A couple of months ago, I decided to conduct a very scientific experiment to measure the effects of fermentation temperature on a beer. Brulosopher, eat your heart out!
Of course, I am completely lying about the "very scientific" portion of my claim above. As I have documented before, I am not employing anything close to the level of scientific controls that Marshall uses - on the contrary, I am, in fact, a hack.
Just to recap, I decided to brew an extra large (seven gallon) batch of my Enchantress (a big Irish red ale). Marshall's findings that kolsch yeast really didn't seem to care about fermentation temperatures just didn't feel to me like they were super applicable to a lot of homebrewing - largely since that particular yeast is so clean and versatile. I, on the other hand, would be using WLP004 (Irish ale yeast), which - while it isn't known for being a super expressive strain - will certainly get a little fruitier than the kolsch yeast.
So, I brewed as normal, splitting five and a half gallons of wort into my normal 6.5 gallon glass carboy, then dumping the remaining gallon and a half into a two gallon plastic bucket. I did take great pains to continually stir my wort so as to ensure the most consistent mix of kettle trub possible, I carefully measured my yeast in an effort to hit roughly the same pitching rate, and I did my best to treat both batches to a similar level of oxygen injection. Of course, it is entirely possible that I goofed on any of these, or that the differing fermentor geometry had an unexpected influence on the final flavor of the beer. For the record, I seriously doubt that any of these factors influenced anything... but from a purely scientific perspective, I cannot be certain.
Nevertheless, I placed my carboy into my fermentation chamber (mini fridge) and dialed the STC-1000 to sixty-five degrees F, while the bucket was placed in my bathroom, where the ambient temp hovered between seventy and seventy-two degrees most of the time. I've had great success with this STC-1000 setup; I have yet to measure a temperature more than a half degree C (or, roughly, nine-tenths of a degree F) off of the target temp. On the other hand, with no cooling at play (and the exothermic activity of the yeast), I expected my bathroom batch to easily reach seventy-five degrees F, if not higher.
Both fermentors were showing visible activity when I got up the next morning. For the first forty-eight hours, my temperature controlled carboy was always within .2 degrees C (.36 degrees F) of my target temp. On the other hand, my bathroom bucket appeared to get as high as just shy of 77 degrees F for at least a short time. By the time I got home from work on the third day (post brew), both fermentors had slowed considerably in activity, and by the fourth day, they were done. However, I left them for several more days to clean up prior to cold crashing both at around 38 degrees F.
I ended up getting fairly lazy and distracted, and took nearly a month to bottle this beer; I suppose that you could say that I lagered it for a bit. However, it did seem to carb up fine, so no harm was done.
Yet again, you will notice that my findings are far from statistically significant; I *did* sample the beers using a blind triangle test, with my son pouring the beers for me (in another room to prevent me from knowing which was which)... but I obviously was aware of the nature of my experiment. With that said, it took me all of about three seconds to correctly identify the warm-fermented beer.
First off, the aroma was readily apparent - it had a stronger, fruitier smell to it, with almost a sickly note. Flavor was likewise noticeably different; the ambient temp beer had much more of a "homebrew" taste to it, with a harsher, more fruity flavor. I have repeated the tasting several times now, mixing up with cool and warm fermented samples, and I have yet to have any difficulty picking out the odd beer. To me, this is an open and shut case - the beer lacking in temperature control is clearly inferior.
Of course, I'm just one guy. To be fair, a brewer I really trust tried these beers - not in a triangle test, but on consecutive nights - and could not readily identify which was different. It is entirely possible that I am simply more sensitive to these esters than he is, or than your average bear is... but I don't view myself as having a particular sensitive palate. I will say that if I pull one of the warm-fermented beers out of the case, I enjoy it measurably less than the cooler fermented beer.
So, there you have my single data point. Do with it what you will; consider it, ignore it, reject it altogether. For my money, though, the traditional homebrewing lore was spot on, at least for this recipe and this yeast - the temperature controlled beer was noticeably better than the ambient temperature fermented beer. If it's all the same to you, I will continue to advise new brewers to obtain some method of reliable temperature control as soon as possible, as I continue to firmly believe that controlling fermentation temperatures - along with pitching an appropriate amount of healthy yeast - is the best way to see real improvement in the quality of one's beer.
Tags for this post: temperature, control, Irish, red, ale, experiment