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Section 1 – Brewing with Malt Extract
Chapter 10 - What's Different for Brewing Lager Beer?
What makes lager beer different from ale beer, you ask?
Well, the main difference is temperature. Make that temperature and time. No, there’s three: temperature, time and yeast. Let’s start with yeast.
Yeast Differences
As discussed in Chapter 6 – Yeast, lager yeasts like lower fermentation temperatures. Lager yeast produce less fruity esters than ale yeasts and have an enzyme that can ferment a sugar called raffinose that ale yeast strains can’t. Raffinose is a trisaccharide of sucrose and galactose, but it doesn’t actually occur in beer wort, so don’t expect an increase in attenuation; the ability of lager yeast to ferment raffinose is purely academic. However, lager yeast typically ferment maltotriose better than ale strains, so you will get a couple points more attenuation from that.
Lager yeast also produce more sulfur compounds during primary fermentation than ale yeast. Many first time lager brewers are astonished by the rotten egg smell coming from their fermentors, sometimes letting it convince them that the batch is infected and causing them to dump it. Don’t do it! Fortunately, these compounds continue to vent during the conditioning (lagering) phase and the chemical precursors of other odious compounds are gradually eaten up by the yeast. A previously rank smelling beer that is properly lagered will be sulfur-free and delicious at bottling time. Speaking of Time...
Additional Time
The lower fermentation temperature decreases the rate at which the yeast work and lengthens both the primary and secondary fermentation times. The primary phase for ales is often 2-5 days, but 3-7 days is normal for a lager. As mentioned in the previous chapter, the primary and conditioning phases of fermentation happen concurrently, but the conditioning phase takes longer. This is especially true with lager yeasts. The defining character of a lager beer is a clean, malty taste without ale fruitiness. Obviously, those rotten egg odors don’t belong either. The time that it takes for these compounds to be processed by the yeast can be several weeks to a few months. It depends on the malts used, the yeast strain, and the temperature at which conditioning occurs.
Author’s Note (2025): My understanding of lager yeast and lagering time has changed a lot since this was written in 2006. In fact, this is one of the biggest differences between the 3rd and 4th editions. Lager yeast actually maturate better at warmer temperatures with a diacetyl rest (more on this later in the chapter) at 60-65F, (15-18C), so that all of the diacetyl and acetaldehyde reduction is complete before the beer is chilled for lagering. Warm maturation allows for the lagering period to be solely concerned with clarification, which will typically occur within 10 days at 33F/1C.
That being said, yeast can also be trained to maturate the beer during a long and cold lagering process as has historically been done but this requires more expertise by the brewer.
Lower Temperatures
Lager comes from the German word “lagern” which means to store. A lager beer is in cold storage while it ages in the conditioning phase. Temperature influences lagers in two ways: flavor and clarity. During primary fermentation, the cooler temperature (45-55°F) inhibits the formation of fruity esters by the yeast. The cooler temperatures result in a longer conditioning phase to finish residual sugars and metabolize other off-flavors and aromas like diacetyl and acetaldehyde. The other main effect of lagering at cold temperatures is brilliant beer clarity. The traditional near-freezing lagering temperatures cause almost all of the haze forming proteins and tannins to settle out. See Appendix F for more info. Unfortunately, this long time with the beer in contact with the yeast can potentially cause a problem. The problem is autolysis, i.e., yeast breakdown, which can produce off-flavors in the beer.
Author’s Note (2025): Autolysis is thankfully rare at the homebrewing scale. It can happen with old or repitched yeast, but it is more prevalent in large commercial breweries where there is a large hydrostatic pressure at the bottom of the very large conical fermenters.
When a yeast cell dies, it ruptures—releasing several off-flavors (umami, rubber, etc.) into the beer. When you have a large yeast mass on the bottom of the fermentor, you have a large potential for off-flavors due to autolysis. A lightly autolyzed beer will have a yeasty or brothy aroma or flavor. Smelling a jar of Vegemite is a good comparison. A moderately autolyzed beer will have a meaty aroma/flavor that is very similar to the smell of a bottle of B Vitamins. A heavily autolyzed beer will have a rubbery aroma/flavor and will be virtually undrinkable.
