Brewing Lambic at Home


By Jim Liddil and Martin Lodahl (Brewing Techniques)


A Lambic Beer


Practical Strategies for Brewing Lambic at Home

Part I —Wort Preparation

Lambic represents an irresistible challenge to many beer aficionados’ most deeply ingrained beliefs about brewing. With the advent of commercially available wild yeast and bacteria cultures, home and professional brewers can now emulate the style away from its Belgian home.



In recent years, interest in Belgian lambic has grown to an extent few predicted. Even such relatively mainstream publications as Scientific American have carried articles on lambic, and a 1995 BrewingTechniques article on the style won a gold medal for beer journalism. The fact that true lambic can be made in only one area of the world gives it an air of mystery, but this limitation has unfortunately also contributed to the style’s near-extinction. Not only is its production area limited, but changing economic markets and shifting consumer preferences in its home region are bringing changes to the techniques and markets of some of Belgium’s traditional breweries.

With the commercial availability of “wild” yeast and selected bacteria cultures, however, it is now possible to brew lambic-style* beers anywhere in the world. This article is the first of three installments on brewing “authentic” lambic-style beers at home. This first part provides an overview of the beer and traditional lambic brewing methods and outlines various methods for preparing lambic-style wort for fermentation. Part II will focus on the mysteries of lambic-style fermentation, and Part III will cover conditioning, blending, packaging, and other miscellany.

*I refrain from using the word “lambic” to describe any beer made outside Belgium. True lambic is only made in a small area outside Brussels (though one American commercial brewer might have you thinking otherwise). I prefer to use the term “lambic-style” to describe similar beers made by home brewers. On the internet discussion group Lambic Digest, you can see the term “plambic” used, in reference to pseudo-lambics. The point is that real, true lambic can be made only in Belgium, the only place in which the unique wild yeasts that ferment lambic wort can be found in just the right balance.


The Anachronisms of Traditional Lambic

Lambic is defined by Belgian law and further protected by a European Union ordinance established in 1992 and by an appellation contrôlée from the European Beer Consumers Union. Belgian law defines lambic as spontaneously fermented ales made up of a grist of at least 30% unmalted wheat. Many additional idiosyncrasies combine to the make the style what it is.

Incompletely converted mash: Turbid mashing is the most traditional of lambic brewing techniques. It is similar to decoction, except that it involves removing and boiling liquid (rather than grain) portions of the mash. Unlike more mainstream mash methods, turbid mashing results in large amounts of unconverted starch in the finished wort.

Oxidized hops: Whereas most brewers want only the freshest of hops, lambic brewers rely instead on hops that have been stored in the open for 2–3 years until thoroughly oxidized and leached of their bittering properties. Old hops retain properties that allow lambic brewers to tame some of the beer’s “wildness” by controlling certain bacteria.

Intentionally “infected”: Lambic worts are not pitched with a pure strain of yeast, but are instead allowed to cool overnight in open cool-ships — large, shallow basins that maximize surface area for heat transfer and exposure to the air (pictured below). During the night the wort is inoculated with wild yeasts and bacteria that waft in through open windows. Lambic breweries typically only operate from about October to May due to lambic’s dependence on naturally occurring microbes, which can get out of hand during the summer months.

No stainless steel: The inoculated wort is fermented not in stainless steel vessels, but in old, unsanitized oak casks (pictured below). Some American home brewers intentionally infect their own casks to help authenticate their lambic-style ales.

Generously aged: Freshness dating will never be an issue in lambic circles. Lambic production is slow; it involves a period of fermentation and aging as lengthy as that of wine (one of the reasons lambic is considered a footbridge between the worlds of wine and beer).

Blended to taste: Lambic brewers manage the ever-changing flavors of aging lambic by blending old and young batches. Often sweeteners or fruit are added to subdue some of the lambic tang; sweetened or blended variants are regarded as styles in their own right:

Faro. A sweet, light table beer made by sweetening blended lambic with dark candy sugar and caramel.

Gueuze. A sparkling, fruity beer made by blending young and old lambic and then filtering and bottle-conditioning the mixture to achieve a naturally carbonated effervescence similar to that of champagne.

Fruit lambic. Made by re-fermenting young lambic with whole fruit (cherries, strawberries, peaches, grapes, etc). The fruit/lambic blend is generally matured for several months and then bottle-conditioned with another addition of young lambic.


The fascinating history of lambic has been covered in depth elsewhere by authors such as Martin Lodahl, Michael Jackson, and Jean-Xavier Guinard, and I will not revisit it here. Instead, I will attempt to decipher the lambic brewing process from a scientist’s perspective and translate it to a home brewing scale. This article represents a condensation of material gleaned from research papers and dissertations from Belgium, books and articles written by various other authors, personal accounts from people who have been to lambic breweries, postings from the internet’s Lambic Digest, and my own personal experiences. All aspects of the process of lambic production — from wort production to fermentation to blending and bottling — are included in the hope that this article may help other brewers in their attempts to understand and make authentic-quality lambic-style beer.


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A Style from Another Era


Some might say I live for lambics. As one of my favorite quotes from Michael Jackson says, “The lambic family are not everybody’s glass of beer, but no one with a keen interest in alcoholic drink would find them anything less than fascinating. In their ‘wildness’ and unpredictability, these are exciting brews. At their best, they are the meeting point between beer and wine. At their worst, they offer a taste of history."

Lambic is the product of some of the most idiosyncratic brewing methods in the world. Its production calls for unmalted wheat, old hops, and years of fermentation with wild yeasts and bacteria conducted in unsterile oak casks. Lambic stands out among today’s brewing standards more than ever as beverages of utterly unconventional, antiquated, and pretechnological charm.

Unfortunately, the beer’s artisanal appeal has not been fully embraced outside of connoisseur ranks. People are often shocked by the extreme flavor profile of real lambic or by the lengths required to recreate the style. Too often people immediately dismiss the beer as undrinkable and infected without really “tasting” it — not unlike the reaction of a hard-core Budweiser drinker tasting a Chimay for the first time. Even in the style’s backyard, shifts in locals’ tastes threaten the very existence of such treats as Cantillon Rose de Gambrinus or a Boon vintage-dated Mariage Parfait. With care and patience, however, the style may extend its native boundaries and thrive, in an adapted form, in the kitchens of dedicated home brewers.


Psychic Preparation for Lambic Brewing


Making a lambic-style beer at home can be as simple as boiling up some extract and hops and adding a few yeast and bacteria cultures. Or you can go to the extreme and use traditional turbid mashing schedules, spontaneous fermentation, and oak casks. As home brewers we have many choices; we do not have to follow tradition to the letter. Most of us do not live in Belgium, nor have we been making beer by this method for hundreds of years. Besides, innovation and creativity are the hallmarks of home brewing.

Based on my experience, however, the one key ingredient is time. No matter what recipe you follow, you can’t expect to have a product of character similar to any of the real lambic beers within a few weeks or even months. To do it right, you really need to wait at least a year before even bottling your beer or adding fruit to it, then another year or more while it further conditions in the bottle. (My Wild Pseudo-Lambic ale, which won the gold in the AHA’s national homebrew competition in 1994, was a year old when it was judged.)

Many brewers expect that they will have a product that is ready to bottle within a few months, and ready to drink within another few weeks. I have seen internet discourses, recipes from the AHA National Homebrew Competition, and even Jean-Xavier Guinard’s book perpetuating the belief in unnaturally short fermentation schedules.* Having spoken with Dr. Guinard, I realize that he and his publishers knew that few home brewers would even think about buying a book that had recipes suggesting the beer be allowed to ferment for a year or two and then undergo bottle conditioning for another year or more. Most brewers who have tried to make pure-culture lambic-style beer will agree that these published fermentation schedules are far too short to achieve a product with a character truly similar to the real thing.

*Jean-Xavier Guinard’s Lambic describes all aspects of lambic beer and brewing, including its history, its traditional production processes, and the breweries that still produce the style. It also goes into a fair amount of detail in outlining the microbiology of spontaneous fermentation and describes methods for making a pure-culture lambic-style ale at home. The information in the book is accurate and concise, with the exception of a few minor details (for example, I have yet to find a reference that indicates that Kloeckera apiculata have any proteolytic activity as described in the book). Those of us who have pursued this type of brewing have found the book to be an invaluable resource and an excellent stepping stone. I highly recommend Lambic to anyone considering making pure-culture lambic-style beer.

Just keep in mind that there is no such thing as “instant” lambic-style ale. The microorganisms used to ferment lambic grow very slowly and are equally slow at producing the flavor profile that gives the style its true depth of character. You cannot buy a kit or follow some recipe in a homebrew shop catalog and end up with a well-balanced, complex product of true Belgian character. Your beer is not going to develop Brettanomyces character or the proper acidity in a few weeks. It will not become a melange of flavor after two weeks in the bottle. The path to the Holy Grail may well take a lifetime.

Most important, understand that success is to a large degree a matter of chance and that you may fail, even after investing a great deal of time and effort into your beer and after following all the procedures meticulously. You can use traditional mashing techniques, use all the right ingredients, and add all kinds of wild yeast and bacteria, ferment in a cask for years, and still end up with an utterly disappointing product.

There is little you can really do to change what ultimately happens in the fermentation vessel. Either the beer will develop the classic Brettanomyces pellicle (film), ropy mouthfeel, and character — or it will not. Your beer may end up so acidic you will want to use it for cleaning calcium deposits off of your brew kettle, or it may be so mild that it barely passes as infected beer. Even after bottling, lambic-style beers can undergo large changes in flavor.

