Author: Marshall Schott
“Pitch cool, always! This will limit unwanted ester production. I always chill my wort to 2˚ below my intended fermentation temp.”
This is a quote from my Homebrewing Heuristics post, the same advice I’ve given countless times in many other places. It makes perfect sense, and as with many things that do, I accepted it without anything less than anecdotal evidence to back it up. I’m not sure when or really even why I started making this recommendation, it just seems so right. And I’m not the only one doing it.
At the 2011 National Homebrewers Conference, Jamil Zainasheff, co-author of Yeast: The Practical Guide to Beer Fermentation and Chief Heretic at Heretic Brewing Company, gave a presentation on Growing, Harvesting, and Pitching Yeast. On the last bullet-point of the second-to-last PowerPoint slide, under the section labelled “Pitching Yeast,” Jamil writes:
Start slightly low, raise several degrees F for the last 1/3 – 1/4 of fermentation
I interpret this as meaning, pitch yeast into wort that is slightly cooler than target fermentation temp, which is fully inline with the recommendation he often makes on BrewStrong and in his Style Profile articles in BYO. As I was making a starter a couple weeks ago, I happened to glance at the instructions on the vial I’d just emptied and was reminded that White Labs recommends pitching into wort that is 70-75°F. I’d read this before and had assumed the reason yeast manufacturers make this recommendation is that the warmer environment encourages quicker growth, thereby decreasing the risk of infection and poor attenuation. Then I recalled that Chris White, president of White Labs, was the other author of the Yeast book. Huh. My curiosity piqued by this incongruous realization, I figured it’d be best to seek clarification from the source and shot an email to White Labs. The first person who responded initially just reiterated what the vial says then later admitted, “Honestly I have not heard that!” I briefly explained the reason behind why many of us pitch cool, alluding to Narziss’ method for lager beer, and mentioned many homebrewers have adopted a similar method for ale. About a week later, I received a response from another White Labs staff who clarified,
It does reduce esters, but if you pitch the yeast warm and then drop the temp down when it gets going, there will be very minimal ester production versus if it was pitched cold, which can take a very long time for the fermentation to get going.
Cool, White Labs acknowledges there may be some benefit to pitching cool, at least for those brewers seeking to keep esters to a minimum. But how big of a difference does it really make? I decided it was time to put my money where my mouth is and test this theory that I’d accepted as doctrine and preached as truth!
| PURPOSE |
To investigate the qualitative differences wort temperature at time of yeast pitch has on 2 beers produced from the same wort and fermented with the same yeast.
| METHOD |
I already had plans to make a batch of Tiny Bottom Pale Ale for my Seeking The Source xBmt, so all I did was bump up the batch size a couple gallons for this one. I batch sparged, collected my wort, and brought it up to a boil.
I’d recently purchase a few ounces of East Kent Goldings and thought this might be a good batch to try them out in since the normal hop I use is also of English origin.
Once the boil was complete, I used my JaDeD King Cobra IC to chill the wort to 74°F, which was 6°F warmer than the temperature of my groundwater, exactly 10°F warmer than my preferred pitch temp for ale. About 2.5 gallons of wort was racked into two 3 gallon Better Bottles, one being placed in my ferm chamber to continue chilling while the other was left to sit outside of the chamber to stay warm. Coincidentally, it was exactly 74°F in my garage that day.
I came back 4 hours later to discover the cool pitch wort had dropped those last few degrees, so I placed the warm pitch carboy next to it in the chamber, it was 10°F warmer than the cool pitch.
Equal-sized starters of WLP090 San Diego Super Yeast were pitched into both carboys.
I completely expected the warm pitch beer to show active signs of fermentation first, but at 12 hours, both looked fairly similar. I guess the warm pitch carboy did have what appeared to be a slightly more developed krausen.
At 24 hours, the beers looked even more similar and the batch pitched warm had finally dropped to the same temp as the batch pitched cool, both were kicking ass.
After 6 days and a slight ramp in temp to ensure complete attenuation, the krausen on both beers fell and fermentation activity appeared to have slowed.
I took an initial FG sample, let the beer sit at 72°F for 3 more days, then took another FG sample, it was the same as the first.
I noted both as finishing at 1.011, the tiny bit of foam on the warm pitch sample made it look slightly lower. Since FG was stable and I detected no off-flavors, it was time to keg.
The beers were placed on gas in my keezer for just under a week before being evaluated, both had cleared considerably in this time.
| RESULTS |
A total of 13 people participated in the tasting panel and, as always, they were completely blind to the nature of the xBmt. Participants were asked to complete a triangle test, knowing only that of the 3 beers presented, 2 were the same and 1 was different. In this case, the tasters received 2 warm pitch beers and 1 cool pitch beer. Those participants who accurately selected the beer that was different were then asked to complete a more detailed survey comparing just the 2 different beers, still not knowing what was different between them.