Luckily, the propensity of yeast to autolyze is decreased by a decrease in activity and a decrease in total yeast mass. What this means to a brewer is that racking to a secondary fermentor to get the beer off the dead yeast and lowering the temperature for the long cold storage allows the beer to condition without much risk of autolysis.
As a final note on this subject, I should state that by brewing with healthy yeast in a well-prepared wort, many experienced brewers, myself included, have been able to leave a beer in the primary fermentor for several months without any evidence of autolysis. In fact, I didn’t even rack the last Vienna lager I made, just let it lager in the primary for 4 weeks, and it turned out fine. Autolysis is not inevitable, but it is lurking.
Lager Yeast Fermentation
It is easier to brew a bad lager than it is to brew a bad ale because the expectations are higher for lagers. Brewers and beer drinkers are more forgiving about off-flavors in ale, calling it "complexity", but lagers should be “clean”. A good lager should have a clean malt character with minimal off-flavors due to esters, diacetyl, acetaldehyde, or fusels. Lager brewing is best described in a book of its own, and fortunately Greg Noonan has done so with the New Brewing Lager Beer from Brewers Publications. I strongly suggest you read that book if you want to get serious about lagers, but meanwhile I will try to get you off on the right foot.
Author’s Note (2025): There is also a newer lager book, Modern Lager Beer, by J. Hendler and J. Connolly from Brewers Publications, 2024. I really recommend reading this book for a comprehensive review of lager brewing practices.
In my opinion, the most important step for brewing good lagers is understanding how the three factors mentioned above combine to determine the fermentation performance. A lager yeast fermentation is less active due to the cooler temperatures, so all the fermentation processes occur more slowly. In other words, it will take more yeast to ferment a wort at a lower temperature in the same amount of time that it would take to ferment the same wort at a higher temperature.
In the past, it was common practice for homebrewers to cool their wort to room temperature, pitch the yeast, and place the fermentor in a cool cellar or refrigerator at the intended primary fermentation temperature of 45-55°F/7-13°C (depending on yeast strain). The fermentation would start right up with a short lagtime and the activity would slowly decrease over the next few days as the beer cooled.
This sequence is not ideal because it can take a couple days for the wort to get down to the proper fermentation temperature. Most of the fermentation byproducts are produced in the first couple days of fermentation as the yeast go through their exponential growth phase. The amount of byproducts produced is proportional to the level of yeast activity (i.e., vigor), which is proportional to temperature. So, the warmer the wort is in the first days of fermentation, the more total byproducts there are for the yeast to clean up during conditioning. And, as the wort cools down after all of this initial activity, the yeast are less efficacious at cleaning up the byproducts.
The best way to ensure a strong, healthy lager fermentation is to pitch more yeast than you would for an ale. You should use 150 billion cells for a 1.050 OG lager where you would have pitched 100 billion cells for a 1.050 ale. This is the equivalent of about 1⁄2 to 3⁄4 cup of yeast slurry. Recommended pitching rates for lager beers are given in Table 11. When you need to pitch a large starter, I recommend that you ferment that yeast starter at no more than 5°F (3°C) above the primary fermentation temperature. After the starter fermentation finishes (~2 days), I recommend chilling the starter in the refrigerator overnight to settle all the yeast.
On brewing day, when you are ready to pitch your yeast, take the starter out of the fridge and pour off most of the starter beer. Swirl up the remaining beer and yeast and pitch this to your wort while the yeast is still cold. Experience among homebrewers has shown that pitching yeast to a relatively warmer wort shortens the acclimation period of the yeast. Also, pitching only the slurry avoids some off-flavors from the starter beer.
Lager Brewing Particulars
Pitching Rate
The pitching rate can have a large effect on the character of the beer, and this is especially true with lagers. In the first few days of the fermentation cycle, when the yeast are rapidly reproducing, more diacetyl pre-cursor (acetohydroxy acids), acetaldehyde, and fusel alcohols are being produced than at any other time. Low pitching rates means more total cell growth, more amino acid synthesis, and therefore more byproducts. High pitching rates mean less total cell growth and less byproducts. The general rule is 1.5 billion per liter per degree Plato. Remember that 1°P = 4 gravity points.