These precautions should not be taken as discouragement from brewing this most challenging beer style. These are merely the facts of lambic life. Belgian brewers manage this level of variability and uncertainty by strict adherence to traditional methods and by what may seem like a bit of a cheat — blending. All lambics are variable, and the art of successful commercial lambic brewing is in blending various batches to create a balanced, complex, and pleasing flavor profile.

My warnings are done. With a bit of effort and patience, anyone can produce a reasonable lambic-style ale in the home setting. What follows is a studied and emphatically positive account of lambic-style home brewing.


Wort Preparation


The grist: A lambic grist is usually composed of Pils-type barley malt mixed with 30–40% raw wheat. The most traditional method of working with the grain in lambic brewing is called turbid mashing. Turbid mashing is a time-consuming and labor-intensive process that was devised to effectively break down the proteins in ungelatinized raw wheat while leaving a good supply of starches and free amino nitrogen for the yeast and bacteria to feed on during the long fermentation. Home brewers, however, have various forms of wheat available to them, many of which can simplify the procedure greatly. The box, “Types of Wheat Available to Home Brewers,” describes the options. You can decide for yourself what works best in your brewery.


Types of Wheat Available to Home Brewers

Lambic-style recipes call for wheat as 30–40% of the grist. Traditional lambic brewers used raw wheat, which requires a complex mashing method to break down its proteins while leaving a good supply of starches and free amino nitrogen for the yeast and bacteria to feed on during the long fermentation.

Wheat is available to home brewers in various forms, including whole wheat berries (hard red or soft white varieties), flaked or rolled wheat, and malted wheat. The form you choose will likely be based on the equipment you have and how traditional you want to be in your recipe formulation.

Raw Wheat

Like any adjunct, wheat must be precooked somehow before mashing to gelatinize, or disperse, its tough starches so that the enzymes can work on them. Turbid mashing is one means of accomplishing this goal. You could, of course, pregelatinize your own raw wheat (see the “traditional turbid mash” and “shortcut mash” discussions in the Wort Preparation section of the main text).

Crushing raw wheat: If you work with raw wheat, you will have to deal with crushing it. Raw wheat is not friable because it has not yet been malted or kilned; it therefore has a tendency to squish rather than crush, making it difficult to mill, even with a roller mill. Running the wheat through a roller mill several times will help reduce it to fairly small particles. This is one instance in which a Corona-type mill (designed for grinding rather than crushing) may have an advantage over any of the various roller-type mills available. Because wheat has no husk, grinding it into a fine powder is not a problem.

Wheat flour: A few individuals have replaced the wheat fraction of the grist with whole wheat flour without encountering any problems with stuck mashes or slow runoffs. Of course, as they say, your mileage may vary. Whether or not this will work for you will depend on your mashing and lautering setup and your level of experience. If you feel adventurous, give it a try.

Rolled, Flaked, or Malted Wheat

Guinard suggests flaked or rolled wheat or malted wheat as alternatives to raw wheat. Wheat flakes and rolled wheat are pregelatinized, which makes for a less time-consuming mashing procedure. These forms of wheat can be found at most homebrew supply stores and often at natural food stores or cooperative markets, along with raw wheat of either the hard or soft varieties. Malted wheat also simplifies the mashing step and is usually readily available through most homebrew stores.


The mash: Whatever you choose for the grist, the goal is to produce a wort that is high in amino acids and dextrins and light in color. You can achieve this composition in a few different ways, from simple extract brewing to the complex traditional turbid mash method. Whether or not a turbid mash is required to achieve optimal flavor is a matter of debate, and not all lambic brewers use this method. However, two of the most traditional breweries, Boon and Cantillon, do.

The extract option. Tradition is nice, but you can make lambic-style beers even if you are not an all-grain brewer. The simplest approach to making lambic-style ale is to use dry or liquid malt extract. Since you need extra amino acids and dextrins in the wort to support the long fermentation, you may consider using an extract meant for making wheat beer. These are typically made from 60–70% malted wheat and are readily available. My prize-winning 1994 lambic-style beer was made using a wheat-based extract produced by Briess Malting Company called CBW Bavarian Weizen. If you wish, you can also blend 100% wheat extract with malted barley extract to achieve the traditional 30–40% wheat content.

If you use extracts, get the freshest extract possible and boil for a full hour to maximize the extraction of the hop antiseptic compounds and to precipitate the excess proteins in the extract. The main problems with extracts as a whole are that they generally produce beers darker than equivalent all-grain beers, and the extracts themselves may be somewhat nutrient deficient.

The all-grain option. If you are an all-grain brewer, you can use malted, flaked, or raw wheat in your mash and choose from a variety of mash routines. Probably the simplest grist comprises 30–40% malted wheat — which is easier to mill than raw wheat — with the remainder being two-row Pils or lager malt.

The grain can then be mashed using a single-step infusion in the 150–155 °F (65–68 °C) range to produce a reasonably dextrinous wort that is also very light in color. Or you could modify the mash schedule by using a step mash or decoction mash of the type outlined by Eric Warner. Warner’s technique helps break down the excess wheat proteins and provides the extra amino acids needed by the various yeast and bacteria. One problem, though, with such an intensive mash schedule is that it can lead to too much breakdown of the dextrins in the grist and thus too little carryover into the wort.

If you choose to use raw wheat, you have several options that traditional brewers didn’t have. Using pregelatinized flakes, or pregelatinizing the wheat yourself before the mash (see the “shortcut” mash method, below), can allow you to stick to simpler mashing techniques.

The traditional turbid mash. The goal of the turbid mashing procedure is to break down the larger proteins of the raw wheat and malt into free amino acids and to produce a wort high in dextrins and starches. The process of turbid mashing is somewhat like inverse decoction mashing; it involves removing the liquid portion of the mash, boiling it, and then reintroducing it to the whole mash (in decoction, the grain is included in the removed portion). This process of removing, boiling, and returning is repeated a number of times until the mash reaches saccharification temperature. After a two-hour saccharification rest, the wort is run off and the grains sparged with near-boiling water. The whole process is followed by a 4- to 5-hour boil that reduces the large volume of liquid, precipitates the excess proteins, and bursts any suspended starch granules.


A Scaled-Down Mash Schedule from Cantillon Brewery

The following is a homebrew-scale version of the Cantillon Brewery’s (Brussels, Belgium) turbid mash schedule. Based on the information presented in Martin Lodahl’s article, the Cantillon Brewery gets about 33–34 points/lb/gallon. The Cantillon grist is composed of 34% raw wheat and 66% malted barley. The recipe is scaled down here to yield 5 gallons of wort with an original gravity of 1.048 (11.86 °P), or 5 x 48 = 240 points. If we assume we will get 30 points/lb/gallon, then 240 ÷ 30 = 8 lb of grain. The barley malt fraction is 66% of 8 lb, or 5.3 lb of malt, leaving the remaining fraction of raw wheat at 2.7 lb.

The Cantillon schedule calls for mashing 1,300 kg of grain into 850 L of water (2,860 lb grain into 900 quarts water), or 3.2 lb grain/qt water, or 0.3 qt water/lb grain. Our 8 lb of grain therefore requires 8 x 0.3 quarts, or 2.4 quarts of water.


In all of the following steps, the temperature and water additions were taken directly from the Cantillon schedule as published and scaled accordingly.

    1)    In kettle #1, combine water (about 2.4 quarts) at 144 °F (62 °C) and the crushed grain to achieve a temperature of 113 °F (45 °C). Mix the grain and water thoroughly and allow it to rest at 113 °F for 10 minutes. This amount of water is just enough to wet all of the grain and flour. The mash needs to be stirred well to make sure that all the grain is wetted and that no clumps of flour are present. Total time for this step is about 20 minutes, including the temperature rest.

    2)    Next, add enough boiling water (212 °F [100 °C]) to the mash to bring the temperature to 136 °F (58 °C). Do this over the course of 5 minutes, making sure to mix thoroughly. It will take about 3.5 quarts of boiling water to raise the mash temperature to 136 °F, and you will end up with a very soupy mash with plenty of excess liquid. Allow the mash to rest for 5 minutes at this temperature. Remove about 1 quart of liquid from the mash, add it to kettle #2, and heat to 176 °F (80 °C). The liquid taken off should have the appearance of milk. Once heated it will clear up and large particles of hot break will form.

    3)    Add more boiling water to the mash over the course of 10 minutes to bring the temperature to 150 °F (65 °C), again with constant mixing. It will take about 5 quarts to achieve this temperature. Allow the mash to rest for 30 minutes at 150 °F (65 °C). At this point, the mash will be very soupy and the liquid much less milky in appearance.

    4)    Remove 4 quarts of liquid from kettle #1 and add it to kettle #2, which will put it up to 5 quarts. Continue to heat kettle #2 to maintain a temperature of 176 °F (80 °C). The liquid removed from kettle #1 will be very cloudy, but not quite as milky as the liquid previously removed in step 2.

    5)    Add more boiling water to kettle #1 to bring the temperature to 162 °F (72 °C) and allow it to remain at that temperature for 20 minutes. Again, it will take about 5 quarts of water to reach the rest temperature. The mash should be very thin and soupy with a great deal of small particulate matter in the liquid portion.

