My last batch of session ale was slightly over pitched with re-hydrated S-04 and spent the first 3 days around 72f. Fermentation took off like a rocket and was at my expected FG (OG1.039-FG1.009) within 72 hours. A comment by another member got me concerned about the acetaldehyde that the warm temperatures may have produced so I started digging to find out how more about this compound and how to avoid production in the future. Mostly because I dont have the ability to control temperatures outside of 68-75 ambient and assuming primary is warmer 70-78. My mistakes aside (over pitching plus warm temperatures) I found a very interesting research article from a time long ago that measured acetaldehyde during different phases in the brewing process. In short this study quantifies the increase of acetaldehyde from the bottle conditioning process which furthers what I have read and heard from other homebrewers regarding the benefits of kegging and the ability to retain a flavor; or at least in this case not contribute to additional off flavors. What was surprising was that once the compound was formed there was little if any reduction over time. http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1971.tb03405.x/pdf Now I will be taking this newly founded info back to the wife to explain the benefits of and reduction of carcinogens when investing in a kegging system.
I would probably try to use a different yeast than s-04 if you can't lower temps or most likely you will be disappointed every time. I haven't found that particular yeast to be very forgiving at all when it comes to higher temps. You could look at the swamp cooler method or simply placing your fermenter in a water bath submerged a bit above the wort line to help keep things cooler and a bit more constant. It's helped me in the past anyways.
Yes I will be doing that. s-04 worked for me in the dead of winter when the house was 65f but now I have to start thinking seasonally. I see many of the belgian ale stains have temp ranges up to 78 or 80f. Might give those a try. With the bath, do you use tap water?
Yeah, S-04 might not only be prone to acetaldehyde production, but it also throws a more fruity, ester-rich flavor profile of it's own when the temps spike. Overpitching will actually help with this, being that the yeast has no need to reproduce and isn't "stressed" as much by the higher temps. It's usually accepted that US-05 is a little more tolerant of temps into the low 70s. That might be an option. Generally, I keep ambient at 62-ish for S-04 and 66-67 for US-05. And I'm using a water bath in a fridge tank with a temp control so that the thermal mass in the water is nearly the same as the wort, keeping the wort temp very close to the set point.