Wort Nutrients
The other aspect to consider is yeast nutritional supplements, namely oxygen and amino acids. Either of these will encourage yeast growth. The oxygen can come from aeration with an aquarium pump and airstone, or from an oxygen tank. With the aquarium pump, you will never get above 8 ppm of dissolved O2, which is the average requirement for most yeast strains, and some strains like more, e.g., 12 ppm. If you use an oxygen tank, you can hit 40 ppm after a half hour, which is too much and can cause excessive cell growth and a corresponding increase in diacetyl and fusel alcohols. See Chapter 6 for more info on recommended oxygen levels.
Diacetyl
Diacetyl is not actually produced by the yeast. The vicinal diketones diacetyl and pentanedione are created chemically by oxidative decarboxylation, (i.e., removal of hydrogen and carbon dioxide) of the acetohydroxy acids. Warm temperatures and the presence of oxygen promote this reaction. The ability of the yeast to remove diacetyl is about ten times the creation rate, but as the wort temperature finally gets to the primary fermentation temperature, the yeast activity decreases and are slower to biochemically reduce it. The result is a buttery/butterscotch flavor in the lager, which is considered an off-flavor. Some amount of diacetyl is considered good in other styles such as dark ales and stouts, but is considered a flaw in most lager styles. To remove any diacetyl that may be present after primary fermentation, a diacetyl rest may be used. This rest at the end of primary fermentation consists of raising the temperature of the beer to 55–60°F (12-16°C) for 24–48 hours before cooling it down for the lagering period. This makes the yeast more active and allows them to eat up the diacetyl before they flocculate during chilling. If you are racking to a secondary fermenter, be careful to minimize oxygen contact during racking because this will generate still more diacetyl.
Acetaldehyde
Acetaldehyde production is often at odds to the other byproducts. It is produced early in the fermentation cycle as part of the ethanol production process and is reduced later. It is typically caused by rapid fermentation due to warm temperatures (>60°F) or by over-pitching and under-aeration. It is reduced by conditions that favor the maturation processes such as warmer lagering temperatures (40-45°F vs 30-35°F), keeping the beer on the yeast longer, and keeping the yeast suspended. In addition, a less-flocculant yeast strain will allow more time for acetaldehyde reduction. Acetaldehyde will also be reduced by the yeast during a diacetyl rest.Fusel Alcohols The fusel alcohols are not reduced by the yeast and will affect the final flavor of the beer. While a few fusel alcohols can be esterified, it is a minor path and not a viable means of fusel reduction. In other words, if the beer smells like solvent or rubbing alcohol, don’t count on six months of maturation to fix it. Fusel alcohol levels are increased by warmer temperatures, excessive aeration, excessive amino acids, and under-aeration and a lack of amino acids. To control fusel alcohols: • increase the pitching rate, • pitch when the wort is cool, • ferment at the lower temperatures in the suggested range, • don’t add sucrose or other refined sugars to the wort.
Esters
An ester is a compound formed by the yeast from an alcohol and a fatty acid in order to de-toxify their environment. Most esters in beer are produced by esterification of ethanol with Acetyl CoA and short-chain fatty acids. The enzyme Alcohol Acetyl Transferase (AAT) plays an important role in this process. Fusel alcohols can also esterify with fatty acids, but usually the concentrations of these esters are very low. Ester formation is encouraged by:• under-aeration• under-pitching• pitching warm• warm fermentation temperatures• high-gravity worts• worts with a significant proportion of refined sugar.
SummaryTo summarize, a bad lager beer could have some or all the following flaws: • a sweetish buttery aroma/flavor due to diacetyl• a green apple aroma/flavor due to acetaldehyde• sharp solvent-like aromas/flavors due to fusel alcohols• fruity aromas/flavors due to esters.The recommended way to produce a clean lager beer is to:• Cool the wort to primary fermentation temperature before pitching the yeast• Pitch a relatively high quantity of yeast to limit cell growth• Aerate sufficiently, but not excessively• Don’t chill/lager too soon, give the yeast time to finish the job.
