Just how important is your fermentation temperature in homebrewing? I came across a startling result from an experiment reported in the new homebrewing book Yeast, by Jamil Zainascheff and Chris White.
Chris White is the President of White Labs, a brewer’s yeast manufacturer. White Labs conducted a study in which two of the exact same ales were brewed, except one was fermented at 66°F and one at 75°F. They then tested for the difference in flavors.
Most of the flavors that we’d consider “off-flavors” showed a moderate increase, but what was really startling was the increase in acetaldehyde, which gives beer that green apple flavor. Its concentration was 8ppm in the 66°F beer, but 152ppm in the 77°F beer. So a 9 degree increase in temperature, but the acetaldehyde was 19x higher!!
Controlling Fermentation Temperatures
I’ve known for some time now that fermentation temperatures are important, but over the past year have realized just how important they are. Examples like the one above, plus other information in this book, advice from other brewers, and most importantly, my own experience has taught me that if you want to make the best beer possible, you need to nail your fermentation temperatures.
But that requires equipment.
Putting the carboy in the back of your closet and praying isn’t going to cut it. Even if your house stays at a cool 66°F, during the height of fermentation your beer can easily go up 10 degrees because of the exothermic reactions. And 76°F is going to produce more flavors that will rob your beer of a clean taste.
The good news is that most of these flavors are produced during the first 72 hours of fermentation, so you don’t need to maintain the cooler temperatures the entire time the beer is in the fermenter. In fact, it is beneficial to let the temperature rise after fermentation so they yeast can fully attenuate and clean up some of those flavors produced during the height of activity.
Those first 72 hours is where the magic happens though, and we need to make sure we hit the correct temperatures.
Temperature control gadgets truly run the gamut in the brewing world. From a chilly corner in a homebrewer’s basement, to glycol cooling jackets on a commercial brewery’s stainless steel conical tank, to everything in between. When it comes to controlling temperatures, there is certainly more than one way to skin a cat, but I’m going to look at the most practical options for homebrewers.
The swamp cooler is one of the cheapest and easiest ways to cool your fermenter. There are a few different swamp cooler variations. Most consist of a container to hold water and require the brewer to continuously rotate frozen water bottles for cooling. A t-shirt over the carboy can be used to draw water up, and some people point at fan at the fermenter to get the evaporative cooling effect.
As you can read in my swamp cooler experiment, keeping consistent temperatures is the biggest problem. Large temperature swings are inevitable unless you are able to rotate bottles in every few hours. Even if you had that kind of freedom it would be a pain in the ass.
A more advanced swamp cooler I’ve seen uses an Igloo cooler with a foam top. This is a huge improvement because insulation is the weak point of the swamp cooler. YooperBrew over on HomebrewTalk has has one of these swamp coolers which she calls “The Lagerator”. This is a future project for me.
- Good way to combat the heat of the summer
- Ability to get beer to ideal temperature range
- Labor intensive because you must frequently rotate out frozen water bottles
- Difficult to maintain temperatures
- Lagering is very difficult
Son of a Fermentation Chiller
This contraption is one of the most common homebrewer DIY projects out there. Commonly referred to as the “Ken Schwartz Son of a Fermentation Chiller,” it seems that Mr. Schwartz originated this thing. Here is his document which is often referenced for plans.
How does it work? Schwartz say it best,
The Fermentation Chiller is an insulated box which uses ice, a thermostat, and a small fan to accurately regulate the temperature of a fermenter. While simpler insulated boxes and other simple temperature-management techniques often work reasonably well, they can’t regulate the temperature; they can only cool to “some point” below ambient, which changes as the ice melts.
So basically, you place gallon jugs of ice into the “ice chamber” and when the thermostat says it is time for cooling mode, the fan cuts on and blows cold air into the fermentation chamber until it is at the desired temperature.
The obvious drawback about this is the work involved. The other is that it still involves rotating bottles of ice, but it is much more infrequent (every couple of days) vs. the swamp cooler (every few hours).
- Cheap (~$70) compared to a freezer or refrigerator
- Small footprint (2′x3′) and lightweight
- Very low cost of electricity
- A bunch of upfront work needed, not to mention craftsmanship and tools
- Requires exchanging of ice
For those looking for a more automated approach, you will want to go with a chest freezer or cooler. I personally prefer chest freezers because their design makes them more energy efficient (the cold air stays inside when the door is open). Their drawback is that it takes more lifting to get fermenters inside.
These devices must be used in conjunction with a thermostat to control the temperature, which usually cost between $60-$100. Prices for the chest freezers vary based on size and condition. You could easily find a small cheap one on Craigslist for $50, or pay $400 for a large brand new model. The added benefit of this option is that they can double as kegerators. That’s a big plus in my book
- Very little construction and maintenance involved
- Keeps the most accurate temperatures
- Can double as a kegerator
- Expensive ($100-$300 for the appliance and $60-$100 for the thermostat)
- Large and difficult to move alone
- Higher electricity cost
Temperature Controlled Conical Fermenter
At a starting price of $1,800, I’m not going to give much attention to these. Just revel in its awesomeness for a minute and think to yourself, “One day…”
So where do I stand in this sea of options? Unfortunately I’m not as sophisticated as I would like. I’m still using my ole’ blue tub as a swamp cooler, which allows me to mitigate high temperatures, but not get the consistency and accuracy that I would like.
The chest freezer fermentation chamber is my goal. Since mine bit the dust on my move to Denver, I’m watching Craigslist like a hawk for a good deal. Once I find one, you can expect a full report on how it turns out.
Do you practice temperature control on your fermentations? What do you use?