    6)    After the 20-minute rest, run off the liquid from kettle #1 and bring to a boil in a third kettle. Add enough of the liquid from kettle #2, at 176 °F (80 °C), back into the mash in kettle #1 to bring the mash to a temperature of about 167 °F (75 °C). Allow the mash to rest at that temperature for 20 minutes. If any liquid is left in kettle #2, it can be added to the previously collected runoff in kettle #3.

    7)    After 20 minutes, recirculate the wort in kettle #1 to clarify it, and begin sparging with 185 °F (85 °C) water. Sparge until the gravity of the runoff has dropped to less than 1.008 (2.06 °P). Boil the wort, now in kettle #3, until the volume is reduced to about 5 gallons.

    8)    As the wort begins to boil, hop with about 4 oz of aged hops. The combined water additions and sparging should add up to about 9 gallons of wort. Total boiling time to reduce this volume to 5 gallons will depend on your equipment and methods. At the beginning of the boil, the wort will be cloudy and full of large flocculent break material. As the boil proceeds, the wort should clarify as the proteins continue to coagulate and the starch solubilizes. After boiling, the wort can be cooled using your method of choice. This method of mashing does not seem to yield the large amount of break that a typical all-malt infusion mash would yield. As stated elsewhere, however, your results may vary depending on your equipment and technique.


A test batch using this method yielded a wort with an original gravity of 1.040 (9.97 °P). At about 25 points/lb/gal, the mash efficiency was not as high as that obtained at Cantillon, but the yield could probably be improved by extending the times for the various rest steps. It may also be a good idea to heat the liquid withdrawn from kettle #1 each time at a very slow rate. To play it safe, you may want to start out with a larger grain bill based on the more conservative yield of 25 points/lb of grain. Clearly, your own results will vary with your methods and equipment.


The Boon turbid method. A simplified turbid mashing method was proposed by Frank Boon of Brouwerij Frank Boon (a lambic brewer and gueuze blender based in Lembeek, the town south of Brussels that is considered the Tigris-Euphrates of lambic). Boon suggested mashing in at around 86 °F (30 °C) using as little as 0.5 quarts water/lb of grist. The mash can then be stirred and the milky wort run off and boiled for a few minutes. In the meantime, Boon recommends adding fresh water to the grist and performing a step mash of the brewer’s choosing. After the stepped mash reaches the 140 °F (60 °C) range, the boiled, milky wort is added back to the mash to raise the temperature to the saccharification range. Once this rest is completed, the wort can be run off and the grain sparged. This method also produces a large volume of liquid, again requiring the suggested 5-hour boil.

The “shortcut” mash. An even easier route would be to grind the raw wheat and then gelatinize it before adding it to the mash.

First, add water to the wheat at the rate of 1.5–2 qt/lb, then add 10% of the malted barley and heat the mixture to the 150 °F (65 °C) range, letting it stand for 15–30 minutes to allow the enzymes in the malt to act on the wheat starch and to aid in their hydration.

After the temperature rest, heat the whole mixture to boiling with constant stirring. Feel free to add more boiling water as the mixture begins to thicken. Be sure not to heat it too fast or stop stirring, or you will have a big, gummy, burnt mess.

After it has boiled for 15 minutes, add it slowly to the main mash (I prefer to have the main mash at 100 °F [37 °C]), stirring so as not to raise the temperature of the mash too quickly or unevenly. The temperature will settle in the 120–130 °F (49–54 °C) range, depending on the volume.

Then begin gradually to heat the entire mash to the various step temperatures.

A faster step schedule would be to rest at 130 °F (54 °C) or so for 15 minutes, raise the temperature to 145 °F (63 °C), hold it there for 15 minutes, and then raise it again to 152 °F (67 °C) and hold it for another 30 minutes, followed by mash-out and sparging.

The sparge: The sparging of a lambic mash is typically carried out with water that is hotter than customary sparge temperatures, usually close to 190 °F (88 °C). This temperature helps to extract dextrins and unconverted starches from the mash. The process extracts tannins from the malt as well, but these are precipitated out or broken down over the long fermentation cycle and do not contribute any significant astringency to the finished beer.

The use of hotter-than-normal sparge water is particularly important if you follow a true turbid mash–type schedule because of its poor conversion. Bear in mind that in conventional beer production, you do not want starches and tannins extracted into the wort, but in lambic brewing they are needed to support the long fermentation process and will ultimately be used by the yeast and bacteria. Without these usually undesirable products, the lambic organisms may not thrive, and the finished beer may not have the right flavor characteristics.

The boil: The boil should be vigorous and last 1.5–2 hours or longer, depending on the initial volume of the wort. The boil serves a number of functions, including the precipitation of excess proteins from the wheat and the reduction of the volume of liquid collected. The long boil in lambic brewing makes Irish moss or other clarifying agents unnecessary; any excess proteins that may remain in solution will either be used or precipitated during the lengthy fermentation process.

Hops: The hops used in lambic production should be aged for one to three years, to the point at which they have lost all of their bittering power and so do not detract from the acidic, pungent character of the beer. According to Dr. Roger Mussche of Destelbergen-Heusden, Belgium, aged hops also contain tannins that give lambic its dry, astringent taste, and antioxidants from hop resins allow the lambic a longer shelf life and help control levels of undesirable Gram-positive bacteria such as Bacillus, Sarcina, Streptococcus, and others (10).

The varieties typically used are of the low to medium alpha-acid range, such as Hallertauer, Tettnanger, or Brewers Gold. Almost any hop variety will do, though, with the exception of high alpha-acid varieties such as Chinook, which tend to retain bittering power and intense flavor even after long aging.

The aging process. Home brewers have a couple of options for achieving the effect of aged hops. Once again, you’ll have to reverse everything you’ve learned about hops and the importance of keeping them fresh.

One strategy is to buy fresh hops and leave them out at room temperature for a year or two, but this requires planning and is not convenient for the beginning lambic-style ale brewer. You or a friend may have some old hops that you just could not part with but that have never been used, and if these are old enough they may serve the purpose. Newer hops can be heated at low temperatures (<200 °F [<93 °C]) on a cookie sheet for 4–5 hours. The idea is to heat the hops until all of their aroma has been driven off. Be aware that the smell may not be one that others find pleasant.

As hops age they take on a very pale green to yellow color and lose all aroma; the lupulin in whole hops turns from yellow to orange-brown. They also go through a stage of smelling rancid and cheesy. This smell is unpleasant, so it is best to leave them in a well-ventilated area.

I have found that leaving hops outside in the Arizona summer sun for a week or two seems to do a very good job of aging them. And if you have a total aversion to “ruining” perfectly good hops you may be able to purchase end-of-the-year hops at a reduced price from your local homebrew shop or from one of the many homebrew mail order supply companies. Alternatively, the herb departments of many natural food or cooperative stores stock hops that are usually well-aged and devoid of aroma with well-oxidized lupulin glands.

Whether you choose to use whole or pellet hops does not seem to matter as long as the hops are well-aged. Both forms can be used alone and together, depending on what’s on hand. Crushing the pellets into powder will help to enhance the oxidation process. You may want to put the hops into a container with a fine mesh cover of some sort and shake the container every once in a while to enhance oxidation.


Next Step: Fermentation


The selection of hops is the last stage of the lambic brewing process over which you have a reasonable degree of control. Once your lambic-style beer begins the fermentation process, you have no option but to dig in and let the microorganisms do their work. Part II of this article will enter the world of lambic fermentation, starting with the principles of wort cooling and continuing with a map of the microbiological terrain of the lambic fermentor.


Part II — Fermentation and Culturing


For many, the real fun of lambic brewing starts with the fermentation process, where the beer becomes exposed to the various microorganisms that will ultimately give the beer the complex flavor profile unique to lambic beers. Traditional Belgian lambic brewers, of course, add nothing to their wort themselves, relying instead on various freely occurring microorganisms to work their magic and ferment the beer naturally. Modern brewers outside the style’s Belgian homeland have a bit more work on their hands to introduce the wort to the right organisms. At the same time, they may also have a bit more control over the process.

This second part of the series on brewing lambics at home describes the process and some of the techniques home brewers can use to emulate the complex chain of fermentation events that leads to a lambic-style beer.


Cooling and Spontaneous Fermentation


Traditional lambic wort is allowed to cool overnight in shallow coolships located in an open loft of the brewery (some modern brewers get help from fans). During this time the microflora living in and around the brewery inoculate the wort. These wild microorganisms, along with those present in the fermentation casks, are what create the hallmark flavors of traditional fermented lambic over the course of its complex one- to three-year fermentation cycle. One group of European researchers claim to have isolated 100 distinct yeast colonies, 27 colonies of acetic bacteria, and 38 colonies of lactic bacteria in a single type of lambic.

If you are a brave soul you can try your hand at spontaneous fermentation; this approach seems to have met with some limited success among home brewers here in the United States, but the usual result is not much like a real lambic. Until very recently, the desired blend of microorganisms could be consistently found in the proper balance only within the roughly 500 sq mile region surrounding Brussels and the Senne river valley — and then only during the months of October through April. Today, home brewers have access to these wild yeast and bacteria cultures and can introduce them to the wort themselves.

The flexibility of home brewing allows you to choose from a variety of traditional and modern adaptations. You can either combine open cooling with the addition of some pure cultures, or you can use your favorite wort chiller to cool the wort and then inoculate with the appropriate cultures.

