Lagering and cold conditioning

Lagering logistics

Lagers are wonderful things. Crisp, clean, brilliantly clear and refreshing.

They are welcome on any hot afternoon and particularly good after any sort of sweaty work.

As well as a modern marketing term, there is a technical classification of a lager. True lagers use a special yeast strain, are fermented cold and fermented for longer.

If you can put lagering into action with your expanded kit beer techniques, the brewing gods will reward you.

How do I brew a lager then?

Use a lager yeast

All brewing yeasts are either classified as ales or lagers.

Lagers are beers brewed with a lager yeast (Saccharomyces uvarum to be precise).

The difference between ale and lager yeasts is that:

  • Lagers are fermented at cooler temperatures and have less fruity esters.

  • The yeast works on the bottom of the fermenter, not the top.

  • Lagers take longer to ferment and need to be cooled for an extended period after primary fermentation.

Often ‘lager’ homebrew kits will come with a clean tasting ale yeast. The tell-tale sign is a recommended fermentation temperature above 64°F (18°C).

Swap this out for a premium lager yeast and you’ll get a much better result.

Lagering fermentation technique

The word lager, as you may have found out through your homebrewing research, means to store.

The brewing reference historically traces back middle-age Germany when brewers would store their beer in freezing caves over winter.

Come spring, their patience would be rewarded with crisp and refreshing beer.

For the homebrewer, this means using a lager yeast, fermenting at a cooler temperature and storing cold for a while. Over this time any harsh compounds produced during fermentation are mellowed.

The most practical way to lager is to set up a fermentation fridge with an external thermostat.

If you are brewing in winter however, lagering can be as simple as moving your fermenter to the freezing cold garage.

What else should I know about lagering?

Pitch more yeast

Because they work slowly at lower temperatures, lagers need double the yeast count at pitching.

Tell them about the smell...

Well… they can smell like rotten eggs. Yep, lager fermentations can create sulfur compounds that smell like rotten eggs. Assure your loved ones it is a temporary arrangement.

When I first brewed a lager I thought it was infected!

Luckily I persisted through to bottling and the end beer was fantastic.

Rest assured that these compounds will dissolve through lagering and the end beer will be great.

Cool, warm, cold

Lager fermentation has a distinct cycle. The beer is fermented cool, warmed slightly for the last couple of days of primary fermentation and then chilled for an extended period.

The fermentation schedule of lagers is as follows:

  1. The primary fermentation runs at a cooler temperature. It varies with yeast strain, but is around 48 to 59°F (9-15°C). It will take from eight to ten days for primary fermentation to finish.

  2. At the end of the primary fermentation, it helps to raise the temperature to around 64°F (18°C) for two days. This will create more fermentation activity, which will consume a butterscotch-ish off flavor produced during primary fermentation. This compound is diacetyl, hence the step is called the diacetyl rest.

  3. Following the diacetyl rest, the wort is chilled to between 35 and 39°F (2-4°C) for two weeks. If you are brewing the perfect lager or a stronger beer you can chill for up to six weeks, but may need to add a small amount of fresh yeast at bottling time.

Cold conditioning ales

Cold conditioning an ale is basically a simplified version of lagering. It is used to quickly smooth out ales by chilling the fermented wort to 39-50°F (4-10°C) for a week or two.

It speeds things up

Given enough time, proteins, tannins and yeast will fall from suspension by themselves and smooth out your beer.

We might want to speed this up for a few reasons: Impatience. A party coming up. An empty beer fridge.

Whatever the reason, cold conditioning ales will quickly improve their taste and appearance.

The beer is also drunk fresh, so any hoppy or roasty notes are still there in all their glory.

Cold conditioning is particularly effective when combined with finings and racking to a secondary fermenter.

When and how to cold condition your ale

The trick to cold conditioning is to wait until the wort has fermented completely and the yeast has cleaned up any off flavors.

After fermentation, the yeast continues to consume fermentation by-products which would otherwise appear as flaws in your beer.

Hints of green apple, solvent or butter are a sign that your yeast was stopped prematurely through racking, bottling or crash cooling.

Ideally you would leave your wort at fermentation temperature for a week after fermentation has finished.

The yeast will clean up the wort during this time. Then you would crash cool and possibly rack with finings.

One to two weeks total cold conditioning time will make a huge difference to your beer.

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