Story by Forrest Whitesides.
If there’s one thing that brewers of all stripes are nearly militant about, it’s fermentation temperature. The classic rule of thumb for the vast majority of ales is 68 °F (20 °C), with many preferring the low-to-mid 60s °F (around 17 °C) to help create a clean yeast flavor profile. This is sage advice for the typical brew project. But sometimes you can disregard the old paradigm and embrace warmer fermentation temperatures. Don’t fear the 70s °F (around 24 °C). . . or maybe even the low 80s °F (around 28 °C). I’ve brewed some excellent beer that completed most of its fermentation in the 76–82 °F (24–28 °C) range, and a few have even gone as high as 85 °F (29 °C). The tricks to making good beer at high temperatures basically boil down to three things: yeast strain selection, extended primary fermentation time, and bulk cold aging.
The most obvious choice for a high-temperature yeast is one of the various Belgian-style strains, but there are some others outside this category that will work as well. The key is to choose a yeast that is rated for higher temperatures. Low diacetyl production is nice as well, but this isn’t super-critical. The table at the end of this article lists some of the yeast strains that are good candidates, and their temperature range.
The list in the table is not exhaustive. I have also had good luck with Safbrew US-05 in the 75–78 °F (24–26 °C) range. And let’s not forget that fermenting critters besides the familiar Saccharomyces cerevisiae are also good candidates for high temperatures. Brettanomyces, Lactobacillus, and Pediococcus strains all work pretty well in the warm environments. Maybe it’s time to finally man up and make a lambic or some other funky brew!
One of the upsides to high fermentation temperatures is that primary fermentation begins very quickly (sometimes in as little as an hour) and is also completed very quickly (sometimes as soon as within 48 hours). But that is where the high-speed part of the process ends. High temperatures will almost always yield more intense flavors from the yeast: high levels of esters and phenolics, but also more-than-usual amounts of fusel and wood alcohols, as well as diacetyl. The esters and phenolics can be a good thing, especially if you like Belgian-style brews, but higher alcohols and diacetyl are almost always bad things.
To help offset the bad side of warm fermentation, I have found that leaving the fermented beer on the yeast cake for an extended period to be very helpful in almost all cases. Once the primary fermentation action is complete (often 2-3 days at high temperatures), let the beer sit on the cake for an additional 2-3 weeks. If the resting temperature is above 75 °F (24 °C), do not go beyond 4 weeks (to help avoid autolysis). During this time, the yeast will reabsorb some of the diacetyl. Additionally, suspended particulate in the beer will have ample time to flocculate.
After at least 2 weeks on the yeast, transfer the beer to a secondary container (another carboy or a keg, for example), and cool it to serving temperature. A kegerator with some extra space is an ideal spot. This process is best carried out with kegging as the end method for dispensing (but can be done if bottling is desired as well). To minimize the change of oxidation, I recommend purging the keg head space with carbon dioxide (CO2) before beginning the cold bulk aging process. Keep the beer at serving temperature for as long as possible before tasting. I recommend at least a month; longer if you have the patience. It is during this time that the “hot” aftertaste from the fusel alcohols and other undesirable flavors begin to mellow. Time (and cold) heals most wounds with hot fermented beer, it seems.
Keep in mind that this process is not going to turn out crisp, clean-tasting ales. It’s going to be fruity, spicy, and quite possibly funky. Although there is virtually zero “lag time” at the beginning of fermentation, and even though fermentation is completed quickly, pushing the yeast to its limit does create big and sometimes surprising flavors. Expect exaggerated notes of banana, mango, clove, and bubblegum, as well as maybe hints sour and possibly even some flavors that could be described as “horsey.” In the right amount and in right beer, these flavors and aromas can be wonderful. (For tips on how to curb the production of esters and other yeast-derived characters in a warm fermentation, see the Summer Brewing Tips article.)
High-temperature brewing is not for the faint of heart, but it can turn out some very complex and unique beers. And it’s perfect for the hot weather months. Experiment and enjoy.
Forrest Whitesides is a regular contributor to Brew Your Own magazine and Final Gravity Podcast.
Table 1. Yeast Strains for High Temperature Fermentations
Here are some yeast strains that can ferment at high temperatures without producing unhealthy amounts of higher alcohols (fusel oils).
White Labs WLP550 (Belgian Ale) — 68–78°F (20–26 °C)
White Labs WLP566 (Belgian Saison II yeast) — 68–78°F (20–26 °C)
White Labs WLP568 (Belgian Style Saison Ale Yeast Blend) — 70–80 °F (21–27 °C)
White Labs WLP065 (American Whiskey Yeast) — 75-82 °F (24–28 °C)
White Labs WLP655 (Belgian Sour Mix 1) — 80-85+ °F (27–29 °C)
White Labs WLP665 (Flemish Ale Blend) — 68-80°F (20 –27 °C)
Wyeast 1214 (Belgian Abbey) — 68-78° F (20-24° C)
Wyeast 1388 (Belgian Strong Ale) — 64-80° F (18-27° C)
Wyeast 3724 (Belgian Saison) — 70-95 °F (21-35 ° C)
Wyast 3725 (PC Biere de Garde) — 70-84 °F (21-29 °C)
Wyeast 3763 (Roeselare Ale Blend) — 65-85 °F (18-30 °C)
Wyeast 3787 (Trappist High Gravity) — 64-78 °F (18-25 °C)
Wyeast 3822 (PC Belgian Dark Ale) — 65-80 °F (18-27 °C)
Fermentis Safbrew T-58 — 12-25°C (54-77 °F)
Fermentis Safbrew WB-06 — 12-25°C (54-77 °F)