Yeast Stress. Effects and Myths

[Pikey]

............To Pikey: You asked if I believe in stress causing off-flavors. I think I've read myself into saying "Yes" to that question.

The beer forum I'm on talks about sways of single digits of degrees having detrimental affects! Some are rabidly loyal to this belief.

Well you know what specialist forums are like - There are always those who insist "My way is the only way" and shout down any discussion.

It's easy enough for you to check for yourself mate - choose a yeast which they all say is susceptible to "off flavours" (Bread yeast )

do a wash at 7% like what you are told - then do another alongside and take it as high as you can 13-14 % ?

Still 'em both and come back and tell us what "Off-flavours" taste like !

I can't do it myself, cos I use 5 kg sugar, plus whatever is in the ingredients in 25 litre washes and I never have an issue, so I'm not going to be doing any "Half strength" ferments !

[johnsparrow]

I agree with all of the advise saying 'try it out for yourself', there can be so much contradiction on the internets that instead of being able to learn which is the best way to go about doing something all you find is that you end up with a mass of confusion and more questions about something that started off as a simple yes/no question.

[butterpants]

TOTALLY and UTTERLY strain dependant. It depends is the answer for everything here

[zapata]

Just to be clear, I have done that. Sugar washes fermented with 1118 at various levels, most everything else being the same. Meaning not perfectly controlling and documenting every detail, but just repeating them in whatever conditions and practices were typical for me at the time.

I'm not going to hunt around to look for exact specifics, but I occasionally make myself "shit I've learned" notes. I have one in the beginning of my last notebook that says "neutral: not sure I can tell a difference between 10% and 12%, can between 10% and 17%. Limit to 10%? 12%? look at batch size logistics to decide."
Then a later note adds on
"12% doesn't offer any advantage over 10"

Now, the "batch size logistics" means that for the fermenter/s and still/s and time I had at the time, for some procedural reason 12% offered no benefit. Just means that I got all the etoh I wanted or could use from 10%. That'd be particular to me and wouldn't necessarily apply to others. But I would expect others to be able to see the differences between 10 and 17%, either in flavors, or size of cuts, or not if they have some typical condition or practice that matters.

Was it actually "stress" causing "off flavors"? I don't really care for myself, I'll just trust myself that I don't want to do 17% washes for neutrals. But for the conversation, maybe it isn't yeast stress at all. A 17% fermentation is going to take longer to ferment, does that just give other microbes more of a chance to add their own flavors? Does the higher alcohol level shift the equilibrium of purely chemical changes in a less than desirable way e.g. will quantitatively more ethyl esters form in a 17% abv wash sitting for 2-3 weeks than in a 10% wash in 1 week? Is it a matter of relative volatility of congeners being less desirable at 17% than 10. Could be. Could be anything really though, in fact could be something counter to general advice like a 17% abv wash actually needs MORE nutrients and will then be just as neutral, or better aereation/temp control/ph etc.

The scientist in me is interested in those questions and answers. The practical stiller, much less so. I've got experience telling me 10% is better, and I've little to no motivation to make 17% work as well. 17 would just give me more etoh in the low wines, but I'd still do a large stripping run to net me a keg full of low wines, which in my 2" column already takes forever and produces a year's worth of booze. I don't have any use for the extra 7%.

[shadylane]

I don't like to stress yeast.
Yeast is working hard to supply me with alcohol, it just don't seem right, to be mean to yeast.
My fermenting protocol, is to give the yeast enough fermentable sugar to make 6% - 10% alcohol
The 6% limit is based on efficentcy, less than that and I'd be wasting energy, and not getting any advantage
Higher than 10% alcohol and the yeast is getting weaker.
It's survival limits of temp and neutrients get MUCH narrower.
Maybe I could be mean to the Yeast and stress it for a specific flavor profile.
But it wouldn't be repeatable

[Oldvine Zin]

+ 1 shady

OVZ

[vqstatesman]

Interesting thread gents. I was always of the impression high sugar content and too much nutrients could cause off flavours too. I have just recently began to question this.

Pretty sure we all agree that temperature plays a big part in flavour profile. Push any yeast beyond above its maximum range and it will produce off flavours.

For any of the rum maker you should check out the following link. The recipe comes from someone with good knowledge of the distilling industry. As you will see he uses one tsp DAP per gallon of wash.
http://www.artisan-distiller.net/phpBB3 ... 6417aa106c" onclick="window.open(this.href);return false;" rel="nofollow

[fizzix]

............To Pikey: You asked if I believe in stress causing off-flavors. I think I've read myself into saying "Yes" to that question.

The beer forum I'm on talks about sways of single digits of degrees having detrimental affects! Some are rabidly loyal to this belief.

Well you know what specialist forums are like - There are always those who insist "My way is the only way" and shout down any discussion.

It's easy enough for you to check for yourself mate - choose a yeast which they all say is susceptible to "off flavours" (Bread yeast )

do a wash at 7% like what you are told - then do another alongside and take it as high as you can 13-14 % ?

Still 'em both and come back and tell us what "Off-flavours" taste like !

I can't do it myself, cos I use 5 kg sugar, plus whatever is in the ingredients in 25 litre washes and I never have an issue, so I'm not going to be doing any "Half strength" ferments !

I've conceded! I've conceded! Let go of my arm! I am glad you questioned me in the other thread.

[durty_dunderpants]

good read bout lost spirits salty staves. i've been looking for more info 'bout rumours of bananas in muckpits given the lack of ideal bacteria sources available to me. buuut.. are we seriously meant to be drinking that rum at 68% without diluting it?!

fizzix i really think the best advice to give is rarely "yes it's always an issue" or "it's rubbish never happened to me" because absolutes are seldom true with this kinda thing. drawing attention to something someone may not have considered though is generous and good advice . as a few people have said, it really depends on what the intended product as to whether it's desired; and that the effects can vary depending on temperature sugar and nutrients etc. and on!
some yeasts will have a much wider range than others before the effects are noticeable even, which i'd guess is where a lot of the differing opinions come from. some yeasts have really individual traits that need special handling to avoid stress while others don't seem to be bothered how mean you are to them!

[Max_Vino]

This might help. I ran some tests on yeast stress a few years back.

viewtopic.php?f=40&t=43252

These days I control all the variables I can to produce a stress free wash including yeast selection. I even play classical music for them.

Cheers,
Max

[Oldvine Zin]

These days I control all the variables I can to produce a stress free wash including yeast selection. I even play classical music for them.

Cheers,
Max

Pink Floyd for HBB, Reggae for all my rum ferments, and good ol banjo works for whiskeys.

OVZ