Brew Tips #14: Temperature Control
This has to be one of the most interesting topics in home brewing. Despite being readily considered one of the most important areas/factors, there appears to be very little research here (comparatively speaking at least). It is also the one which I find often leads to the most potential misinformation and a wide array nonsense.
Is temperature control important? Definitely. To a point. When I said that there is very little research here, I want to be clear, where the research tends to be lacking is not whether or not there are differences in beers fermented at different temperatures. There absolutely is. In fact, these differences are the basis of how many yeast strains are sold. What isn't really covered is what that means to the home brewer.
First question. If a recipe says to ferment using US-05 at 18C does that mean 18C ambient or 18C in the middle of the wort? A quick bit of research will show that in general temperature recommendations should refer to the temperature in the middle of the wort. But, getting that temperature requires a sterilized thermometer in the fermenter. Most home brew kits don't include a fermenter with a probe or a proper opening for one. In addition to that, to maintain that temperature would require that the probe be connected to a temperature control module. Many people have temperature control modules. But I would doubt it is a majority. And I would doubt a majority of them have the probe rigged up inside of the wort.
This would mean that a lot of people that post these recipes are either giving the ambient temperature, or perhaps even just shooting in the dark. Which also means... we don't know the actual temperature the wort fermented at.
It also means that in those cases, we can assume that the temperature wasn't constant. People rant and rant about how an active fermentation can raise temperatures by 6-8F. This means that at any give point in time, the wort will be between 0 and 8F warmer than the ambient temperature. It will rise as fermentation picks up and lower as it slows. Put a little more subtly... the temperature fluctuates.
I guess my point would be that true temperature is really not attainable. Even with the temperature control module and the probe in the wort, there will still be areas between the probe and the wall of the container that fluctuate. And temperature control modules require that the change in temperature be over a certain threshold before they kick in. The temperature swings may be smaller, but they are still present. Of course, at these levels any differences are probably imperceptible, but the point remains.
So, for the average home brewer, what is missing is a general rule of thumb like "keep your ambient temps 4F cooler than your target temp" or "for ever 5G keep the ambient temps another 2-6F cooler than your target temps". Frankly, I am shocked to have never stumbled across any such logic. For what is widely held to be second important only to sanitation there is little to no information provided to the home brewer.
The next question I would have is; is it better to aim for the target temperature using an somewhat unreliable method of cooling, or is it better to eschew cooling and let it sit in a stable ambient environment?
What is yeasts sensitivity (in general) to temperature swings. If ambient fluctuates by more than X degrees per Y hour(s) the yeast will become stressed enough to noticeably impact your beer. Such a value must exist. We know those with highly accurate cooling processes still allow the wort to fluctuate +/- 1F, and on a fairly regular basis. Heck, we also know that despite the existence of these rules of thumb that there really aren't any home brewers complaining all that often about their beer quality.
So, while I may not have the big answers, I think I can say this; while temperature control can (and will) impact your beer. It generally seems to be on acceptable levels. This isn't to say that the differences aren't or won't be noticeable. It is more to say that unless your environment is excessively warm or excessively cold that you will make beer and adequate beer at that. With that as a starting point, you can always adapt recipes, including yeast strains, to change the beer more to your liking.
I would wager that most people who post recipes online use some sort of active cooling for their beer. So, if you want your beer to turn out as close to the recipe as possible you probably need it. But since you've probably never tasted any of these beers in person... well, you wouldn't notice, even if you had.
Also, it is worth noting that most brewers that post online actively don't often work anywhere near the posted acceptable ranges for yeasts. There are a few who do test batches on rare occasion and a few who have "war stories" about a batch they lost control of. But even then, you generally find them claiming that the beer was still good, or in some cases even difficult to notice the difference. While I'm sure PLENTY of home brewers work within these ranges, and regularly, they aren't the people posting online. And this is part of the reason the information online is lacking.
As usual, unless there are some extremes you will probably end up making beer. If you can successfully and repeatedly make beer, then you can tweak the recipe. There are plenty of things you can do to adjust the outcome of a beer. There are more and less fermentable sugars you can work with to adjust body. Hops, grains and yeasts (in addition to temps worked at) will affect flavors and smell. Aging also plays a role, especially if bottle or cask conditioned.