To conclude that pitching temp had a significant impact on the beers, 8 of the 13 people would have had to select the the cool pitch beer as being different (p<0.05). In this case, only 4 tasters were accurate in their selections, 8 more selected either of the other warm pitch samples, and only 1 reported experiencing the beers as having no discernible difference.
My Impressions: When I was presented with both beers, even knowing the variable being tested, there was absolutely no way I could tell them apart. On numerous occasions, I’d pour myself a few samples, close my eyes, jumble the placement, walk away, return, jumble again while singing Gloria Estefan tunes to distract my mind, then sample and try to pick the different one. I couldn’t do it. Not once. They looked, smelled, tasted, and mouthfeel’d (?) like they’d been poured from the same exact faucet. Any differences fell below my threshold of perceptibility.
| DISCUSSION |
I really didn’t expect these results. At all. “Pitch cool, always!” My modus-operandi. Go search any of the plethora of homebrewing forums I participate in and you’ll undoubtedly come across numerous recommendations to others that pitching yeast into wort that’s 1-2°F cooler than their target fermentation temperature will produce a better beer. Can it really be that this recommendation is bullshit? To be honest, I was fully prepared to pen a solid I-told-you-so article, and now I’m left with more questions than answers: Does pitching cool just matter for lagers? Does it even matter for lagers? What about high OG beers? Maybe this is another pro vs. homebrew scale issue? Is 10°F not a big enough difference? Are these results a fluke? I truly am surprised by how similar the 2 beers were. A part of me is pleased to know the recommendation printed on commercial yeast packages isn’t bad, as I’d previously believed, while another part of me is struggling with the reality that…
I was wrong.
I don’t mean to be dramatic here, or make light of situations experienced as significant by others, but admitting this to myself has brought up feelings similar to those I felt when abandoning other beliefs I clung to so dogmatically. Not being one to base my decisions to change on a single thread of evidence, I have since pitched yeast into warm ale wort, 74°F in all cases, on 3 more occasions. Each beer fermented fine, fully attenuated, and tastes just as I expected. Man, oh, man. To be sure, the advice to pitch cool isn’t necessarily bad, it doesn’t make your beer any worse, it doesn’t hurt a damn thing, it just appears in some situations to be empty advice, a distinction without a difference. Furthermore, I’m not terribly comfortable accepting that pitching warm is fine in all scenarios… yet. Until there’s some solid evidence to support whether it does or doesn’t matter, it behooves me to suggest brewers making cool fermented lager and hybrid beers continue pitching cool, if that’s what’s worked. Another situation where I think it remains beneficial to pitch cool is for those brewers who don’t have precise control over their fermentation temp, as pitching warm without the ability to chill the beer relatively quickly will almost certainly result in a beer actively fermented outside of the appropriate temp range. Lager and high OG pitch temp exBEERiments have been added to the list, I’m anxious to analyze those results. Who knows, maybe I’m wrong about that as well. Only time, and more experimentation, will tell.
A final note: it’s results like this that remind me how important this type of experimentation can be! Most brewers, regardless of process, can split wort into a couple different fermentors for split-batch comparisons. I’d really like to see more people doing stuff like this and sharing their results on personal blogs or in forums like ExperimentalBrew.com. This is how we grow.
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33 thoughts on “exBEERiment | Yeast Pitch Temperature: Cool vs. Warm In An American Pale Ale”
Tremendous news for those who struggle to cool to fermentation temperture, let alone below it. Could be a real time saver.
A great experiment however, it begs the questions: are the results you found indicative of the type of yeast you were using and possibly not indicative of behavior across all strains? IE. would another strain exhibit differences in ester production, attenuation, flocculation, etc. at two different pitching temps? I would suggest this is quite possible. The apparent differences between two different strains of yeast in the same wort, fermented at the same temps, lead me to believe that it really isn’t possible to make blanket statements about yeast behavior. While these results may be valid as far as Super San Diego is concerned, the story could be quite different if another yeast were tested.
You raise a lot of interesting questions about this experiment. This is just one more I thought was valuable to consider.
Totally, this is why we need more people experimenting!!
This has been my experience too although anecdotal. I stopped caring the temp of the pitch a few years ago…getting close is good enough. I’ve also pitched “hot” on high gravity beers, they turn out fine as well. Overall I don’t think it much matters.
Another great experiment here. It might be true of lagers…let’s hold onto that for now.
One thought – for people trying to control temperature with a swamp cooler instead of a freezer, it may still be good advice to pitch low. On the occasions that I’ve used a swamp cooler, I’ve found that pitching low makes it much easier to manage fermentation temp than when pitching high.
