When it comes to improving one’s homebrew, likely the most popular recommendation is to start controlling fermentation temperatures. Given the fact the first xBmt on this topic did not achieve statistical significance, I was curious to see how that might change under different conditions. In this go-round, I used a more characterful English yeast and fermented at temps a tad more extreme than in the first xBmt. Results are in!
im suprised! wlp002 that warm and really nobody detected any significant fruity esters? this is very interesting indeed Marshall.
Edit: i’ve got the equivalent wyeast 1968 going right now in an ESB. pitched at 63F, held 65-66F 48 hours and letting it rise up to 70F to finish.
Tell me about it! In the past, I’d told myself that fermenting with 002 at anything above 68˚F produced crazy esters, in fact I’ve told others I’d even experienced this… apparently erroneously. I’ve been finishing the last bits of both of these kegs and they truly are way more similar than difference, both are perfectly enjoyable.
I wonder how much of the “temp control = better beer” comes from minimizing temperature swings? My fermenting closet only experiences two degree swing on a bad day, and I’ve never had issues fermenting British ales up to 72 degrees there.
It’s be interesting to redo the experiment, and make the experimental group undergo a temperature swing, say 74* during the day to 66* at night.
i’m curious about something. do you think perhaps that starting a fermentation warmer and holding it there- in your case about 76F produces any different results than a beer pitched cooler and allowed to rise rapidly? e.g. pitched at 64-65F and then when active fermentation starts you don’t manage temp control and it rises rapidly to the low to mid 70’s? whenever I’ve had issues with unwanted esters, its been a result of this.
just thinking out loud :
Interesting results! My attempt to explain:
If you pitch enough good healthy yeast, fermentation temperature doesn’t matter so much. Try this same experiment with a poor pitch of old yeast, and you will get very different results.
Also, I am absolutely certain that selection of the specific yeast strain can make all the difference. Try the same experiment with a hefeweizen yeast or Belgian yeast, for instance, and you will get two entirely different beers, no matter what your pitch rate.
But USUALLY… if you pitch a lot of healthy yeast, this can make fermentation temperature closer to a moot point.
I agree with all of this. Definitely strain dependent, too. Doesn’t matter how much healthy 1214 you pitch, for example - that stuff is crazy temp sensitive.
I wonder if the recipe choice had something to do with this, in particular the relatively low OG. Low-gravity wort is generally considered less stressful to yeast, so that may help in minimizing the difference between the two beers. I’m wondering if this was repeated with an ESB in the 1.060’s if the gap between the two brews would be more noticeable.
Another great xBmt, Marshall! Thanks for sharing.
Would over pitching cause a lack of malt character in any instance? Or just last of yeast character?
All great points! I’m getting to the point where I think multiple variables play off of each other. So, for example, low pitch rate + controlled ferm temps + low OG will likely work out fine; high pitch rate + uncontrolled ferm temp + moderate OG will likely be fine too; but low pitch rate + uncontrolled ferm temp + high OG may be significantly flawed.
I definitely have xBmts planned to test this
Ding ding ding! I was thinking the same thing. My guess is that the biggest difference would be attenuation. Those repeated drops in temp are most likely going to send the swinger yeast into dormancy sooner than the steady controlled yeast.
I agree Marshall. And think how this compares with the typical new home brewer who is about 4 or 5 batches into the hobby. Showing up with a high gravity beer that they pitched one smack pack or tube of yeast right off the shelf, no starter, pitched at about 70º and sat in a spare bedroom 78 in the day 65 at night. Airlock quit bubbling after 7 days so they bottled it… we would have lots of advice to give on using sugar, making starters, taking gravity readings rather than going by the airlock, but most of us would point to better temp control as the one single thing that would improve it.
Hey, you described my first 5 batches exactly! Although I don’t do high gravity beers and I’d let mine sit in the primary for 4 weeks before bottling - not sure that did much to help most of those batches.
From exBEERiment article: “Along with many others who’ve been in the hobby for awhile, I’ve stated multiple times that one of the absolute best things a homebrewer can do to make better beer is control fermentation temperatures.”
Yes, you still are controlling the temperature - just at a higher one. I think the idea of pitching healthy yeast in at least ballpark close to the “right” numbers at a reasonable, constant temperature with proper oxygenation has merit.
Nice xBmt - keep it up.
The right number of cells to pitch is less for a British ale than if you were making a clean American Ale. Friends at a local Brewpub use WLP-022,a nod make fruity estery ales at a low pitch rate and double it if they want a cleaner more American style ale. Seems the is even something written on this.
Would it be worth the time to do an experiment on temp at a low pitch rate?
http://byo.com/grains/item/1717-yeast-pitching-rates-advance-homebrewing
I think the comments about the gravity being very low is apt. IMO, single variables don’t seem to make as large of an impact as we’d all expect, but I do think they make a bigger impact at higher gravities.
After all, we make starters at ~1.040 OG because it’s optimal for the yeast for a variety of reasons, a wort with gravity ~1.040 is basically just a giant starter
FWIW, I just made an ESB w/ a big ol’ pitch of WLP022 and I still got plenty of ester character. It was like cherry preserves smeared on toast!
Hell yeah!
It can be fairly clean with a big pitch, how big, I have to ask.
I do like that yeast. From a closed brewery in Clemsford England, a guy in our club had brought some back and gave White Labs a sample.
+1 - temp stability vs. temp control?
Home brewing is chock-full of practices that are not supported by science. A while back, I posted that having to ferment ales below the yeast propagator suggested temperature range in order to achieve an off-flavor-free beer was a sign of poor sanitation and/or yeast management. That information was accepted about as well as would a lard omelette by many forum members.
The cold hard reality is that most domesticated brewing yeast strains have to experience stress before they throw tons of metabolite trash. Stresses can be as simple as inadequate aeration, or shear stress from being propagated on a stir plate. Large temperature swings can also cause stress.
Pitching a small amount of yeast into a high gravity wort creates a two-fold problem. The first problem is osmotic pressure. The solution on the outside of the cell wall has a higher solute content (i.e., the solution is hypertonic), which results in water being drawn out the cells. The loss of water results on the loss of turgor pressure, which, in turn, results in cell shrinkage and possible implosion. The cells that do not implode experience difficulty passing nutrients and waste products through their cell membranes.
The second problem that one experiences with high gravity brewing is that it is more difficult to dissolve O2 in high gravity wort than it is in low gravity wort; hence, it is more difficult to grow a large culture from a small number of yeast cells when propagating in high gravity wort than it is when propagating in lower gravity wort. As yeast cells shunt O2 to the respirative metabolic pathway for the synthesis of ergosterol and unsaturated fatty acids (UFAs), ergosterol and UFAs make the cell membrane more pliable, pliable membranes are needed for the passage of nutrients and waste products as well as the ability to resist the effects of osmotic pressure, and the mother cells that are in existence when the O2 is still in solution share their ergosterol and UFA reserves with all of their children, it is easy to see how starting with a small number of yeast cells could result in a fermentation where the cells are stressed for the duration of the fermentation.