You could also allow the wort to cool overnight in the pot it was boiled in, with the lid on. Though it may seem counterintuitive to leave the lid on the pot, it will ensure a somewhat sterile environment in which to pitch your desired cultures. The next day, siphon the clear wort off the trub into a fermentation vessel. The long, slow cooling of this method leads to the formation of large amounts of DMS in the wort, but the long fermentation process will scrub it all out.


Fermentation out of Control


The success or failure of a spontaneous fermentation is largely beyond the control of the brewer. The “wild” Brettanomyces yeasts and bacteria of the Pediococcus genus are slow-growing microorganisms that require special environmental conditions to grow. You can do your part by making sure the conditions are optimal for these organisms to grow, but then you must cross your fingers. It’s understandable, therefore, why some superstitious brewers have been known to painstakingly maintain or recreate the exact environmental conditions that made the last batch a success. (Guinard mentions one traditional lambic brewer who refused to remove his deteriorating roof for fear of removing valuable critters.)

Even under the best conditions, however, traditional lambic brewers have problems with some casks not fermenting properly because the various organisms either fail to thrive or grow too much. If the environmental conditions are not correct to start with or if they change too quickly, the relative populations of the various microorganisms may be affected and the resulting beer will lack the proper balance of flavors.

Modern brewers using cultures may feel they have a bit more control over microbiological growth, but there’s no reason to think it is any easier to avoid the risks faced by traditional brewers. The process is still new to home brewing, and fermentations are so long that conclusive recommendations cannot yet be drawn as to how best to introduce the cultures to the wort in the home brewery. One thing is known, however: As in any fermentation, it helps to start with healthy, fresh cultures and to provide them with the necessary nutrients to grow during the long fermentation process by exercising special care during the mash (see Part I for details on wort preparation).


The Process of Lambic Fermentation (Simplified)









Acetic acid

1 months





4 months




Lactic acid

3 months




Ethanol and esters

4 months


Any additional time left in fermentor for maturation of “old lambic flavor.”


In yet another affront to standard brewing practice, wort aeration is not really necessary when brewing lambic-style beers. The microorganisms will act at their own pace, and there’s no point in trying to accelerate the fermentation period. Any existing oxygen will be used very quickly by the enterobacteria that come on the scene first.


The Microorganisms at Work


The fermentation process is a fascinating tug-of-war between many different species of bacteria and yeast.

Enterobacteria start the fermentation chain by fermenting glucose and producing various acids, most notably acetic acid. Rising volumes of Saccharomyces yeast species eventually produce enough alcohol to kill off the enteric bacteria after about a month, beginning a primary fermentation that lasts about four months. Pediococcus bacteria then kick in with the lactic fermentation for about three months. Brettanomyces yeast then dominate for a “secondary” fermentation that accomplishes most of the rest of the attenuation during the next five months. At the end of a year or so, the beer is considered to be maturing.

Note that because of the “sponaneous” nature of this fermentation, this schedule can vary from batch to batch and from cask to cask. The ebb and flow of growth of the various organisms depends on many variables, including temperature changes and the changing levels of nutrients released and absorbed as organisms alternately proliferate and die.

This article focuses on these major microflora. Other types of yeast do traditionally come into play during the lambic fermentation process, but because their contributions are limited, they should not really be of concern to home brewers. Kloeckera apiculata, for example, are active around the same time as the enterobacteria and also succumb very quickly to rising alcohol levels. Their flavor contribution is minimal.* Other yeasts that come later in the process also contribute little to the character of the beer.

Enteric bacteria: During the first month of lambic fermentation, enterobacteria are the dominant microbiological presence. These bacteria grow rapidly and will affect the growth of subsequent yeast and bacteria. Their metabolic byproducts will also affect the character of the beer by contributing flavors variously described as celerylike, parsniplike, mushroomlike, smoky, or moldy. These flavors carry through the fermentation process. The bacteria’s various acid by-products (described in detail in the following paragraph) also affect beer flavor by contributing to the sour taste of the final product. The majority of acetic acid found in lambic beer, in fact, originates in the first month and is one of the by-products of enterobacterial growth.

The enterobacteria that have been found in lambic beer include Enterobacter cloacea, Klebsiella pneumoniae, Escherichia coli, Hafnia alvei, Enterobacter aerogenes, and Citrobacter freundii. These bacteria are motile (or “mobile”), Gram-negative straight rods (with the exception of Klebsiella, which are never motile). All of them ferment glucose; some produce gas. Most grow quite well in the presence of air and are also able to ferment lactose. These bacteria follow either a butanediol fermentation pathway or a mixed-acid pathway, which leads to large amounts of lactic (~1500 ppm), acetic (~600 ppm), and succinic (~275 ppm) acids and the formation of ~2,000 ppm of 2,3 butanediol in the first month of the fermentation. They can reach levels of 1 × 108 cells/mL during the first 30–40 days of fermentation.

Disease concerns dispelled. Some strains of enterobacteria can cause various forms of food poisoning in humans; Salmonella is the culprit in most cases. But because they are eventually killed during the fermentation process by rising alcohol levels, the enterobacteria found in lambic (which do not typically include Salmonella) are unlikely to pose a health threat.

“Kitchen “ inoculations. Research has shown that family kitchens often harbor more enteric bacteria than bathrooms. Meats, vegetables, and kitchen sponges or wash cloths have all been found to be highly contaminated with the same varieties of enteric bacteria found in lambic, with sponges and clothes having particularly high bacterial counts. While this may be bad news for those concerned about food poisoning, it may be good news for lambic brewers.

Merely turning on the water in the sink or squeezing rags or sponges can render the bactera airborne; thus the kitchen can be an ideal environment for the inoculation of lambic wort with enteric bacteria. You could simply leave the fermentor open near a kitchen sink for an hour or two after the wort has cooled, then wait an additional 24 hours before adding any yeast. This will allow the enteric bacteria to gain a foothold; they should quickly begin to grow and multiply to a level that allows them to produce significant amounts of metabolic by-products and to deplete the glucose in the wort.

Home brewers who fear enteric bacteria are missing an integral part of the production process. Studies indicate that enteric bacteria have a profound effect on the subsequent growth and flavor development in real lambic.

Saccharomyces: Saccharomyces yeast step in after a couple of weeks to take care of the beer’s primary fermentation, which goes on for three to four months. These yeast have little else to do with the lambic’s flavor profile. Most of the beer’s alcohol production thus takes place early in the process. The rising alcohol levels and subsequent drop in pH quickly bring about the demise of the enterobacteria.

Pediococcus: In traditional lambic brewing, Pediococcus damnosus is the dominant type of lactic acid bacteria found in the wort after about three months of fermentation. It is a spherical, tetrad-forming, Gram-positive bacteria. Pediococcus are described as a “homofermentative” bacteria because they ferment glucose to lactic acid without producing carbon dioxide. As the Pediococcus population grows, the concentration of lactic acid increases in the lambic to levels of 5,000 ppm or more. This increase in acid is a slow and progressive process that occurs over a number of months.

Pediococcus are very fastidious organisms, growing slowly with complex nutritional requirements. They can take advantage of nutrients given up by autolyzed Saccharomyces, but the concentration of Pediococcus cells in spontaneously fermented lambic is never very high — usually only 1 X 106 cells/mL or less, although cell numbers may be higher in artificially inoculated wort.

Concentrations typically increase during the relatively warmer temperature of the Belgian summer (normally below 80 °F (27 °C)). The lactic acid, diacetyl, and acetoin that the Pediococcus produce contribute to the complex flavor and aroma of lambic — particularly the acid; the levels of vicinal diketones (diacetyl and acetoin) in traditional lambic have been found to be at or below taste threshold levels. It’s the Pediococcus that can be responsible for the early “ropiness” that is found in some lambics.

Brettanomyces: Brettanomyces is considered one of the major yeast species responsible for the flavor characteristics of lambic. The pure-culture species most home brewers typically use in their lambic-style beer are either Brettanomyces bruxellensis or B. lambicus. These yeast usually have ellipsoidal cell shapes but can also be cylindrical or elongated. They frequently form chains and pseudomycelium. These filamentous branched cells float, forming a pellicle (film) on the surface of the beer. Most lambic brewers religously try not to disturb this film, which is believed to serve as an oxygen barrier that prevents oxidation. The pellicle will sink if disturbed.

Brettanomyces yeast have the ability to form acetic acid from glucose under aerobic conditions (when they grow on calcium carbonate agar, the acid forms a visible zone of clearing around the colonies. They demonstrate a negative Pasteur effect; that is, they produce more alcohol under aerobic conditions. By contrast, Saccharomyces show decreased alcohol production under aerobic conditions. In lambic brewing, though, little oxygen is available during the secondary fermentation to take advantage of this fact. Brettanomyces’ other advantage over Saccharomyces does affect lambic: Brettanomyces yeast have cellular dextrinases that allow them to use dextrose polymers larger than the typical trisaccharides used by Saccharomyces; in other words, they can break down existing dextrins that Saccharomyces cannot.

A Brettanomyces culture has a characteristic acetic, earthy, horsy aroma. (Some people claim there are differences between the various Brettanomyces strains.) These yeasts grow much more slowly than do Saccharomyces brewing strains. Most brewers classify Brettanomyces as “wild” yeast and typically do all they can to avoid them. In most modern beer styles these yeasts leave unpleasant phenolic, smoky, and goaty off-flavors. In lambic beer, of course, these are desired characteristics.

