[yso191]

I didn't want to hijack Jim's thread on oxygenating wort so I thought I'd start a new thread specifically on when it is good to purposely stress yeast.  I have been oxygenating my wort every time; 1 liter for normal gravity beers and 2 liters for big beers. 

In the thread started by Jim, people have mentioned that for certain beers they don't oxygenate because they are looking for increased ester production.  I am looking for a new tool for my brewing practice, so what beers are best without oxygen added, and are there other ways of stressing yeast (under-pitching?) that are useful in specific circumstances?  If so, what styles and how do you stress the yeast successfully?

[pinnah]

I have thought about this a bit lately.

I have been trying to nail down a "session" ipa, and have been getting too thin, dry and seemingly over attenuated attempts.

This last batch, I purposely used a 4 month old smack pack without a starter and pitched it right into 1.054 wort.

I don't have my notes with me, but IIRC, I only got about 68% attenuation.   I am liking the results so far.

[Stevie]

I underpitch saison by 25-30% the recommended dose to get more of the flavors I like. I then hold the temp at 68° until there is a good amount of krausen.

[hopfenundmalz]

Chris White was at our LHBS for big brew. Asked about English ales and esters, he said the English brewers underpitch.

I used to make some tasty English bitter and milds back in the day before I learned better techniques. Then I learned how to make lagers. I was pitching big and oxygenating. Those lacked character. Stopped using O2 and it was better. Will try about 2/3 the pitch rate next time, maybe one half.

One of the local brewpubs doubles the pitch rate of the house yeast, WLP 022 Essex Ale, when they want to make a clean APA.

[morticaixavier]

I have thought about this a bit lately.

I have been trying to nail down a "session" ipa, and have been getting too thin, dry and seemingly over attenuated attempts.

This last batch, I purposely used a 4 month old smack pack without a starter and pitched it right into 1.054 wort.

I don't have my notes with me, but IIRC, I only got about 68% attenuation.   I am liking the results so far.

if what you are after is less attentuation is seems like mash temp and malt choices would be safer than counting on the yeast pooping out too soon. what happens if you bottle and a few cells wake up and decide there is more food there then they thought?

my session method is to mash very very high (162) for 45 minutes and include a healthy portion of crystal malt.

[HoosierBrew]

I underpitch saison by 25-30% the recommended dose to get more of the flavors I like. I then hold the temp at 68° until there is a good amount of krausen.

+1. I underpitch on Saison too. A healthy strain is plenty voracious enough to tear through a typical non -imperial strength wort, and gives better esters underpitched too, IMO.

[klickitat jim]

I think there are several ways to play with the flavor profile. I'd pick the method that best fits my overall goal. For example, if I would like more esters but also planned on harvesting and repitching, then I would adjust my pitching rate and fermentation temp to increase esters but still oxygenate so I end up with relatively healthy yeast. If I didn't plan to repitch I might oxygenate less or skip it and aerate instead. If I wanted reduced attenuation I agree with Jonathan and would up my mash temp, change grist, or go with a less attenuative yeast.

Most parts of brewing are like playing a musical chord. Major is 1 3 and 5, minor is a flat 3rd, etc...it all works together

[erockrph]

I think there are several ways to play with the flavor profile. I'd pick the method that best fits my overall goal. For example, if I would like more esters but also planned on harvesting and repitching, then I would adjust my pitching rate and fermentation temp to increase esters but still oxygenate so I end up with relatively healthy yeast. If I didn't plan to repitch I might oxygenate less or skip it and aerate instead. If I wanted reduced attenuation I agree with Jonathan and would up my mash temp, change grist, or go with a less attenuative yeast.

Bingo. First off, I wouldn't necessarily think of it as "purposefully stressing yeast" - to me that sounds like you are going so far to the extreme that the yeast is going to do all kinds of horrible things. But there are certainly several ways to adjust the initial conditions of the wort/yeast to get the results you're looking for. I wouldn't necessarily go out of my way to stress the yeast, but using lower pitching/nutrient/oxygenation rates are certainly all valid options available to the homebrewer. I do I think I'd choose to manipulate other factors first (mash temp & fermentation temp primarily).

I think homebrewing has come along so far because of the quality of the yeast that has become available, and because most good homebrewers place good fermentation practice as their top priority (and rightfully so). But I think that this has also led to some brewers falling under the impression that you absolutely have to pitch as much yeast as Mr Malty tells you to in all cases. I don't see that as the case. I think if you are managing all your other factors properly (aeration and temp control), then you can pitch at a lower rate in some styles and have excellent results. I'm not saying that 1 vial of yeast could work for 10 gallons of barleywine, but I like to pitch about 1/2-2/3 of what Mr Malty recommends when I'm brewing a hefe to get the flavor profile I'm looking for.

[HoosierBrew]

I think there are several ways to play with the flavor profile. I'd pick the method that best fits my overall goal. For example, if I would like more esters but also planned on harvesting and repitching, then I would adjust my pitching rate and fermentation temp to increase esters but still oxygenate so I end up with relatively healthy yeast. If I didn't plan to repitch I might oxygenate less or skip it and aerate instead. If I wanted reduced attenuation I agree with Jonathan and would up my mash temp, change grist, or go with a less attenuative yeast.

