How To Lager A Beer In 5 Steps
Step 1: Make a Starter
A starter consists of a little dry malt extract boiled with water and cooled in a lab flask or a small fermenter. It is essentially a mini-beer used to wake up the yeast and get them populated and healthy enough ferment a much larger batch of beer. This is best made a day or two before you ferment your lager.
Starters are mandatory for lagers. Since lagers are fermented at lower temperatures, yeast do not grow as fast as they do in ales, so starting out with a larger number of yeast is very important from a yeast health perspective. If you don’t pitch enough yeast, the ferment could go exceptionally slow, giving the chance for competing microbes to grow instead, ruining your beer. Pitching too much yeast could also be problematic since the yeast specific flavors in beer are created during their growth phase. If you do not allow the yeast to grow, you will not get these flavors!
Step 2: Boil
We kept this step short because you can use just about any beer recipe in existence and make a lager from it, just use a lager yeast!Time to brew! Throw all your ingredients into a pot and boil according to your recipe. You can stick to traditional lager styles such as maibocks, marzens, pilsners, and the like, or you can get crafty. Why not try an India Pale Lager? Or lager a stout? No reason at all! Any beer style can be lagered to tremendous results.
Step 3: Primary Fermentation; Pitch, and Keep it Cold!
Days 1 – 20: Chill your starter and your wort to the same temperature and pitch the yeast. Lagers must be fermented cold. This usually means a temperature range between 48º F and 55º F depending on the strain (found on your yeast producer’s website). Once they are , pitch the whole starter into your wort and seal your fermenter.
If commercial beer had a secret sauce that separates it from most of the world’s home brewed beer, this would be it. According to Dr. Chris White and Jamil Zainasheff, authors of Yeast: The Practical Guide to Beer Fermentation, “One of the greatest things a brewer can do to improve his beer is manage the fermentation temperature. This is far more important than using fancy fermentors or even all-grain brewing.” This sentiment is shared by professional brewers the world over. The reason is yeast produce a lot of byproducts during the fermentation process. These byproducts are small enough in number to be imperceptible to the human pallet when fermented at the right temperature. However when the fermentation temperature increases beyond the recommended level, the concentration of these byproducts increase well into the range of human perception. The result can be hot alcohol taste, green apples, butterscotch, and ester tastes like bananas and chewing gum, among many others. These are often viewed as classic homebrew flaws. So to make your homebrew taste less like homebrew and more like commercial beer, you must control the temperature of your ferment!
There are a number of ways to keep your fermenting beer at a consistent temperature. If you have an extra refrigerator in your house, put a temperature controller on it and get a thermowell for your fermenter. If you don’t have room for another refrigerator, BrewJacket’s Immersion chiller allows you to set a precise temperature for your ferment and it will maintain that temperature for the duration of your fermentation. It gets as low as 35 degrees below ambient, so you can not only brew precise ales, but lager anywhere you can fit a fermenter, such as a closet, or in the corner of your living room.
Step 4: Diacetly rest: Increase temperature to 65º F.
Days 20 – 23: By this point, your wort will have fermented into a beer! Lager yeasts take around 3 weeks to fully ferment the sugars into alcohol. During this process, they also create a compound called Diacetyl which has a pronounced butterscotch candy flavor. Diacetyl is produced by all yeast during first few days of fermentation, and is cleaned up by the same yeast after primary fermentation is complete. If left alone, the cleaning process will take upwards of 3 weeks. To speed this up, increase the temperature to the mid 60s and it will only take 3 days (warmer temps = faster yeast). It is safe to do this now because fermentation is complete all the flavor compounds you were after have been created already, so you aren’t at risk for any bad fermentation flavors sneaking in. It is a good idea to taste your lager every day using a thief until you can no longer detect any butterscotch. Once the butterscotch is gone, you’re ready to lager condition.
Step 5: True Lagering
Days 24 – 50: It’s lager time! Slowly lower the temperature from the 60s of your diacetyl rest to the low 40s or upper 30s and hold it there for a few more weeks. Be sure to lower the temperature slowly! By lowering the temp 1º to 2º per day, the yeast are slowly eased into the lager. This keeps them healthy for the next phase of fermentation. If you lower the temperature too quickly, they will be shocked into releasing a large amount of esters into the beer, potentially altering the flavor profile. The lagering process will assist in flocculation, allowing the solids to fall out of suspension and settle on the bottom of your vessel, producing an exceptionally clean final product.
Once complete, it is time to keg or bottle. Remember to sanitize your serving vessel before transferring. While fermentation temperature control is the separating factor between commercial and home brewed beer, forgetting basic sanitation will result in undrinkable and/or toxic beer. Keg or bottle your beer, and enjoy!
To learn more about yeast (believe me, there is A LOT to learn), I highly recommend picking up a copy of the book, Yeast: The Practical Guide to Beer Fermentation by Dr. Chris White and Jamil Zainasheff. Dr. Chris White is owner of the perennial yeast company White Labs, and Jamil Zainasheff has a fantastic show on the Brewing Network called The Jamil Show.