Another unique aspect of Brettanomyces is its ability to enzymatically catalyze esters from alcohol and acid. Thus ethyl alcohol and acetic acid can be combined to form the ester ethyl acetate and lactic acid can be combined with ethanol to form ethyl lactate. These are two of the primary esters desirable in lambic beer.


Culturing and Maintaining Lambic Organisms

Yeast and bacteria cultures can be purchased from a number of retail suppliers, yet many brewers, especially those who brew frequently, may wish to maintain their own cultures. A great deal of reference material exists about how to culture Saccharomyces yeast (see Further Reading at the end of the article). The other major fermentation players, Brettanomyces and Pediococcus, are more difficult to culture, requiring very specialized nutrients and environmental conditions. I strongly suggest that you have a solid background in yeast culturing techniques before attempting to culture these microorganisms. Furthermore, unless you are planning to brew lambic-style beers more than once or twice a year, it’s probably best to get new cultures each time.

Neutralizing Acids a Key

Both Brettanomyces and Pediococcus need to be maintained on media that can help neutralize the acids they produce as metabolic by-products; otherwise, the acid will cause a large drop in pH and the organisms will die.

The most readily available food-grade acid-neutralizing agent is calcium carbonate (CaCO3), also called precipitated chalk. A concentration of 2% (2 g/100 mL) in the growth media or agar will provide adequate buffering capacity.

Calcium carbonate is essentially insoluble, though, which can present problems if it is used in making wort agar because it will fall out of solution before the agar solidifies. To prevent this from happening, cool the wort/agar solution to 113–122 °F (45–50 °C), swirling constantly, before pouring it into the tubes or dishes. When culturing in liquid media, however, you can gently swirl the media with the culture growing in it once or twice a day to help prevent any stratification of the acid in the solution and to aid its neutralization. As the lambic organisms grow in the liquid media, the acid produced will react with the calcium carbonate, which will become solubilized over time. Even when a culture reaches maximum confluence, some unneutralized calcium carbonate may remain, but this is nothing to worry about because the acid produced by the growth in the main wort will dissolve it over time.

Brettanomyces culturing: Brettanomyces yeast can be grown on a wort agar that incorporates 2% calcium carbonate (as noted previously). A successful wort should also have a specific gravity of about 1.040 (9.9 °P) and is preferably made from an all-grain wort (a malt extract wort may lack proper nutrients). Brettanomyces, because of their fastidious nature and acid by-products, need to be transferred to new slants more often than do Saccharomyces (at least every two months is desirable). Longer intervals between transfers may result in cultures that are no longer viable.

Note on contamination: Frequent manipulation of the slants obviously increases the risk of the yeasts themselves becoming contaminated with other yeasts, molds, or bacteria. Sterile culture techniques and attention to details are important.

If your culture does become contaminated, you can prepare a dilute suspension of the yeast and streak it out on a petri dish containing wort agar with 2% calcium carbonate and 10 µg/mL cycloheximide (using appropriate caution). Generally only non-Saccharomyces yeast will grow on media with cycloheximide in it. Any others that do grow and that have zones of clearing around them are likely to be colonies of Brettanomyces, which create this zone in the otherwise opaque, white agar as they dissolve the calcium carbonate. You can then pick the colonies off and reculture them on cycloheximide-free media.

The technique described here is by no means a definitive technique for the isolation and characterization of Brettanomyces. Yeast such as Kloeckera ate also acid producers that will grow on cycloheximide agar. If you have doubts at all, you may be better off buying new cultures and/or locating a microbiologist who will work for homebrewers. The only absolute way to characterize a culture is through extensive fermentation, assimilation, and morphological testing — don’t believe anyone who tells you otherwise.

Pediococcus culturing: Pediococcus bacteria are more difficult to grow and maintain than Brettanomyces yeast because of the complexity of its nutritional and environmental requirements. Pediococcus grows best in liquid rather than solid media, which increases the risk of unseen contamination. (For this reason, unless you have access to a 1,000X power microscope and plenty of culturing experience, it is recommended that you do not try to maintain Pediococcus at home for any length of time.)

MRS broth. MRS (deMan, Rogosa, and Sharpe) broth is the preferred medium for growing and maintaining Pediococcus over long periods. It is a rather expensive defined medium, but it provides the necessary nutrients and buffers for optimal growth over extended periods. It is available with preparation instructions on the package. A minimum suggested interval between slant transfers is one month. Allow the culture to grow for a week at room temperature and then store it at 39–40 °F (4 °C).

Stab cultures. Another method for storing Pediococcus is the use of stab cultures. Prepare the MRS medium using 1.5% agar and put it into tubes. Then, using a needle or inoculation loop, “stab” into the tubes of solidified media to inoculate it with bacteria. Allow the bacteria to grow at room temperature for a week or so until signs of growth can be seen. The tubes can then be stored at 39–40 °F (4°C).

Whether you use liquid or stab cultures you need to keep the tube caps screwed down tight to limit air diffusion into the cultures and to prevent desiccation. Pediococcus are not gas producers, so gas buildup is not a concern.

Note on hop resistance: Bacteria can sometimes lose their hop resistance if grown in unhopped media for extended periods. Therefore, if you are going to try to keep cultures going over a long period of time it is suggested you add iso–alpha-acids to the media using some type of hop extract (whole or pellet hops cloud the media with particulate matter and are less than ideal for monitoring growth visually). A suggested level is the 15–25 IBU range.

Contamination risks: The same caveats apply to bacteria culturing as apply to lambic yeasts — you will need the proper equipment and good sterile technique. If you are serious about culturing lambic microorganisms, you might consider using a laminar flow hood of some type to allow you to work in a nearly sterile environment. Fungi Perfecti (Seattle, Washington) is one of several companies that sell them; alternatively, the article by Jim Caldwell in the “Further Reading” section offers advice on how to build your own.


Lambic Pitching — “Throw Caution to the Wind”


When, and how much to pitch: With pure-culture lambic, brewers have a number of options regarding when and how to add the various microorganisms, ranging from simply adding all the cultures right after cooling, to adding each organism separately at various times to attempt to effectively mimic the spontaneous fermentation growth cycle.

The whole process is further complicated by the question of what size inoculum to use: Should you try to duplicate the traditional method, where the initial number of cells per milliliter of wort is very small, or should you use larger cell numbers to ensure the proper growth of these microorganisms?

Unfortunately, the brewer has no definitive way to ensure the balanced growth of all the organisms. A number of individuals have recently tried varying the starter size as well as the addition schedule, but because lambic-style ales take so long to develop, the results so far are inconclusive. These issues have no simple answers, and again, many techniques have been, and need to be, tried.

Fortunately, lambic brewers can generally throw caution — and their worts — to the wind. I’ve tried several different schedules myself and have concluded that pitching all at once is probably fine. If enterobacteria are involved, it may be wise to pitch all starters after a day or so to allow the enterics to do their work before alcohol levels start to rise.

Similarly, the volume to pitch is not likely to be a source of concern. Though most beers require a large volume of yeast to ensure a rapid fermentation and to decrease the risk of contamination by wild yeast and bacteria, large starters are not required for lambic. If the yeast and bacteria are healthy, they should have no problem growing in the wort in the small volumes described in the next section. Remember: This beer will be in a vessel for a year or more, and the bacteria and yeast will have plenty of time to grow. Also, as the acid-producing strains grow they will kill off any other organisms by lowering the pH and available sugars and by increasing the alcohol. If you feel the need to use larger starters to put yourself at ease, then by all means go ahead. Just remember the beer will still take a year or so to develop the proper character.


Propagating Your Starter


Whether you choose to culture your own lambic microorganisms or buy them, you will need to propagate them individually before adding them to the wort. The following routine assumes you have decided to add all of the microorganisms at the same time.

A wort with a specific gravity of 1.040 (9.97 °P) mixed with 2% calcium carbonate (CaCO3) will work just fine for propagation (the CaCO3 neutralizes the acid the organisms produce that may prevent them from growing). You may also want to add some hops to achieve a range of 15–25 IBUs. Saccharomyces starters can be created as with any other beer.

Following a scale-up procedure will reduce the risk of other organisms overgrowing the cultures, although with lambic cultures you do not have to make as large a starter as you would with the yeast starters typically used for normal beer. Begin with a volume of ¼ oz (~5 mL) of wort and allow the culture to reach confluence (peak population density, like a high kräusen). When it has, add the contents to a volume of 4 oz (~100 mL) of wort and allow it to again reach confluence. At this point you can either pitch the culture or scale up one more time to a volume of 1 pint (~450 mL) of wort. Such procedures have also been outlined elsewhere.

Points to consider: Brettanomyces. Be aware that Brettanomyces is a very slow grower compared with other yeast and generally does not develop a large kräusen head. The starter should develop a typical Brettanomyces aroma as the yeast begins to produce fermentation by-products. You will notice a distinctive acid aroma as well as aromas often described as horsy or mousy. A taste of the starter should reveal the acidic, mousy, earthy taste associated with Brettanomyces. As the yeast grow, the acid produced will help dissolve the calcium carbonate until the fine white calcium precipitate disappears.

