Can Conditioning

What is it, and why did we decide on this method for Strong Dark Mild?

With the newest Union-fermented beer, a Strong Dark Mild brewed with our friend Garrett Oliver, we decided to make this our first-ever can-conditioned beer.  All of the non-draught, Union-fermented beers have been conditioned in bottle so far; we have a real love of the effect bottle conditioning has on the beer and wanted this replicated in a can for this project. 

For most of our brewery-conditioned beers (think bottle, keg and can rather than cask) we carbonate the beer to a set level by forcing CO2 into the beer prior to packaging.  This is an efficient, simple processing step and is easily measured in-house on one of our CO2 meters.  Much of the CO2 in the beer comes from the primary fermentation, as we capture this in the beer by sealing the tank towards the end of the process.  The forced carbonation then tops up or trims the CO2 level to the desired amount of effervescence (fizziness!). 

But what is can-conditioning?  In the simplest terms, it is a method of carbonating the beer in the can after we’ve packaged it.  Just before we can the beer, we add a set amount of sugar and some yeast to the tank and rouse it through the beer gently.  After canning and while the beer is stored somewhere warm, the yeast in the cans gets to work and turns the sugar into carbon dioxide (and a bit more alcohol).  The beer referments and carbonation is produced.  This natural process takes approximately 1-2 weeks to complete, which means we don’t put the beer on sale for up to 2 weeks after we’ve packaged it.

It’s important to make sure you add exactly the right amount of sugar (dextrose to the beer to make sure it’s not too fizzy, or not fizzy enough.  We’ve been bottle conditioning some of our beers for a long time now so are well accustomed to getting this bit correct.  The choice of yeast to do the job is also important.  It’s often unwise to use the yeast that was involved in the primary fermentation of the beer as it can be tired and perhaps not as healthy as a fresh dose.  For our bottle (and now can) conditioning, we use what is effectively a champagne yeast, which excels at refermenting beers and forms a tight mat at the bottom of the vessel after refermentation.   

So why do we bother?  We believe that conditioning the beer in can (or bottle) can give more complex flavours, removes oxygen from the package (which helps with shelf life) and also gives a finer, softer carbonation with greater mouthfeel.  Not all of our beers suit this method, but we felt this strong dark mild would be perfect for it.  This is a luxurious beer, so keep the can upright, chill to below 12C, open carefully and pour gently into your favourite beer glass.  There may be a small sediment in the bottom of the can, but this will be mostly left behind if you follow these steps!

Written by Dominic Driscoll