Most of us are reveling in the amazing weather that has finally come after a very long and very snowy Alberta winter. But...with that hot weather comes more than a suntan and the need for an ice cold, lawnmower beer... it brings a challenge that brewers need to consider if they are going to continue to make great beer at home throughout the summer months.
Now, if you've been to one of our classes or have talked for ANY amount of time with us about brewing you'll remember us saying that temperature accounts for two thirds of the most critical variables in your brew day and includes the mash temperature and the fermentation temperature (the third critical variable of course being sanitation). Today, the focus is going to be on fermentation temperature and how it can make or break your beer!
Anyone that has brewed beer before knows that the four main ingredients used are water, malt, hops and yeast. Each ingredient contributes an important part in flavouring the beer, but the one that can most significantly change a beer's flavour is YEAST. Now, because yeast is a living organism, it should come as no surprise that they are affected by temperature fluctuations and it is for this reason that every package of beer yeast includes a "recommended" fermentation temperature range.
In general, most lager yeasts perform best at a temperature range of between 48 F and 56 F (9-13 degrees C) and most ale yeasts do their best work between 60 F and 72 F (15-22 degrees C). Now, although it is true that some yeast strains can produce desired flavours (esters) like the coveted banana/bubble gum flavour in Hefeweizens when fermenting above the high end of that temperature range, staying within the recommended temperatures will ensure you are not encouraging the development of "solventy", higher order alcohols that can leave your beer undrinkable.
Acetaldehyde (which presents itself in your beer as a "green apple" flavour) in particular, is formed in excess when the fermentation temperature is too high in the first critical days of fermentation. This is one of THE MOST COMMON "off-flavours" identified in home brew and although there are other factors that contribute to the creation of acetaldehyde (under pitching of healthy yeast, poor aeration, oxygenation and even adding beer finings too early making the yeast flocculate before fermentation is compete) it is absolutely preventable.
So why does this matter to you today? Because as I sit in my backyard writing this up over my lunch hour, I am enjoying the 28 degrees C heat and I know that without my air conditioner inside, it would be kicking my ambient house temperature up and moving my fermentations over the recommended temps. So what can you do to keep your fermentation temps "in range" during summer heat waves? Here are a few ideas:
Find a spot in your house that is cool enough to ensure you will NOT exceed the maximum recommended fermentation temperature, but that is also not too low (yeast will get sluggish and "go to sleep" if the temperature is below the recommended range too) and that does not fluctuate a lot. You're most likely going to consider your basement at this time of year because it is so much cooler than everywhere else...if this is you, monitor the temperature to ensure you are not too cold as well.
If you're struggling to keep the fermentation temps down with just the ambient house temperature (and you're brewing on a budget), try wetting a small towel and wrapping it around the fermenter jug and hit it with a fan to continuously add cooling.
If you have the budget for it, your BEST bet is to create a fermentation "chamber"...this is simply a fridge or freezer of any size, fitted with a digital temperature controller that can be set at your desired fermentation temperature. Need help with this one? Give us a call and we can walk you through it or help to build it for you!
So there it is...if you're going to brew in the summer, do your best to control your fermentation temperature so you can keep on brewing awesome beer!