Pediococcus. You may want to add 10% apple or tomato juice to the wort starter to satisfy the additional vitamin requirements of Pediococcus. An alternative is to use 0.5% dried brewers yeast, which also provides the desired nutrients. Yeast extract is even better (it is pure and soluble), but it is expensive and can be difficult to find. Wort from a previous brewing session with 0.5% yeast extract added works well, giving a nice clear medium in which you can easily monitor the growth of the bacteria. As the bacteria reach confluence, a clear zone will develop at the top of the liquid; the rest of the liquid will be clouded with bacteria.


Fermentation Conditions


Use a single vessel for optimal nutrition: Several key factors will determine the amount of microbiological growth the wort is capable of sustaining. If you followed the guidelines for wort preparation in Part I, you will already have a wort high in dextrins and unconverted starch. Once you have cooled the wort and inoculated it, allow it to remain in one vessel for the entire fermentation process. This runs counter to the typical practice of racking the beer to a new container after primary fermentation is complete, but by not racking you retain the nutrient-rich trub and autolyzed yeast, which will provide nutrients for the Brettanomyces yeast and Pediococcus bacteria. It has been shown that once the Saccharomyces has done its work, the majority of B vitamins and amino acids have been removed from the wort, suggesting that the yeast act as a storage depot for these nutrients, which are later used by the other microorganisms.

Fermentation temperature: Temperature control has never been a part of the traditional lambic brewing process. It is therefore not as crucial in lambic brewing as it is with other styles of brewing, which is a lucky thing because you may find it difficult to find an ideal temperature environment that will remain consistent throughout the long fermentation period. Nonetheless, a truly dedicated brewer with the means for temperature control could choose to emulate the actual temperatures in Belgium as much as possible. Discussions on the internet with fellow enthusiasts may provide some helpful insights here.

Many lambic-style brewers find that simply keeping the beer on the cooler side and trying to avoid extreme temperatures and fluctuations works adequately. A temperature that is too high or too low may lead to insufficient or excessive growth of one or more of the various microorganisms. In Belgium, the temperature of the lambic cask rarely exceeds 77 °F (25 °C), and many visitors note that Belgium is generally pretty cool most of the year. (One visitor observed that even in April the Boon Brewery felt cold.) Cold temperatures may help prevent excessive acidification of the beer by the yeast and bacteria while encouraging the other flavor characteristics to develop.


Fermentation Vessels


Lambic-style beer can be fermented in a number of types of vessels, ranging from standard food-grade plastic buckets to the finest quality European oak casks. Wooden casks are the fermentors of choice for traditional lambic brewers, but they may be difficult to find, expensive, and hard to work with. This section provides an overview of the advantages and disadvantages of the alternatives.

Traditional oak barrels: The advantage of oak casks over other vessels is that the porous wood provides nooks and crannies for the various yeast and bacteria to inhabit and allows a slow diffusion of air into the fermenting wort, which may further aid microorganism growth and flavor development. After a cask has been used for a number of batches it will become, one hopes, infected with the right microflora, thus further aiding in the production of a more authentic product.

The wood may also contribute various flavors from previous batches of beer. Additionally, even old oak may add a certain minor astringent note to the lambic from the slow leaching of any remaining tannins in the wood.

Purchasing casks. Lambic brewers may have fewer problems than other brewers in finding inexpensive, suitable secondhand casks. Because of wood’s inherent tendency to harbor ghosts of flavors and microorganisms past, preinfected casks shunned by Brettanomyces-phobic winemakers or brewers may be available on the market for a steal.

While residual critters may be desirable, you don’t want, or need, to add other flavoring to your lambic. Therefore, uncoated wine barrels are usually best because the insides have been lightly browned rather than charred as are whiskey barrels. Used casks, or new casks that have been properly aged, may have already had much of the oak flavor leached out. It’s also possible to accelerate the aging process with chemical stripping.

Condition. Remember that these vessels will be holding your beer for a year or more, so it’s important to keep them in good condition. Keeping them filled when not in use wards off leaks and mold. Cleaning with metabisulfite inside and out will inhibit mold and mildew growth. It would be a shame to have a cask well-infected with Brettanomyces or Pediococcus, but ruined by mold.

Jason Dunson-Todd’s article, “Beer from the Wood” on page 60, provides more on the history, purchasing, and care of oak barrels.

Other types of fermentors: Other materials offer both advantages and disadvantages over the use of wood. One questionable difference between the vessels is their relative levels of gas permeability and its effect on lambic fermentation. The question may well be moot, however; studies show that in a given vessel the majority of gas diffusion occurs through the closure and its sealing surface (stopper or lid), and not through the vessel walls (18). So consider the relative merits of the alternatives as well before purchasing.

Ironically, the commonly found food-grade plastic vessels may bear the closest resemblance to traditional cask fermentors because, like wood, these containers are somewhat permeable to oxygen and other gases. Containers made from high-density polyethelene (HDPE) can range in size from 5 gallons up to drums of 15 gallons or more. These vessels have the advantages of being inexpensive, lightweight, and practically unbreakable. The material used to make 5-galIon plastic water bottles, polycarbonate (PC), is harder and more rigid than HDPE and is about twice as permeable to oxygen and carbon dioxide (19). PC is also a clear plastic, which allows you to observe the fermentation process over time — an advantage for brewers curious about the development of the pellicle, or for monitoring the pearly ropiness that may develop in their lambic-style ale.

Bear in mind that both types of plastic vessels are relatively soft and can be especially susceptible to scratches, which may then harbor wild yeast and bacteria produced during the fermentation process. This may be to your advantage, of course, if you are really willing to “throw caution to the wind” with your lambic-style ale.

Home brewers generally consider glass to be the best fermentor material because it is inert, easily cleaned, and inexpensive. Glass does not allow gas diffusion, but it does allow brewers to observe the fermentation process and the various stages that a lambic-style beer goes through over the course of time.

Stainless steel has the advantages of inertness, strength, and ease of cleaning. It is relatively expensive, however, and completely opaque. Even if you have an extra pot or keg to ferment in, you must remember that it will be unavailable for other uses during the year or more it takes to ferment to completion.

Oak chips: What about the missing oak qualities if you’re using a different type of fermentor? The contribution oak casks make to the flavor of lambic is considered to be minimal because the casks used in lambic brewing are often decades old and have probably had the vast majority of tannins and phenolic compounds leached out of them. Some people still feel, however, that the oak may add some astringent quality to the lambic. For these brewers an alternative to the cask may be oak chips.

Oak chips are usually available from homebrew shops or can be specially ordered. You may wish to use toasted chips and soak them in a couple of changes of boiling water before using them in the fermentor to help remove the majority of the oak flavor compounds from the wood (you do not want beer that tastes like an oaky Chardonnay). Preliminary experiments indicate that after the chips are exposed to lambic-style ale the microorganisms invade the pores of the wood. This was shown by washing the “infected” chips thoroughly with sterile water and then adding them to sterile wort, which later developed Brettanomyces and Pediococcus colonies. This area is still wide open for experimentation.


One to Three Years down the Road


Fermentation of a lambic-style ale will require one to three years of patience, but eventually might just achieve the kind of tangy, special character that makes the wait worthwhile. The final installment of this three-part series flashes forward to visit the final product with a discussion of how to bottle, blend, and preserve your accomplishment.


Part III — The Finishing Touches


Art and science meet in the final stages of lambic brewing. This installment concludes our three-part series on brewing lambic at home with a review of the flavoring, blending, and bottling techniques that can make or break this complex beverage.

You’ve waited patiently for a year or more while your lambic-style ale has gone through its wild paces. A complicated procession of wild yeasts and bacteria have fermented your unconventional concoction into a highly unique drink. It’s lambic, but it’s not necessarily finished.

It is at this point that traditional lambic brewers may infuse their beers with fruit to create a classic cherry kriek* or a raspberry framboise. Many brewers will go on to blend old with young lambic to make “gueuze,” one of the most tantalizingly complex beer styles. Bottling adds the final flavor and conditioning characteristics, presenting special challenges in itself.

These final steps can be as important to the character and drinkability of the beer as the primary ingredients and aging of the base beer. Pulling them off with proper panache involves, as do most aspects of lambic brewing, a disciplined mixture of fancy and formula.


Bearing Fruit in the Finish


Many people think of fruit-flavored beer when they hear the word lambic. And in fact, most of the lambic sold in the world today is flavored with fruit in one form or another. The challenge for any brewer of lambic-style ales is to achieve a product that has good lambic-like qualities along with balanced fruit flavor. For many lovers of traditional lambics, an ideal product is something like a Hanssens Kriek or a 1986 Boon Framboise Mariage Parfait. These beers have assertive lambic quality and excellent fruit flavor, but no tooth-aching sweetness.

Fruit can be added in any of several forms, but the more traditional lambic brewers use real (whole) fruit in their beers. Real fruit, however, is both expensive and time consuming, and many brewers now choose to use fruit juice concentrates or extracts instead.

Many pasteurize their fruit lambic to stabilize the fruit flavors and to retain sweetness. Pasteurization prevents the Brettanomyces from continuing to ferment various residual sugars and dextrins. (Left unchecked, Brettanomyces will ferment the beer down to an original gravity of 1.000, thus stripping the beers of their big fruit flavor and aroma.) It is not unheard of for lambic brewers to add sugar to the beer to bring out even more sweetness in the fruit, blend it with very young lambic for flavoring, force-carbonate it for marketing purposes, and then pasteurize it to remove the possibility of any further fermentation. Though flavor may be the final arbiter, one can’t help but feel that such a product is very far removed from traditional lambic.