Figure 68 - my drawing of lagering barrels
Table 11 – Recommended Lager Pitching Rates
Table 12 - Est. Cell Counts based on Initial Count and Starter Size
When to Begin Lagering
It takes experience for a brewer to know when primary fermentation is winding down and the beer is ready to be transferred. If you insist on brewing a lager for your very first beer, you are going to be flying blind. You can play it safe by waiting several weeks for the primary phase to completely finish (no more bubbling) and rack then, but you will have missed your opportunity for a diacetyl rest. As discussed in the previous chapter, you should rack to a secondary when the krausen has started to fall back in. The bubbling in the airlock will have slowed dramatically to 1 or 4 bubbles per minute, and a hydrometer reading should indicate that the beer is 3/4 of the way to the terminal gravity. Knowing when to rack takes experience, it’s as simple as that.
Author’s Note (2025): Yes, the above is true but it is needlessly mysterious. There is nothing mysterious about modern lager brewing. Use a diacetyl rest, raising the beer temperature by at least 5F/3C as the bubbling rate slows down as described previously. This may be day 3 or day 4 of fermentation. Raise the temperature by changing the setting on your temperature controller, or moving it to a warmer room, or putting a heating pad around it. Let the diacetyl rest proceed for at least 24 hours, if not 48. You will not be hurting your beer in any way by raising the fermentation temperature at this stage. My beers have literally rested for a week at the raised temperature, and they were exceptional.
(back to 3rd Edition text)I like to ferment and lager in glass carboys because the glass allows me to see the activity in the beer. During primary fermentation, there are clumps of yeast and trub rising and falling in the beer and it’s bubbling like crazy—it literally looks like there is someone stirring it with a stick. When you see that kind of activity slow down, and things start settling towards the bottom, you know the primary phase is over and it’s safe to rack.The lagering temperature and duration are affected by both the primary fermentation temperature and the yeast strain. Some general guidelines for lager fermentation times and temperatures are listed below:• Check the yeast package information for recommended fermentation temperature(s).• Suggested lagering times are 3-4 weeks at 45°F (7°C), 5-6 weeks at 40°F (4°C), or 7-8 weeks at 35°F (2°C).• Nothing is absolute. Brewing is as much an art as it is science.A common question is, “If the beer will condition faster at higher temperatures, why would anyone lager at the low temperature?” Two reasons: first, in the days before refrigeration when lager beers were developed, icehouses were the common storage method—it’s tradition. Second, the coldest lagering temperatures work better to precipitate extraneous proteins (like chill haze) and tannins to produce a smoother beer than the warmer lagering temperatures.
Author’s Note (2025): To generalize, there are two paths you can take with lagering times and temperatures. I recommend using a diacetyl rest and giving the beer a solid week of warm maturation time before you chill it to lager, and then your lagering time for clarification only needs to be about 2 weeks, regardless of style or strength. The other path is the traditional long and cold way and that really does require experience. You need to give the yeast lots of time for both primary and secondary fermentation because you are going to cool the beer slowly down to 5°C/41°F and then hold it there for a couple weeks before cooling further for lager at 1°C/34°F. When you do chill, do it slowly to avoid stressing the yeast. I recommend a maximum cooling rate of 3°C/5°F every 12 hours. I discuss yeast behavior, fermentation, and lagering much more thoroughly in the 4th edition of How To Brew (Brewers Publications, 2017).
Aagh!! It Froze!!!
By the way, what if your beer freezes during lagering?? Horrors!!Well, it happened to me. Let me tell you about my first lager...
‘Twas a few weeks before Christmas and all around the house, not an airlock was bubbling, in spite of myself. My Vienna was lagering in the refrigerator out there, with hopes that a truly fine beer, I soon could share.
The Airstat* was useless, 32°F couldn’t be set, so I turned the ‘fridge to Low, to see what I would get. On Monday it was 40°, On Tuesday lower yet, On Wednesday morning I tweaked it, seemed like a good bet.
