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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| Read More |

18 Ideas to Help Simplify Your Brew Day

7 Considerations for Making Better Homebrew

List of completed exBEERiments

How-to: Harvest yeast from starters

How-to: Make a lager in less than a month

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