Generally the brewers who follow more traditional techniques allow the fruit lambic to continue fermentation in the bottle, resulting in a much drier, less fruity product. The two approaches toward fruit lambic result in products that appeal to entirely different drinkers.

Pick your fruit: The traditional fruits of choice for lambic brewers have always been cherries (kriek) and raspberries (framboise), but now you can find lambic flavored with any number of fruits, including peach, strawberry, and banana. Some lambic brewers will use almost any fruit under the sun, including exotic flavorings (notably coconut), and are able to achieve highly flavored products by using fruit juices and syrups. Some fruits work better than others, however. My experience shows that strongly flavored, tart fruits such as sour cherry, raspberry, or possibly blackberry seem to work best; less intense fruits simply do not stand up to the flavor of lambic-style ale or to the refermentation process.

To emulate the methods of traditional lambic brewers, use plenty of real fruit of the best quality you can find. You can use fresh, frozen, or canned fruit, as you wish. You may also want to look into the various fruit purées that are available. (F.H. Steinbart in Portland, Oregon, carries fruit purées from Oregon Fruit Products [Salem, Oregon] in individual sizes; many varieties are available.) On average, it appears that Belgian brewers typically add about 2 lb of fruit/gallon of beer (see Table I on page 30, “Fruit Dosing Schedules”). If you are adding fruit juice concentrate, you will need to add to taste; large quantities will probably be required for full fruit flavor. (I’ve found, however, that using extracts with chemical additives in large quantities can result in some undesirable flavors.)

Methods for adding fruit to the base beer: Start by racking the base lambic-style ale into a larger vessel; for example, from a 5-gallon to an 8-gallon vessel. This will provide extra volume for the fruit and headspace as fermentation begins again.

The lambic-style ale you use as the base beer should be at least one year old and should show some potential of being a nice beer on its own, without fruit. Believe me, you are not going to make a silk purse out of a sow’s ear by adding fruit. Do not use a beer that is excessively acidic or “hard” as the base. If you need to, blend it with some younger, “softer” beer instead, or even with an unfermented, unhopped ale (though this second option is less traditional). Fruits such as raspberries contribute their own acidity to the beer, and starting with a too-acid beer just seems to make matters worse.


Table I: Fruit Dosing Schedules

The following list of fruit dosage schedules from three Belgian breweries shows the variability of practice in commercial use today. As a guideline for home brewers, use about 2 lb of fresh fruit per gallon.



Amount (lb/gal)








Mariage Parfait (all fruit)















Let the beer settle for a few days after racking, and then add the fruit. Add it carefully! Excessive aeration from splashing may encourage acetobacter contamination. One way to minimize splashing is to rack the beer onto the fruit. Whether you crush the fruit or not will probably have little effect because the various microorganisms should be able to break it down after a few months. And if the base beer is healthy and normal — by lambic standards — it will contain the right mix of Pediococcus and Brettanomyces to prevent the growth of any unwelcome microorganisms that may be present on the fruit. Just to be on the safe side, though, make sure any unprocessed fruit you use is clean and free of mold and dirt.

The beer may take three to six months to ferment, depending on the amount and form of the fruit added (it takes longer to extract flavor from whole fruit) and the strength of the yeast. If the beer is not bottled immediately, fermenting at cool temperatures (60 °F [16 °C] or less) slows the growth of microorganisms without impeding the extraction of flavors from the fruit. If using whole fruit, the beer will need to be racked to another vessel for a few more weeks to allow any large pieces of suspended material to settle out.


A Glossary of Lambic Brewing

Brettanomyces: The yeast responsible for a lambic’s secondary fermentation, which kicks in after about eight months. Considered an unwelcome “wild” yeast in almost any other beer style, Brettanomyces can consume dextrins, which Saccharomyces cannot, and produces alcohol, carbon dioxide, and the esters that give lambic its unique horsey flavor.

Enterobacteria: Main producers of acetic acid early on in the fermentation process. Rising alcohol levels kill them off after just a few weeks.

Faro: A young lambic blend; traditionally includes added sugar.

Framboise: A raspberry beer (usually a lambic).

Gueuze: Lambic blend of aged (one year or more) and young (less than six months) beer. The infusion of young beer leads to a secondary fermentation that traditionally results in a dry, light-bodied, and sparkly beer. Typically 5% alcohol (v/v).

Hard lambic: An “assertive” lambic containing high levels of acetic acid. Lambic may become hard early on due to enterobacterial activity. It can also become acetic later in the process due to acetobacter contamination or Brettanomyces metabolism gone awry.

Kriek: Though it could refer to any Belgian beer containing cherries, it is most often used in reference to traditional cherry lambics. Slightly higher alcohol (~5.5% [v/v]) due to refermentation by the fruit.

Lambic: Complex traditional Belgian beverage made with barley, unmalted wheat, and aged hops, fermented with wild yeast and bacteria, generally over a period of years. Typically 4–5% alcohol (v/v).

Lees: Sediment. Also referred to as dik-dik.

Mars: Rare version of faro, only about 2% alcohol (v/v).

Pediococcus: The bacterium responsible for the lactic acid fermentation of lambics, which kicks in at around 3–4 months.

Saccharomyces: The yeast responsible for lambic’s primary fermentation, producing the majority of alcohol in the beer.

Soft lambic: A kindler, gentler lambic, less sour than a “hard” lambic, and possibly containing more lactic acid.


When you’re satisfied with the flavor, rack the beer yet again and move on to your next step, which would be either blending, if you’re making a gueuze, or straight on to bottling. Note that if you’re using fruit juice concentrate, you could conceivably add it right before bottling and allow it to ferment right in the bottle.

Cheat with sweets: Based on some limited experimentation, it appears that sweetening an overly sour fruit beer helps to bring out the fruit flavor. The problem is that as long as the beer contains live microorganisms, they will ferment any sugar you add.

I have been told that one traditional lambic brewer adds unfermentable sugar in the form of saccharin to the beer at bottling time to help it retain its fruit character without pasteurization. Saccharin works well when added to lambic in the glass to counter lambic’s natural acidity. If you try saccharin, dissolve it in a small amount of water and add a few drops to a glass of beer to see how you like it (many people find that a little saccharin goes a long way). Some find the flavor of saccharin too “chemical” in nature. So before you decide to add saccharin to five hard-won gallons of beer, test it for concentration and flavor suitability.


The Variability of Lambic Fermentations

The data below illustrate just how unpredictable a lambic fermentation can be. All three beers came from the same brewery. The “soft” and “hard” beers were both from the same batch of wort and were nine months old. The “ropy” beer was six months old.





Alcohol (g/100 mL)








Real extract




Ethyl acetate (ppm)
















Isoamyl acetate




D-amyl alcohol




Isoamyl alcohol




Ethyl lactate




Phenethyl alcohol




Acetic acid




Lactic acid





Another option if you plan to add sweetener is to sterile filter (0.2 micron) the beer before adding fruit (whole, syrup, or extract). This is the advanced home brewers’ alternative to pasteurization as a method of arresting fermentation. If you use whole fruit, allow the filtered beer to extract the fruit flavor for a few weeks. Then fine the beer to help precipitate the fruit sediments, and add sugar as needed before kegging it or counterpressure-filling bottles (you will have to artificially carbonate your beer). This is a good method for achieving a product with the appropriate balance of lambic and fruit qualities. It is far from being traditional, but, after all, we are home brewers and can do whatever we want. Just remember to call it a lambic-style ale, not a true “lambic.”


Side-Stepping Cross-Contamination

All brewers are concerned with sanitization and worry especially about bringing wild yeast and bacteria into their breweries, whether by accident or design. Home brewers may have less cause for concern, however, because carboys, buckets, hoses, and other equipment can all be dismantled and completely exposed to cleaners to eliminate any wild yeast and bacteria (professionals don’t have this luxury).

Over the past three years, I have brewed all my beers, including lambic-style ales, using HDPE and PC plastic containers, and cross-contamination has never been a problem — but then, I take great pains to make sure not only the equipment, but the brewing environment (counters, sinks, walls, and floors), are as clean as possible before and after each brewing session. Cleaning and sanitization are of paramount importance when intentionally introducing “wild” organisms into your brewery.

  • Clean and sanitize all equipment thoroughly before and after each use.
  • Make sure all equipment is free from any dirt and grime and that you’ve chosen the appropriate sanitizer.
  • Clean containers that have held beer for a year or more especially well. Automatic dishwashing detergent works well for this task because it contains trisodium phosphate (TSP) and sodium hypochlorite and thus contributes a preliminary sanitization step. After cleaning, soak the container overnight in your favorite sanitizer and rinse it out the next day.

By following good cleaning and sanitization practices you should not have to worry about cross-contamination, but if you want to be sure, keep a dedicated set of equipment for lambic-style beer brewing. For a more thorough discussion of cleaning and sanitization you may want to consult some additional references (see the article by Maribeth Raines and the article co-authored by Jim Liddil and John Palmer in the “Further Reading” section).


The Art of Lambic Blending


In Belgium, lambic producers are often referred to as both lambic brewers and gueuze blenders. The dual title recognizes the importance of blending in creating delicious products. No two batches of lambic will turn out the same, nor will any single batch remain the same over time; often the only way a producer can manage these shifting flavor characteristics is to mix and match batches of varying ages.