Absolutely! I think I alluded to this in the post, if not, I meant to.
Whoops! I see that now, must have read too quickly!
You’re awesome! Thanks for actually testing these things, rather than just speculating and repeating speculation!
Again, Congrats for your initiatives!
May I have some comments,
1. I’ve noticed that you fermented both carboys with aluminion foil on the top, just like a yeast starter and, at the end of Diacetyl Rest, both carboys had air-locks. Is this your usual procedure?
2. At the beggining of fermentation, the warm-pitched carboy had much more Trub than the cold-pitched one. I’ve read your experiment on “to trub versus not-to-trub in Ales”. Didn’t you noticed any difference between the warm-pitched and the cold-pitched? In Laggers, the difference is huge (at least in my experience)
Cheers,
Luis
I suspect that this could be one of those things to stack the deck in your favor. Frequently you can get away with certain shortcuts with no issue, but overall it might make your process more prone to problems, should the rest of your process not be flawless. I’m guessing it might matter a lot more if you do not pitch enough yeast and they have to grow more/ ferment more per cell before the ferment completes. Ultimately, it is left to each brewer to decide what they can get away with, and more skilled brewers can probably safely take more shortcuts.
– Dennis, Life Fermented Blog
Really interesting! Thx again for the time you put in it, best blogg around! Salutes from Sweden!
I absolutely agree that pitching warm without temp control is a recipe for disaster, especially if you have a large pitch of yeast. Last summer I made a few beers where I couldn’t chill down much below 80, pitched a big slurry from a previous batch, and aerated thoroughly. Harsh fusel city, even though they ended up going into my 60-degree basement. Once I realized what was up, I started leaving them in the basement overnight before pitching, resulting in MUCH better beer.
If you do have the ability to properly control temperature with a fridge/freezer, you can probably get away with pitching warm, and maybe even benefit from it.
I almost never pitch into fully cooled wort. usually mid 20s-low 30s (C). Never found that it made the slightest difference for low-mid OG ales.
I liked the comment above that more skilled brewers can (and do) safely take more shortcuts–this definitely agrees with my experiences. My dad never rehydrated yeast or controlled fermentation temperature (other than putting it in the basement) and his beers were excellent.
Well, if you’re going to compare yeast vial instructions with the orthodoxy, you might as well do the same batch — half with a starter of 090 and half with just a vial dumped in 🙂 Since White Labs says you need a starter only for >1.070 wort , past-its-date yeast vials or lagering temps, I rarely make a starter (my brewdays don’t violate those rules), but I’ve always wondered if White Labs was protecting sales or giving good advice there. Perhaps both 🙂
PS, to reply to myself, I *have* read your post about starters. I just figured it would be interesting to exBEERiment it.
I have made a starter a few times, but usually don’t bother because I’m not making super high gravity beers and also because I live literally 2 miles from White Labs, so I can get pretty fresh vials. It has been in the back of my mind that perhaps I’m leaving something on the table by not doing a starter — and it certainly is a bit of fun mad scientist beer chemistry 🙂
Oh, a vial vs starter xBmt is on the list 🙂
Great experiment. If/when you repeat this for normal gravity ales, let me suggest using Nottingham dry yeast. I’ve never run across a yeast that behaves more differently with temperature (not even heffe yeasts). Fermented cold, I love this yeast (I too pitch at or below 64°F and use a ramped profile). In haste I’ve added rehydrated Notty to 78°F wort only twice, and the resulting beers were FAR more ester-y than I normally expect from this yeast. Fermentation chamber is a temp controlled fridge (STC1000+) in better bottles.
Thanks! I’m pretty much done with Notty, I used it in a few xBmt beers at many different temps and never really developed a strong liking for it. I can’t see repeating this one with a normal gravity ale for a bit, as I’m super curious about lager yeasts and high OG ale. Cheers!
I think the fact that you brewed ales and at the temps you fermented at wouldn’t have a big difference as both temps would produce some esters. With Lagers where even a slight amount of esters would be noticeable, the pitching temp will most likely play a bigger role in that as opposed to Ales. Good experiment just the same and it would be great to do it again with a lager and pitch one at 50 or below and the other pitching high at say 60+ and then drop the temp. I would expect to see a big difference in those beers.
That’s the plan!
Fascinating experiment. On the two occasions I got impatient and pitched when the wort was “close enough” to fermentation temperature, I ended up producing awful beer. Since then, I do whatever I can to get the wort cooler. There’s nothing more depressing than having to throw out 5 gallons of beer after you’ve patiently waited 4-6 weeks…
Great write up..thanks for your time on this…cheers
I pitched a pilsner with 2124 at 22 degrees. Waited too long for activity before crashing. The Beer was half done at 22 degrees by morning! Whoops. Crashed to 11 for the next 1/3. then Dyactyl rest for the last bit.
