It’s volume 2 of our series on essential brewing knowledge that I wish I’d known when I started. Sort of like me making massive mistakes in brewing so you don’t have to!

Today, we’ll be tackling temperature, and although not something as tangible as say, yeast, nonetheless super-important.

If you’re new to brewing, you need to know about some jargon that brewers sometimes use that refers to temperature: The hot and cold side of brewing.

By hot side, we mean the process of mashing and boiling while by cold side, we mean the fermenting part of brewing. Both sides are all about getting to the right temperatures because as it turns out, temperature control is pretty vital to making good beer.

Let’s start at the beginning. No, not when the Earth was still unformed, a little later. Let’s start with temperature and mashing and steeping grains.

Mashing and steeping temperatures

If you’re brewing all grain recipes, you’ll need to mash your base grains to produce wort. And mashing is all about maintaining the correct temperature for the right amount of time.

For most beginning brewers, you really only need to keep two bits of temperature information in mind when it comes to mashing: higher temperatures produce fuller bodied beer, and lower mash temperatures produce lighter bodied beers. That’s because the different enzymes responsible for producing fermentable and non-fermentable sugars work best at different temperature ranges.

The enzymes responsible for producing mostly fermentable sugars work well at lower mash temperatures, around 64 degrees Celsius (174 F). If you keep your mash at this temperature for 60-70 minutes, you’ll be producing more fermentable sugars in the wort. This will have two effects:

  1. Your beer will finish dryer because more sugar would have been converted into alcohol
  2. Your beer’s body will be lighter, because of less residual (i.e. non-fermentable) sugar in the final product

To achieve this mash temperature, you’ll have to account for the grains cooling down the mash water, so you’ll have to start a few degrees higher, about 71 degrees Celsius (160 F).

Higher mash temperatures inhibit the production of fermentable sugars, thus leaving more residual sugar in the beer. This also results in a more full-bodied, less dry-finishing brew. If you’re aiming for that, mash in at 76 degrees Celsius (169 F) to achieve a resting temperature of around 69 degrees Celsius (156 F).

Irrespective of the mash temperature you’re after, don’t go over 76 degrees Celsius (169 F). The higher your mash temperature, the more inactive those precious enzymes become until ultimately, they denature and conversion comes to an abrupt halt. Which could be bad if you’ve just started.

Doing this at the end of the mash is okay, and known as mashing out, when the brewer purposefully stops the mashing process to achieve specific goals.

For extract brewers who steep specialty grains, you’ll need to achieve a water temperature of 60-68 degrees Celsius (140-154 F). The important thing to remember is to not go over 70 degrees Celsius (158 F). Once you reach that, the likelihood of extracting unwanted flavors from your grains increases, and you don’t want that, do you?

Steep your grains for 30 minutes at the right temp, and you’re golden!

Boiling your wort

It might seem obvious that boiling your wort requires, well, duh, boiling water temperatures. That’s correct, but one thing to keep in mind is that higher altitudes mean lower boiling temperatures. So, if you’re next to the coast (you lucky devil, you), water will reach a rolling boil at around 100 degrees Celsius (212 F).

But, if you’re higher up, things change. For instance, where I live, on the Eastern Plateau of Southern Africa, water boils at 94 degrees Celsius (201 F). That’s a pretty big difference (to calculate your hometown’s boiling temp, check out this site).

What does that mean?

Well, for one, the lower your boiling temperature, the less hop utilization you’ll have. Also, you have to ensure that you really do have a rolling boil. Just simmering the wort ain’t going to help! That way lies poor hops utilization, murky beer, and worse, the dreaded cooked-corn off-flavor of DMS.

The cold side: chilling

Once you’re done boiling your wort, it’s time to chill. And I don’t mean cracking a cold one and going to watch Stranger Things (although it is a really good show, that).

You’ve got to bring your near-boiling wort down to a reasonable temperature for yeast to function in. That’s around 20-30 degrees Celsius (68-86 F). The quicker, the better. Achieving a rapid cool-down helps with clarifying your beer (the so-called cold break) by pushing out of suspension various proteins that would otherwise end up in your beer.

It also ensures that your beer has minimum contact with possible contaminants before you pitch your yeast. As discussed in other posts, keeping things clean is a really, really good idea.

So, to make that happen, you’ll have to use a big old ice bath, or more sophisticated devices like a counterflow or immersion wort chiller. Whatever you do, don’t rely on mother nature to to the job for you. Unless you live in Antartica. Which is pretty cool. Pro tip: don’t put the electric space blanket on the frozen alien monster. Just saying.

The cold side: fermentation

Controlling fermentation temperatures is essential to good beer. Various off-flavors (e.g. acetyldehyde) come out to play when your fermentation temperatures are all over the place.

Fermenting too warm (e.g. above 28-30 degrees C; 82-86 F) also risks the formation of fusel alcohols, which makes your beer heavy, boozy and can result in a really mean hangover-type feeling that is just no fun at all. In fact, if you’ve ever felt like you’ve gone for a friendly little sparring session with Tommy “The Hitman” Hearns after drinking someone’s homebrew, you probably know what fusels are all about.

The main aim is to keep your fermentation as steady and cool as possible. For most ales, you’re trying for a range between 16-22 degrees Celsius (61-71 F) while for lagers, 7-14 degrees Celsius (45-57 F) will work. Once you achieve that range, stay there. The best method is to covert an old fridge into a fermentation chamber using an override thermostat. But that’s pricey.

A cheaper alternative is to put your fermentation bucket inside a larger container filled with large ice blocks that you change periodically. This takes practice and experimentation but can be very effective.

I’m not going to lie: maintaining fermentation temperature is really difficult for homebrewers, who mostly rely on ambient temperature for fermentation. So investing in a fermentation solution like a converted fridge is really not a bad idea, especially if you live in warm climes.

Well, that’s all for now, folks! I really do wish you wonderfully stable, well controlled (at least temperature-wise) brewing sessions ahead.

Now go make some beer.


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