The Warm Lager Method
by Dr. Mickie Willis (Brewing Techniques)
How to Brew Lager Beer at Room Temperature
With the help of insights gained from acoustical theory, one brewer discovered a simple method of brewing crisp, clean lagers at room temperature.
I suspect most home brewers brew more ales than lagers because of the limitations in their household work spaces rather than because of their drinking preferences. Although the popularity of home brewing has increased interest in a greater variety of beer styles, particularly ales, over the past 20 years, beer sales suggest that most Americans prefer lagers. How many more of us would take up lager brewing if it were possible to brew good, clean lagers in our kitchens, without any means of refrigerating the fermenting vessels?
Despite the conventional wisdom that fermentation must be carried out under refrigeration, it is reasonably easy to create crisp, clean lagers, free of the esters, diacetyl, and fusel alcohols that so often mar our efforts to duplicate some of the world’s best beers. The methods presented here are the result of some simple innovations in my home brewery, inspired by the basics of acoustic theory as applied to speaker construction (see box).
Want to brew your own lager at home? Choose from one of our recipe kits!
Challenging a Cool Tradition
Much of the difference between ales and lagers is caused by the strain of yeast, of course, but even the best lager yeasts will produce ale-like flavors if allowed to ferment too warm. The traditional strategy for containing this activity (probably discovered accidentally and empirically reinforced) has been to conduct fermentation at cool temperatures (40–55 °F). Good results can be obtained, however, even if temperature is kept low only during kräusen and then allowed to rise to room temperature levels later in the fermentation! While it may be difficult or impossible for home brewers to keep fermentors cool during the entire fermentation process, especially during the summer months, it is easier to keep them cool at the beginning of fermentation — the most important time to keep temperature in check!
Although large batches are typically more difficult for home lager brewers because they are more difficult to keep cool, in this case the larger the batch, the better; thermal inertia slows the gradual rise to to ambient temperature. The rise to room temperature can be further slowed by using an insulated fermentor such as a doubled-walled plastic water cooler. A 10- or 15-gal batch in a well-insulated cooler will take several days to reach ambient temperature. By this time, the most critical time of the creation of unwanted fermentation by-products will have passed. In fact, elevation of temperature late in fermentation is a tactic often used by commercial breweries (most notably in Germany) to help boost the activity of yeast strains that do not easily reduce diacetyl levels produced during kräusen. In this way, brewers effectively damp the most active phase of the process — the fermentation “resonance” (see box) — by deliberately making conditions less conducive to yeast activity at the time when it is most energetic.
| Borrowing Lessons from Acoustical Theory |
| What does brewing have to do with acoustical theory? After all, acoustics involves the mechanical behavior of sound, and brewing involves biological processes. The two share one interesting trait: Both work with uneven energy outputs that must be contained for one reason or another, and both require the careful management of natural tendencies. Audio engineers, for example, need to design speaker systems that have the most linear audio output possible over the entire range of human hearing. An acoustical driver (speaker), for example, and the air captive inside its enclosure (both the box in which the speaker is enclosed and the room or auditorium into which it plays) vibrate more efficiently at some frequencies than at others. This varied efficiency causes electrical energy input to result in more acoustic output at some frequencies than at others. Uneven response is characteristic of poor speaker systems and is the root of the phrase boom box, now applied to large portable stereos. Audio engineers and acousticians use the term Q to describe the degree of magnification at resonance of a speaker, speaker system, or other vibrating body. The higher the magnification, the higher the value of Q. We’ve all experienced the effect of high-Q resonance while singing in reverberant environments such as showers, which magnify a narrow range of frequencies (often 70–200 Hz) and makes even the weakest male voice seem rich and powerful. It is the challenge of high-fi speaker designers to design enclosures that damp this magnification at resonance — the speaker system Q — so that the response is as uniform as possible. Lager brewers too must damp a resonance of sorts to achieve smooth, clean flavor. For us, the high-Q resonance of fermentation is the period of most intense yeast activity, which occurs for the first several days after the lag period. We call this the respiratory, or kräusen, phase, and recognize it as a normal part of brewing. But most of the by-products of yeast metabolism that characterize ales — and that are undesirable in lagers — are formed during this time. Just as audio engineers damp excessive audio output from speakers by designing a box that inhibits the natural resonance of the speaker, so too can brewers effectively damp the most active phase of the fermentation process by deliberately manipulating conditions that are less conducive to yeast activity at the time when it is most energetic. The analogy goes even further. Take, for example, the case of an unenclosed speaker that has a very high Q at a resonance of 100 Hz. A designer may calculate the dimensions of a box that contains a volume of air that resonates at a different frequency (perhaps 50–75 Hz), which would be out of phase with the speaker. Rather than reinforce the uneven response of the speaker, the box tames the unevenness. The two bodies, with their resonances at frequencies that inhibit each other, will couple to produce a unified sound output that is smoother over a broader range of frequencies than either alone. In brewing, when we lower the temperature of the wort at the beginning of the fermentation and allow it to rise slowly, later in the process, the temperature curve is “out of phase” with the natural tendency of the yeast body. In the early stages of fermentation, when the yeast is naturally most active, we can inhibit it with low temperatures. Later on, when the yeast naturally tends to become less active, allowing the temperature to rise will increase its activity. Thus, the two factors combine to yield a smoother, more uniform rate of activity than would be the case without “out-of-phase” temperature manipulation. This temperature containment, in effect, becomes the “thermal box” that couples to the yeast activity. The methods used by audio engineers to damp acoustical resonances and rid speakers systems of excessive behaviors provides an interesting lesson for brewers. By diminishing the natural unevenness of fermentation, brewers can produce excellent lagers at room temperature. |
The strategy is to begin fermentation at a very high pitching rate, but at very cold Temperatures — around 40 °F. This flies in the face of conventional wisdom among home brewers, which recommends that yeast be pitched at a temperature somewhat warmer than its standard fermentation temperature and then gradually lowered to a cooler range. With proper pitching rates, however, fermentation will begin within 8–12 hours even at temperatures as cold as 40 °F.
|
| Have any feedback on this article? We want to hear from you! Click here, to contact us with any feedback. Did you enjoy reading this article? Interested in writing one? Click here, to learn More! About becoming a contributor. Or simply email us at articles@morebeer.com |
Procedures for Lagering at Room Temperature
My method for room temperature lager brewing begins with boiling a concentrated wort (whether extract or all-grain), chilling it with ice to near freezing for the best possible cold break, and racking off the trub. This procedure leaves only about 3–4 gal of clear, high-gravity wort (in a 6-gal kettle), to which I add water that has been chilled in my refrigerator. If the water in your area is not reliably free of bacteria, distilled water is cheap enough to buy in convenient 2-gal jugs, or you can preboil water and refrigerate before brewing day. I then pitch the yeast, usually at around 40 °F (4–5 °C). I then allow the fermentation to proceed undisturbed. Of course, the cooler the surroundings, the longer the temperature inside will remain cool, even in an insulated vessel, and the better the results.
| Room-Temperature Lagering — A Quick Overview |
| Any good beer requires good brewing methods, such as proper pH in the brew kettle, adequate cooled-wort aeration, and the use of high-quality ingredients. To create a crisp, clean, clear lager at room temperatures requires some additional tricks and considerations.
|