2 weeks later. Turned out great. No esters, No dyactyl.
Im amazed, and confused how I could bugger up ferm schedule this much and get a clean beer !
I can never recall which yeast company it is…I think Fermentis…or Danstar…but one of them actually recommends pitching ale yeast between 21-24C (70-75F), then holding that temperature “until visible signs of fermentation”, then dropping to your normal ferment temp (e.g. ~18C/65F)
So far I’ve brewed two extract lagers and 1 partial-mash porter. Both lagers only had about 2 gal of hot wort which chilled easily in a ice bath in the sink coupled with 2 gal of cold water mixed into the fermenter.
The porter was 4 gal of wort to which I added 1 gal of cold water to bring up to 5 gal while trying to lower temp in a large plastic bin full of ice water. After 30 min and having run out of ice I was at 80 degrees and pitched anyway and the beer turned out great.
I moved it into the cellar and fermentation started within 6 hours and the room temp was 66 while bucket temp was 79 on day 1. Bucket temp was 74 on day 2 and 66 on days 3-9. This was Wy1968.
I’m about to brew a belgian ale using Wy1214 and am planning on having a lot more ice handy because I don’t want a ton of estery flavors and would like to pitch at 70 and then cool to 62 for the first 5 days then gradually rise to 68 on days 6-9. I make big blocks of ice by filling plastic containers with water and putting them into the freezer 2 days before brew day.
Hey, as long as you like the beer you make, that’s what matters most. Cheers!
I pitch at room temperature for my lagers then set in keezer for fermentation without any ester formation except once. I had a high o.g. maibock 1.068 that was pitched with a big starter at room temp and took off fermenting with high krausen at 64f. My poor keezer couldn’t chill the lager down to its general target of 52f fast enough with an active fermentation already going and this was the one time I’ve experienced any ester formation with this wlp940 that I’ve used 20 plus times. The esters were still tasty in the maibock but unexpected.
As a new brewer (partial mash) I have wondered many times about something I notice you do in your process, which is wait quite a while for your wort to reach desired temperature (I see you use a wort chiller to significantly cool it down but then wait hours or even overnight for it to adjust the last few degrees). Everything I’ve read up until now has made me believe it’s super critical to get wort to pitching temp in a big hurry, which has been both tough and stressful for me, given my rather basic setup. Can you comment/guide me on this?
While the xBmt seemed to suggest it doesn’t matter as much as we thought on the homebrew scale, I still chill to my target ferm temp, viewing it as added insurance.
I regularly pitch at 26-27 Celsius (80 F) and then chill in chamber down to 19-20 C (66F). I just can’t be bothered chilling in chamber, taking the fermenter back out, pitching yeast and putting back. My fridge gets the pitched wort down fairly quickly (6 hours) but I’ve never had any problem with ales or even wheat beers. I agree probably not a good idea for those without good fermentation temp control or with lagers. That would be the real experiment, pitch at 80 and chill or pitch at 66…
Looked this up after making several “warm pitch” ales that were later temp controlled in a cooler. Very good feeling To finally silence this voice in my head. All the warm pitched beers turned out as expected and this experiment is the final nail in the coffin. Thanks for posting this & Keep up the good work!
Long time ago, but, for future readers…
I think the experiment is invalid. He did not pitch yeast, he pitched starters and apparently at ambient temps. The problem is, starters are already active and these were at the same temps so the temp of the wort is not really going to affect the activity – both will start heading for a temp set by yeast activity straight away.
White Labs said the cool brew would slow activity starting and that it didn’t shows this is not a proper test of cool pitching.
Honestly it makes sense scientifically. The proportion of sugars fermented in the first few hours is very small, escpecially if you consider that it coincides with the lag phase of fermentation. While in theory the beer may have slightly more esters, than if cold pitched, on the scale of a full lager fermentation (150 hours or so), I don’t reckon it is really significant. If anything I would share the opinion of the White Labs guy who said the warm temperature will help getting a vigorous fermentation and eventually getting a better attenuation (benifits outweight the risks).
The directions given by Fermentis for rehydration of dry yeast seem to support that view also: when sprinkling straight in wort, they recommend it to be at 20+ degrees (C), which is well above the optimum temperature for fermentation.
I think we cant emphasise enough the stress encountered by dry yeast at rehydration: the osmotic stress plus temperature stress at a moment when the yeast is very vulnerable.
Ale fermentation could be a different story as temperature control is more challenging when the fermentation gets going (and it’s quite early on).