Bingo. First off, I wouldn't necessarily think of it as "purposefully stressing yeast" - to me that sounds like you are going so far to the extreme that the yeast is going to do all kinds of horrible things. But there are certainly several ways to adjust the initial conditions of the wort/yeast to get the results you're looking for. I wouldn't necessarily go out of my way to stress the yeast, but using lower pitching/nutrient/oxygenation rates are certainly all valid options available to the homebrewer. I do I think I'd choose to manipulate other factors first (mash temp & fermentation temp primarily).

I think homebrewing has come along so far because of the quality of the yeast that has become available, and because most good homebrewers place good fermentation practice as their top priority (and rightfully so). But I think that this has also led to some brewers falling under the impression that you absolutely have to pitch as much yeast as Mr Malty tells you to in all cases. I don't see that as the case. I think if you are managing all your other factors properly (aeration and temp control), then you can pitch at a lower rate in some styles and have excellent results. I'm not saying that 1 vial of yeast could work for 10 gallons of barleywine, but I like to pitch about 1/2-2/3 of what Mr Malty recommends when I'm brewing a hefe to get the flavor profile I'm looking for.

+1.

[mabrungard]

Chris White was at our LHBS for big brew. Asked about English ales and esters, he said the English brewers underpitch.

I used to make some tasty English bitter and milds back in the day before I learned better techniques. Then I learned how to make lagers. I was pitching big and oxygenating. Those lacked character. Stopped using O2 and it was better. Will try about 2/3 the pitch rate next time, maybe one half.

One of the local brewpubs doubles the pitch rate of the house yeast, WLP 022 Essex Ale, when they want to make a clean APA.

There is merit to what constitutes a 'proper' pitching rate. I've been working with Chris White on this calcium/yeast issue and I asked specifically if he knew of a reason why lager brewing typically employs roughly twice the cell count. I suggested that it was only the result of empirical results...lagers pitched with high cell counts tasted better. The same guidance is valid for any brewing. If the resulting beer tastes better with either higher or lower cell counts, oxygenation or not, then that is the right way to go. I didn't get the impression that there is a hard and fast rule in this area.

[pinnah]

I have thought about this a bit lately.

I have been trying to nail down a "session" ipa, and have been getting too thin, dry and seemingly over attenuated attempts.

This last batch, I purposely used a 4 month old smack pack without a starter and pitched it right into 1.054 wort.

I don't have my notes with me, but IIRC, I only got about 68% attenuation.   I am liking the results so far.

if what you are after is less attentuation is seems like mash temp and malt choices would be safer than counting on the yeast pooping out too soon. what happens if you bottle and a few cells wake up and decide there is more food there then they thought?

my session method is to mash very very high (162) for 45 minutes and include a healthy portion of crystal malt.

Perhaps I am confusing myself here.  I guess I was thinking that by not pitching an active starter and by only pitching an old smack pack I would be somehow limiting my attenuation?

I checked my notes last night and that beer went from 1.054 to 1.015.
I mashed @158 and had about 8% crystal.

[morticaixavier]

you may limit attenuation by underpitching or not giving enough o2 for proper reproduction but it's because the yeast stall. there is still fermentable sugars there and they may ferment at some point in the future when one little yeast cell finds some sterols from a dead neighbor and starts reproducing again.

[dmtaylor]

Belgian beers are the classic example of where it is appropriate to underpitch.  Hefeweizen might be another example since it shares a lot of similar attributes to Belgians.

[denny]

Belgian beers are the classic example of where it is appropriate to underpitch.

Maybe some of them, but by no means all.

To my way of thinking, trying to control beer character through pitching rate is so inexact as to be close to folly.  How do you know how much to "underpitch"?  Do you count the cells to make sure you're underpitching but not by too much?  How does the viability of the yeast figure in?  Not to mention that there are experts who feel like pitching less yeast actually reduces esters.  It's far better to control esters through yeast strain choice, recipe design, and fermentation temperature.

[erockrph]

Belgian beers are the classic example of where it is appropriate to underpitch.

Maybe some of them, but by no means all.

To my way of thinking, trying to control beer character through pitching rate is so inexact as to be close to folly.  How do you know how much to "underpitch"?  Do you count the cells to make sure you're underpitching but not by too much?  How does the viability of the yeast figure in?  Not to mention that there are experts who feel like pitching less yeast actually reduces esters.  It's far better to control esters through yeast strain choice, recipe design, and fermentation temperature.

I would counter that all your questions can be applied equally as well to pitching "the right amount". I do agree that I would chose other options before I start playing with pitching rate, but it is certainly another factor that you can control as a brewer.

I think of pitching rate similar to how I think of IBU's - the calculators out there aren't going to give you exact predictions that can be verified by a lab. But if you are consistent in how you use them, then they can give you a good enough ballpark to be able to make adjustments within a given recipe on your own system.