Blending serves other purposes as well as melding flavors. Traditional lambics are bottle conditioned to become a gueuze product, and the blending process is critical in achieving the proper level of carbonation in the bottle. An addition of young, active lambic (generally fermented about 6–12 months) can rejuvenate old “flat” lambic (usually fermented for two years or more), bringing new fermentables that inspire still another fermentation and add carbonation in the bottle, resulting in gueuze.

The gueuze of the traditional Belgian lambic brewers is typically a 50:50 blend of young and old lambic, resulting in a Champagne-like beer, bottle-conditioned until it sparkles with effervescence.

Accounts differ on the blend at the Cantillon Brewery in Brussels; according to some, the brewery uses a 70:30 blend of old and young beer, others, including Jean-Xavier Guinard, claim that Cantillon blends a third each of one-, two-, and three-year-old beer. Cantillon’s definition of “old” and “young” lambic is fairly typical — two years for the old and six months for the young.

Things are done a bit differently at the Boon Brewery. Frank Boon has a slightly more disciplined view of the world — one in which the ideal lambic product is consistent, good-looking, and long-lasting. To this end, Boon gueuze is made by blending mostly old beer that has fermented at least two years with a smallish amount of very young beer that may have been fermenting for as little as a few weeks. The blending ratio, according to Bone, is a surprisingly high 95:5. Boon also clarifies the old beer before blending. His technique results in a bottled product that is reasonably clear and free of haze and ropiness (haze and ropiness are two qualities he does not consider illustrative of “brewing art”).

At Lindeman’s, gueuze is made by judiciously blending the lambic of one summer (young lambic) with old lambic in such a way that the different flavors are balanced and that enough fermentable sugars (extract) are obtained to give the desired CO2 content. Gueuze created by this method of targeted blending is regarded as “real” gueuze. Gueuze made by adding sugar to the lambic is not considered an authentically traditional product.

The home brewer’s dilemma: Home brewers who wish to blend their beers are faced with the dilemma of needing to have two batches going simultaneously, one old and one young. The lengthy fermentation period, however, allows plenty of time to start up the second, younger batch. Another way around this challenge is to participate in a group effort (try it with your homebrew club). Still another variation, as mentioned already, is to substitute some standard, lightly hopped, unfermented ale for the young lambic (though traditional lambic brewers are loath to do so). Or, you could ferment a 5- or 10-gallon batch in 1-gallon bottles and hope the resulting beers all differ in character to some extent.

Whichever way you choose, you will need to know the potential extract of each beer and the present gravities of both batches to determine the ratio that will give you enough fermentables to achieve proper carbonation. Then you’re off to bottling.


Put a Cork in It — Bottling Your Beer


Unlike most other beer styles, lambic continues to change for the better with age, quite often becoming more complex and less harsh. As a lambic-style ale referments in the bottle, chemical reactions create important flavor changes. These reactions occur at a fairly slow rate because many of them are catalyzed by enzymes from Brettanomyces. Remember Brettanomyces grows slowly and never reaches very high concentrations in the fermenting beer or in the bottle. Be patient — your beer may have another six months or more to go.

In Belgium today, bottling methods for lambic, and particularly gueuze, vary. As stated earlier, many brewers artificially carbonate, sweeten, and pasteurize their beer to produce a more consistent, less aggressive product with wide market appeal. The ratio of old to young beer or to top-fermented ale is typically fairly low in such beers. The more traditional brewers use a more even blend of young and old lambic (Frank Boon’s high ratio of 95:5 is an exception); the beer is then bottled and allowed to referment for up to two years before release. Cantillon’s lambic may spend only six to seven months in the bottle, but generally reaches a level of 90% attenuation.

Although bottling is the traditional packaging method for lambic brewers, you could also try putting your beer into kegs or other containers that can be artificially carbonated, such as PET bottles fitted with a Carbonater. Or you could, of course, choose to naturally condition your beer in a keg and just use CO2 to serve it.

Refermentation of lambic in the bottle can provide adequate carbonation for the beer (though some commercial examples are nearly flat). Blending, even with a young standard ale, can provide new fermentables, but as explained earlier you would need to experiment with the quantities of the blend to achieve your desired carbonation level (2.5–3 volumes). If you don’t blend, the beer will need to be primed as with any other beer to provide food for the yeast.

Microbiological troubleshooting: The problem with bottle conditioning a beer that has been fermenting for so long is that the number of viable carbon dioxide–producing organisms may be very low. The levels of Brettanomyces never do get very high during the course of the fermentation, and depending on your racking and filtering techniques the numbers remaining at this point may well be insufficient. If this is the case the beer may not become carbonated at all, or will carbonate only very lightly.

A related problem is that the dominant microorganisms in the beer by the time you bottle may be bacteria rather than yeast, and these bacteria will use the sugar before any yeast can get to it. Because most of the bacteria you’ll find in an older lambic-style ale are likely to be of the homofermentative variety that do not produce gas when they metabolize sugars (Pediococcus, for example), you will get little carbonation from this refermentation.

You may be able to combat these problems by preparing a fresh starter of Brettanomyces or Saccharomyces at the time of bottling. You may also want to add a dose of the heterofermentative Lactobacillus; some symbiosis between the yeast and bacteria apparently aids in carbonation. (Be prepared for some foaming of your bottles as the yeast kick off.)

It may seem counterintuitive to add Saccharomyces because this strain generally doesn’t survive the lambic fermentation process, but there may be some commercial precedent: a recent analysis showed that the only yeast recoverable from a Boon lambic was indeed a yeast not resistant to cycloheximide, most likely Saccharomyces. This makes some sense, because Boon fines his old lambic before adding the young beer and Saccharomyces is the dominant strain in the early stage of the fermentation (Saccharomyces comes from young beer). Limited testing indicates that this yeast can indeed tolerate the levels of acid and alcohol in the beers to this point.

Another approach would be to remove the bacteria by filtering at the 0.2-micron level before bottling. Then all you need to do is add fresh yeast and sugar for bottle conditioning.

Racking: If the beer is fairly old and has a thick pellicle of yeast on the top and a large layer of yeast sediment, it would be a good idea to rack the beer before bottling. Transfer the beer to another vessel, being careful to leave as much of the top and bottom layers behind as possible. Then let the transferred beer settle for a week or so. The idea is to reduce the amount of sludge that gets transferred to the bottles while leaving enough yeast in the beer for the refermentation. With luck, enough yeast will be left after racking to your bottling vessel to adequately carbonate the beer. The downside of all this racking, as already mentioned, is the increased risk it poses for acetobacter contamination.

Bottling from a cask. Lambic-style beer takes so long to ferment and age that when you bottle is not critical. If you are using a cask for fermentation, the critical issue is keeping the cask full to keep it from drying out and to ensure that all the microflora in the wood remain intact and happy. A good guideline is to coordinate bottling with the brewing of a new batch so that the cask is filled up again immediately. The day you brew you can transfer the contents of the barrel to carboys or other holding vessels, leaving behind as much of the lees, or sediment, as possible. Racking at this time also gives the beer chance to settle until you are ready to bottle. Then you can rinse the sediment out of the cask and have it ready to fill when your wort is cooled.

If you must empty the barrel and cannot fill it immediately, rinse it with water, burn a sulfur candle in it, and bung it up tightly. Alternatively, you can fill it with metabisulfite solution. Then when it is time to brew, rinse the cask well and fill it with wort.

Priming: Corn sugar can be used for priming just as with any other beer, a cup or so per 5-gallon batch. Dry malt extract (DME) is another option, as is maltodextrin powder; these contain little glucose and maltose and so are not a source of food for bacteria but will eventually be hydrolyzed into fermentable sugars by the Brettanomyces cellular enzymes. Standard priming rates can be used for DME and maltodextrin because, given enough time, they will ultimately become primarily fermentable sugars. Once you’ve primed, simply bottle the lambic and wait for it to condition.

Bottles and corks: There a reason why lambic breweries typically use thick champagne-style bottles and corks — they’re less likely to explode when carbonation levels exceed expectations. Cork is, of course, somewhat oxygen permeable, but the CO2 levels should be high enough that contamination or staling won’t be a factor. Inserting corks can take some practice. Number 10 or 11 (oversized) corks can be softened for insertion by soaking them in warm water that has been pre-boiled. Grolsch bottles may be a decent alternative. Regular crown caps may be OK if you’re confident about CO2 levels. Sanitize them first by soaking them in your favorite sanitizer (don’t boil them as that can damage the cap seal, particularly oxygen barrier seals).

Remember, as a home brewer, you have a great deal of latitude. It is possible that none of these approaches is practical for you. Making lambic-style beers, however, is not about being practical or making beer in the easiest manner. You’ll have to make decisions based on what you want to achieve and how many sacrifices you are willing to make to produce a beer that has any of the flavor and complexity of the real thing. It’s up to you.


The End of a Long Road


Brewing lambic-style ales can be as easy as boiling up some extract and throwing in some cultures, or it can be as true to tradition as can be achieved outside of an authentic Belgian brewery. The main thing to remember is that regardless of what you do, the beer will take time to ferment and develop the right flavor profile. You will need to be patient, whether you turbid mash or simply throw together a store-bought kit. You may be rewarded with an outstanding end product, and then again you might not.

Lambic is a surprising and unpredictable drink, best brewed with an open mind, a creative spirit, and — if necessary — the willingness to forgive. Undertaken positively, lambic brewing can steer your hobby down new avenues you will find well worth taking.

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