starter (I have another package). I'm eager to see if the final beer changes much. I might also do the fast fermentation test.

 

I double the amount of O2 for my lagers (vs. ales for same gravity) and I like the results.

 

Jeff,

I found it interesting that you stated: “One of the homebrew myths is that you get esters from underpitching.”

In the article written by Jamil Zainasheff entitled “The Secret to Healthy Yeast – Making a Starter” (Zymurgy March/April 2007) there is the below quote:

“There is also an upper limit to how much yeast you should add. Logsdon says, “I try to stay within 20 percent of my ideal pitch rate and I prefer to slightly under pitch rather than over pitch. This causes more cell growth, more esters and better yeast health. Over pitching causes other problems with beer flavor, such as a lack of esters. Changes in the flavor profile are noticeable when the pitch rates are as little as 20 percent over the recommended amount.”

My read of the above (“I prefer to slightly under pitch rather than over pitch. This causes more cell growth, more esters …”) is that underpitching will indeed increase the production of esters. I take it that you disagree with Dave Logsdon?

Cheers!

 

I have looked at Yeast and they only say only a little about this, and it is opposite to what Dr. Cone says.

Neva Parker of White Labs said at her NHC talk that you don't get more esters when you under pitch, but you do get more fusels. She was questioned on that from the audience, and then refered to Japanese research papers to back that up. Wonder what they talk about when this comes up around the office?

If the yeast is stressed or underaerated you get more esters when you pitch. This may all be an "it depends" question.

I will say that the Bitters I make have lost a little when hit the right pitch rate and used O2 for aeration. Might have to experiment and split a batch. Over pitch some, under pitch some, just shake some in the carboy.

Dave Logsdon is a brewer now.

 

FWIW, MB Raines seems to think that underpitching will produce increased esters:

“If underpitched the yeast will spend much more time trying to grow to adequate quantities. During this extended growth period the yeast tend to secrete more esters and fusel alcohols. Moreover they may not have a sufficient number to adequately metabolize (digest) all of the fermentable sugars. So what you end up with is a beer with off-flavors (such as esters, fusel alcohols, diacetyl, acetaldehyde) and a high finishing gravity.”

The above is from: http://www.maltosefalcons.com/tech/yeast-propagation-and-maintenance-principles-and-practices

Cheers!

 

<more esters when you under pitch, but you do get more fusels

Aren't fusels esterfied?

 

No.... then they wouldn't be alcohols (They'd be named differently if using IUPAC nomenclature, and also in common naming). Fusel alcohol = propanol, butanol, amyl alcohol, etc. plus isomers where appropriate.

EDIT. Forgot to mention, generic/catch all description of fusel alcohols is alcohols with greater than 2 carbons.

 

To add on to barfdiggs explaination, esters have a carbonyl functional group. The "R" is some type of hydrocarbon.
Alcohols have an alcohol functional group, just an oxygen (and hydrogen) on a hydrocarbon.
Where a functional group is a type of atom-bond characteristic of that class of molecule.

Do I hear phenols?

 

I don't know, do you? Let us know if barfdiggs' avatar starts telling you what to do.

 

Corgi's possess powers of mind control through epic cuteness.