Later that day when I walked out to the shed, my nose gave me pause, it filled me with dread. In through the door I hurried and dashed, when I tripped on the stoop and fell with a crash. Everything looked ordinary, well what do you know, but just in case, I opened the ‘fridge slow.When what to my wondering eyes should appear, My carboy was FROZEN, I had made Ice beer! My first thought was tragic, I was worried a bit, I sat there and pondered, then muttered, “Aw Sh##!”
More rapid than eagles, my curses they came, and I gestured and shouted and called the fridge bad names. “You Bastard! How could you! You are surely to blame! You’re worthless, You’re scrap metal, not worth the electric bills I’m paying! To the end of the driveway, with one little call, They will haul you away, haul away, haul away all!”
Unlike dry leaves that before the hurricane fly, when brewers meet adversity, they’ll give it another try. So back to the house, wondering just what to do, five gallons of frozen beer, a frozen airlock too. And then in a twinkling, I felt like a goof, the carboy wasn’t broken, the beer would probably pull through.
I returned to the shed, after hurrying ‘round, gathering cleaning supplies, towels, whatever could be found. I’d changed my clothes, having come home from work, I knew if I stained them, my wife would go berserk. I was loaded with paper towels, I knew just what to do, I had iodophor solution and a heating pad too.
The carboy, how it twinkled! I knew to be wary, the bottom wasn’t frozen but the ice on top was scary! That darn refridge, it had laid me low, trying to kill my beer under a layer of snow. I cleaned off the top and washed off the sides, picked up a block of ice and threw it outside. I couldn’t find the airlock, it was under the shelf, and I laughed when I saw it, in spite of myself.
The work of a half hour out there in the shed, soon gave me to know, I had nothing to dread. The heating pad was working, the ice fell back in, I re-sanitized the airlock, I knew where it had been. Not an Eisbock, but a Vienna I chose, it was the end of the crisis of the lager that froze.
I sprang to my feet, to my wife gave a whistle, and we went off to bed under the down comforter to wrestle. But the ‘fridge heard me exclaim as I walked out of sight, “Try that again, you bastard, and you’ll be recycled all right!”
* The now discontinued Hunter Airstat™ was a window-unit air conditioner temperature controller that we used to regulate the refrigerator more precisely than the normal controls. Nowadays, we actually have temperature controllers specifically designed and built for home brewing.
Should I Add More Yeast?
When your lager freezes, chances are the yeast has been impaired. If you are towards the beginning of the lagering cycle, then there may not be enough yeast activity after it thaws to properly complete the attenuation and condition the beer. You should probably add new yeast. If you are at the end of the lagering cycle, and were planning on priming and bottle conditioning it, then you should probably add more yeast also. If you are planning on kegging it and force carbonating (like I was), then you don’t have to worry about it. I say “probably” because some yeast will survive. Even if the beer freezes completely for a short time, typically 20% of cells will remain active. The questions are: 20% of how many, and just how active? Therefore, you should probably add new yeast.
The yeast you add to the fermentor should be of the same strain as the original yeast. If you are using yeast from a ready-to-pitch package, then that quantity is probably sufficient and you can pour it right in and swirl it around to mix it evenly. Because you are not trying to conduct a primary fermentation and are not concerned about a fast start, you do not need to build up the count any further, nor do you need to acclimate it to the lagering temperature first. The yeast will acclimate over several days and finish the fermentation cycle. The small amount of primary fermentation byproducts that you add to the beer by pitching at full krausen will not affect the flavor significantly.
Maintaining Lager Temperature?
Temperature controllers, such as from Johnson Controls, Ranco, and Ink Bird, are very handy for maintaining a constant brewing temperature in a spare refrigerator. Controllers work by plugging into the wall outlet and then plugging the fridge into it. A temperature probe is run inside the fridge and it governs the on/off cycling of the compressor to maintain a narrow temperature range. Here in Southern California, I use it to maintain 65°F in the summertime for brewing ales. Check your local homebrew supply shop or some of the larger mail order suppliers for one of the newer controllers. Some controllers will also operate a separate heating circuit (usually in conjunction with a heat lamp) for cold weather brewing conditions.