Is temperature control important? Definitely. To a point. When I said that there is very little research here, I want to be clear, where the research tends to be lacking is not whether or not there are differences in beers fermented at different temperatures. There absolutely is. In fact, these differences are the basis of how many yeast strains are sold. What isn't really covered is what that means to the home brewer.
First question. If a recipe says to ferment using US-05 at 18C does that mean 18C ambient or 18C in the middle of the wort? A quick bit of research will show that in general temperature recommendations should refer to the temperature in the middle of the wort. But, getting that temperature requires a sterilized thermometer in the fermenter. Most home brew kits don't include a fermenter with a probe or a proper opening for one. In addition to that, to maintain that temperature would require that the probe be connected to a temperature control module. Many people have temperature control modules. But I would doubt it is a majority. And I would doubt a majority of them have the probe rigged up inside of the wort.
This would mean that a lot of people that post these recipes are either giving the ambient temperature, or perhaps even just shooting in the dark. Which also means... we don't know the actual temperature the wort fermented at.
It also means that in those cases, we can assume that the temperature wasn't constant. People rant and rant about how an active fermentation can raise temperatures by 6-8F. This means that at any give point in time, the wort will be between 0 and 8F warmer than the ambient temperature. It will rise as fermentation picks up and lower as it slows. Put a little more subtly... the temperature fluctuates.
I guess my point would be that true temperature is really not attainable. Even with the temperature control module and the probe in the wort, there will still be areas between the probe and the wall of the container that fluctuate. And temperature control modules require that the change in temperature be over a certain threshold before they kick in. The temperature swings may be smaller, but they are still present. Of course, at these levels any differences are probably imperceptible, but the point remains.
So, for the average home brewer, what is missing is a general rule of thumb like "keep your ambient temps 4F cooler than your target temp" or "for ever 5G keep the ambient temps another 2-6F cooler than your target temps". Frankly, I am shocked to have never stumbled across any such logic. For what is widely held to be second important only to sanitation there is little to no information provided to the home brewer.
The next question I would have is; is it better to aim for the target temperature using an somewhat unreliable method of cooling, or is it better to eschew cooling and let it sit in a stable ambient environment?
What is yeasts sensitivity (in general) to temperature swings. If ambient fluctuates by more than X degrees per Y hour(s) the yeast will become stressed enough to noticeably impact your beer. Such a value must exist. We know those with highly accurate cooling processes still allow the wort to fluctuate +/- 1F, and on a fairly regular basis. Heck, we also know that despite the existence of these rules of thumb that there really aren't any home brewers complaining all that often about their beer quality.
So, while I may not have the big answers, I think I can say this; while temperature control can (and will) impact your beer. It generally seems to be on acceptable levels. This isn't to say that the differences aren't or won't be noticeable. It is more to say that unless your environment is excessively warm or excessively cold that you will make beer and adequate beer at that. With that as a starting point, you can always adapt recipes, including yeast strains, to change the beer more to your liking.
I would wager that most people who post recipes online use some sort of active cooling for their beer. So, if you want your beer to turn out as close to the recipe as possible you probably need it. But since you've probably never tasted any of these beers in person... well, you wouldn't notice, even if you had.
Also, it is worth noting that most brewers that post online actively don't often work anywhere near the posted acceptable ranges for yeasts. There are a few who do test batches on rare occasion and a few who have "war stories" about a batch they lost control of. But even then, you generally find them claiming that the beer was still good, or in some cases even difficult to notice the difference. While I'm sure PLENTY of home brewers work within these ranges, and regularly, they aren't the people posting online. And this is part of the reason the information online is lacking.
As usual, unless there are some extremes you will probably end up making beer. If you can successfully and repeatedly make beer, then you can tweak the recipe. There are plenty of things you can do to adjust the outcome of a beer. There are more and less fermentable sugars you can work with to adjust body. Hops, grains and yeasts (in addition to temps worked at) will affect flavors and smell. Aging also plays a role, especially if bottle or cask conditioned.
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