Brew Tech Talk: Lagering

Most beer brewed all over the world is lager beer. What does that mean? Lager. In the end, it means beer that has been stored in cold lockers for drinking later--dating from a time in the past when brewing could not be done in summer because the wild yeast were...well too wild.

By selection over time, a new variant of yeast developed-- bottom-fermenting yeast. Instead of rising to the top to be collected for the next brew, this yeast fell to the bottom out of harms way. It could work at colder temperatures too. Some yeast always stays in suspension, however, and therein lies our tale.

That beer stored away, or lagered, for a period of time was found to taste smoother and more refined. Drinkers began to seek out these beers that were brewed the new way. New in this case refers to a long time ago. What happens to lagered beer?

Backing up, let's consider primary fermentation. Here the yeast gobbles up sugars as fast as it can and injects lots of flavors into the green beer. Trub, parts of proteins, hops, etc., drop out. At the end, and that's how we tell it's the end, most of the yeast drops out too. Now we go to secondary fermentation by racking the beer to another vessel, leaving the trub and settled yeast behind. This may be the start of lagering or it may be just another way to settle the beer before sending to the cellar. One traditional way is to wait until there is 1 percent fermentable sugar left and then bung up the secondary vessel (or transfer it to a closed vessel). Another is to wait until it's done and then transfer it to a closed vessel with a little fermenting beer from a primary.

However we do it, we now have a stable environment with a small amount of no-longer-reproducing yeast slowly working on the fermentation products of the exuberant primary yeast. These few remaining cells will keep the beer safe from bacteria and put fine bubbles in the brew. Less is more in this case.

OK, now we really are in a closed tank for lagering. What are we looking for? Let's ask the Wizard. Read the whole thing.

After lagering, most lager brewers want a reduction in diacetyl (butter flavor), acetaldehyde (apple flavor), and sulfur-based aromas (rotten egg); full carbonation; and an improvement in clarity. Most brewers consider diacetyl reduction to be the key goal of lagering.

Well, OK. How long do you lager? Depends on the beer:

Some beers do benefit from longer aging periods, especially stronger beers. Doppelbocks typically lager for well over two months. Strong beers mellow over time — obvious flavors that are present when the beer is young slowly meld into a complex palate of intriguing, hard-to-describe flavors.

Yeah, hard-to-describe alright. Very few analytical tests can be used to back up the desire to lager a beer, especially for a long time. Human taste can far exceed any instrument that technology has come up with so far.


Now we, the consumers, know that lagered beer tastes better. Naturally, commercial brewers want to get that taste faster and cheaper. Here's more from the Wizard, but not all of these techniques are practical or even desirable:

Time saver number one: In recent years some lager brewers have begun warming the beer between fermentation and lagering, usually from about 50° to 70° F. This process accelerates the conversion of alpha-acetolactate (a compound normally secreted by yeast) to diacetyl and also accelerates the uptake of diacetyl by yeast. Diacetyl reduction is one of the key objectives of lagering, so this technique is used by many brewers, especially brewers in Germany, where this idea originated.

This technique does not make the beer fruity, because fermentation is complete and the yeast have produced all of their fermentation aromas. Many commercial brewers can’t easily employ this method because their cellars are not designed to warm beer; they are designed to keep it cold. Homebrewers, on the other hand, can easily change beer temperature by simply moving it across the house!

To try this method ferment the lager at 50° F, rack the beer to the secondary, and move it to a room temperature area for two to three days. Then chill the beer to 32° to 40° F for lagering. Two weeks of lagering should be long enough for lighter lagers such as pils and helles.
Time saver number two: Yeast contact is a good thing. The key to flavor maturation is yeast. Increasing the contact between yeast and the compounds they are modifying can reduce lagering times. Some people think beechwood chips are just for marketing, but in reality they are a traditional method of improving lager times. Oddly enough, they are such a pain to handle that very few breweries in the world continue this tradition (chip trivia: most American lager brewers in the 1800s used "chip tanks" for lagering).

Another way to increase yeast contact with beer is to use non-flocculent yeast. Although this makes clarification difficult, it does accelerate the aging process. With modern centrifuge technology the clarification issue is less important. After the beer is properly aged, the yeast is removed using centrifugation. This method cannot be practiced at home because a pilot centrifuge costs about $70,000. Sorry!

Time saver number three: The most modern lagering technique combines warming beer to convert alpha-acetolactate to diacetyl and a high yeast-to-beer concentration. First comes centrifuge, then pasteurization. The beer is recirculated through a column filled with yeast for rapid "aging" then filtered. The result is continuous lagering. It reduces lagering time from weeks to about a quarter of a day!

We have a spring megabrew coming up and one idea is to make a Martzen and lager it until our Octoberfest party. How's that for tradition? But what if you are not set up for cold fermentation or lagering? Here's some advice from Brewing Techniques. One item:

Ice is nice: During the 1800s the grandfather of the modern refrigerator, the icebox, was used in industry and home to maintain cool temperatures. The icebox is a very simple device: you simply put a large block of ice in the top compartment and it cools the bottom compartment. It offers no real control of the temperature, however, and as the ice melts, it cools less, which means you have to replenish the ice regularly. Back then, the ice used to stock an icebox came from Mother Nature. During the cold winter months, ice was cut from lakes and stockpiled in caves or sawdust-filled ice houses. Large breweries of that period used this same stockpiling technique to create lagering caves. Similar techniques can be applied, on a smaller scale, at home.

Modern insulating materials can be used to make a brewer's icebox. The carbon-insulated icebox that your grandparents had would be about the right size for a 5-7 gal carboy. Unfortunately, the only place you're likely to find one is in the local antique store, and usually antique means expensive. A more affordable option would be to build an icebox that combines modern insulation with old designs. Plans for these units can often be found in publications like Mother Earth News and Homestead.

I've used a water bath and soda bottles partially filled with water frozen in the refer. Use two sets and put one set in the bath while the other is freezing. I used to change them before and after work.

OK, the bath trick works good for fermentation but is too much of a drag for long time lagering. So you'll need one of the other techniques in the article.

One trick that always works: buy a new refrigerator for the kitchen before the old one breaks! Old one goes to the garage with a temperature controller on it. Have your brewing partner do it too and you get a fermentation and a lagering box--avoid the tedious :) changing of the controller.