In my case, my frozen Vienna lagered for 6 weeks at 34°F. I placed blocks of ice next to the carboy instead of relying on the refrigerator for temperature control. In fact, insulated ice boxes are a good way to control temperature for lagering. The blocks of ice will last about 3-4 days. Because of the alcohol present, the beer actually freezes at several degrees below normal. Depending on the time of year and your ambient temperature, an insulated box (like a large picnic cooler) is a very convenient way to lager. My Cold But Not Baroque Vienna lager went on to take first place in two separate contests in the Vienna/Oktoberfest category.
Bottling
See the next chapter, Priming and Bottling, for information on how the bottling and carbonating of lager beers can differ from ale beers.
Brewing American Adjunct Lager
Author's Note, 2025: This is from 2006. There are better, more detailed recipes available elsewhere on the internet than this particular one.
A lot of people want to know how to brew their favorite American light lager beer, like Bud, Miller, or Coors. First thing I will tell you is that it is difficult to do. Why? Because these beers are brewed using all-grain methods that incorporate rice or corn (maize) as about 30% of the fermentables. The rice or corn must be cooked to fully solubilize the starch and then added to the mash so that the enzymes can convert the starches to fermentable sugars. See Chapters 12 and 14 for more info.
Second, there is no room in the light body of these beers for any off-flavors to hide. Your sanitation, yeast handling, and fermentation control must be rigorous for this type of beer to turn out right. The professional brewers at Bud, Miller, and Coors are very good at what they do—turning out a light beer, decade after decade, that tastes exactly the same.
You can brew either rice or corn-type lagers. Rice extract is available in both syrup and powder form, and will produce a beer similar to Heineken or Budweiser. Refined corn syrups and corn sugar have had most of their corn character stripped away but will still produce a beer similar to Miller or Coors. To brew these American lager styles most accurately, you need to find syrup that is high in maltose. They can be hard to find, so if you buy corn syrup at the grocery store, check the ingredients to avoid additives like vanilla. Also, look at the ratio of sugars to total carbohydrates on the nutrition label to get an idea of the fermentability. The grocery store corn syrups are typically high in dextrins for body.
To brew a corn-type lager, substitute corn syrup for the rice syrup below. If you want to brew a Classic American Pilsner (CAP), with a richer corn character, refer to the recipe in Chapter 20 “Your Father’s Mustache,” for appropriate OG and IBU levels. The cereal mash procedure using flaked corn or corn grits described in the “YFM” recipe will produce more corn character than extract methods using corn syrup.For more lager recipes, see Chapter 20.
American Adjunct Lager Style GuidelinesOG: 1.035-50, FG: 0.098-1.012, IBUs: 8-22, Color: 2-8 SRM
Commercial Example:American Lager Budweiser
Typical American Adjunct Lager BeerMalts Gravity Pts.3.5 lbs. of pale DME 491.5 lbs. of dry rice solids (powder) 21BG for 3 Gallons 1.049OG for 5 Gallons 1.042Hops Boil Time IBUs1 oz of Tettnanger (5%) 60 171⁄2 oz of Tettnanger (5%) 10 3Total IBUs 20 American Lager Yeast or Saflager W-34/70 Fermentation Schedule 2 weeks at 50°F in primary fermenter rack and lager at 40°F for 4 weeks. Prime and store bottles at room temperature until carbonated.
Typical American Adjunct Lager BeerMalts Gravity Pts.3.5 lbs. of pale DME 491.5 lbs. of dry rice solids (powder) 21BG for 3 Gallons 1.049OG for 5 Gallons 1.042Hops Boil Time IBUs1 oz of Tettnanger (5%) 60 171⁄2 oz of Tettnanger (5%) 10 3Total IBUs 20 American Lager Yeast or Saflager W-34/70 Fermentation Schedule 2 weeks at 50°F in primary fermenter rack and lager at 40°F for 4 weeks. Prime and store bottles at room temperature until carbonated.