Lambics are spontaneously fermented beers native to the Senne Vally and Pajottenland regions of Belgium. Lambics are made from barley malt and unmalted wheat (30-40%) and aged hops. They form the base of a number of lambic products including unblended lambic, gueuze,fruit lambics including kriek and framboise, and faro. Lambic (and the lambic products Gueuze and Kriek) labeled 'Oude' or 'Vielle' are protected in the EU and are required by law to meet certain conditions including average age, minimum OG, max pH, max bitterness, max isoamyl acetate level . In practice the presence or absence of this term can help the consumer determine which products will likely be back-sweetened and which will be traditional, though some notable producers do not follow this nomenclature.
Lambic is brewed only in the fall and winter (generally from roughly October through March). Specific producers have differing feelings on when production can begin (some look for nights of 8C or cooler, others look for the first frost). The reason generally given for brewing lambic only in the fall and winter is for the proper ambient balance of microbes, though it also has to do with appropriate cooling overnight since ambient exposure is the only cooling form used in a traditional lambic. Additionally, inappropriate cooling overnight may favor the metabolism of undesirable thermophilic microorganisms, which could act in combination with the ambient microbe balance to result in the necessary fall and winter time window for lambic production.
Mashing and Boiling
Lambic grist is composed of a barley malt such as pilsner malt and a large percentage of unmalted wheat (30-40%). This grist is carried through a multi-step, labor intensive mashing process known as a turbid mash. During turbid mashing, a portion of unconverted starchy wort is removed from the mash and heated to denature the enzymes. This starchy wort is typically added back to the main mash after conversion of the main mash and is carried to the boil without full conversion. The starchy wort supplies wild yeasts and bacteria with carbohydrates that Saccharomyces cannot ferment.
This starchy wort then goes through a long boil (on the order of 4 hours) where it is heavily hopped with aged hops (on the order of 2.5-3g/l (~49 minutes in)). For hopping techniques/rates/timing, see Hops in Lambic.
Cooling and Fermentation
Lambics are spontaneously fermented, meaning that they do not receive any pitched cultures. Hot lambic wort is pumped from the boil kettle to a coolship, a shallow vessel with a large surface area to volume ratio, where it cools overnight open to the air. During this time the beer is inoculated with microorganisms from the environment and resident in the brewery. Lambic is only brewed the late fall, winter, and early spring when nighttime temperatures are sufficiently low to cool the wort appropriately overnight. The morning after cooling the lambic wort is transferred to barrels or foeders where fermentation occurs slowly over the course of months to years. Lambic fermentation is characterized by distinct phases when different microbes are active.
Related MTF threads:
- Discussion about the effects of the coolship versus barrels, including thoughts from Pierre Tilquin.
Lambic is traditionally blended (with other lambic and/or with lambic aged on fruit) before being sold, and it is uncommon to find straight (unblended) lambic for sale.In the lambic producing world, there are both blenders and brewers. Brewers produce lambic wort and all of the current brewers also blend their lambic. Blenders do not have a brewing facility and buy wort from other producers. This wort has been inoculated in the brewers coolship and is delivered to the blenders on the morning after brewing, where it is aged in the blender's barrels. There are currently 4 main lambic brewers supplying their wort to a blender and all but one of the current lambic blenders buy their wort from more than one producer.
Packaged unblended lambic is available from some producers. Notably Cantillon (Grand Cru Brucsella, noteworthy in that it is a 3 year old lambic), Girardin (lambic bag in a box) and Oud Beersel (lambic bag in a box ~1-2 years old), and De Cam Oud Lambiek (3 years old). Lambic from other producers is available by the glass in select cafes in Belgium.
A spontaneously fermented unblended beer that is indigenous to the Senne Valley and Pajottenland of Belgium. The flavor is dominated with a unique tartness and brettanomyces character from the wild yeast and bacteria that inoculate the brew. Unblended lambics are not carbonated, though some bottled products may develop carbonation over time. At very young age (months), lambics may have significant undesirable characteristics and may even be undrinkable. This generally passes with time as intermediates are re-processed and/or converted into more desirable characters. Younger lambics have less acidity than older lambics. Old lambics may display more prominent barrel character.
Average alcohol by volume (abv) range: 5.0-7.0%
Gueuze (also written geuze) is a blend of lambics, traditionally 1 year old, 2 year old and 3 year old which undergoes bottle conditioning to become a highly carbonated product. Some producers release blends labeled gueuze that involve blends of lambics of different ages than 1, 2 and 3 years. Not all producers follow the oude/vielle protected name designation and some traditional gueuze can be found without the label Oude or Vielle. Gueuze is generally highly carbonated from either the presence of unfermented material in one of the blend components, the addition of priming sugar, or both.
In the case of Fruit Lambics, whole fruits are traditionally added after the visibly active stage of spontaneous fermentation has finished. Some producers choose to add fruit to an older lambic (1-2 years old) while others choose a younger lambic (< 1 year). Kriek (cherries) and Frambroise (raspberries) are the most common fruit lambics, although other fruit lambics can be found including plum (e.g. Tilquin Quetsche), Apricot (e.g. Cantillon Fou Foune), wine grape (e.g Cantillon St. Lamvinus and Vigneronne) strawberry (e.g Hanssens Oudbeitje) among others. Once the fruit is added, the beer is subjected to additional maturation before (generally) blending in unfruited lambic and bottling. Alcohol content tends to be around 6%, although certain fruits such as grapes may raise the abv. Bottled fruit lambics are typically carbonated, though some uncarbonated fruit lambics can be found. Some fruit lambic is also available as bag in a box (Girardin Kriek).
A number of non-traditional sweetened fruit lambics can be found. These may sometimes be identified by especially low abv (<3%). Breweries producing sweetened lambics frequently use fruit / sugar syrups rather than whole fruits.
Average alcohol by volume (abv) range: 4.0-7.0%
Lambic outside of Belgium?
Eventually, anyone who ventures into the realm of sour brewing comes across the passionately defended appellation of Belgian lambic. While Belgian lambic brewers assert that lambic can only be brewed in Belgium, there is no question that comparatively good spontaneously fermented beer can be made outside of Belgium. Similarly, production methods employed in lambic (e.g. turbid mashing, using aged hops, etc.) are not inherently tied to a region. However not all spontaneously fermented beers are true lambics, according to the tradition and culture of the Belgian brewers who have preserved this historical brewing practice. And turbid mashing or using aged hops does not inherently lead to mixed fermentation. So this section deals with the ethical, personal, and legal considerations that brewers may need to factor in when determining whether or not to call their beers lambic.
In the EU, lambic has some legal protections  (English translation). for example it must be a spontaneously fermented product. That means that any beer receiving any pitched microbes (from lab cultures or bottle dregs) cannot be called lambic. Although this has no legal binding outside the EU, this is a fundamental characteristic of lambic and any brewer who decides to call their beer lambic should follow spontaneous fermentation. Some lambic brewers claim that the microbial terroir within Belgium is what gives Belgian lambic it's unique flavor profile, and this is another reason that lambic can only be brewed in Belgium. However, one study has shown that American coolship beers brewed at Allagash in Maine, USA, contain a very similar set of microbial players (see lambic.info for more information). Lambic producers have made it clear that while they encourage others to spontaneously ferment, they do not approve of the use of the term lambic for beers made outside of Belgium (~20 min in). While lambic has no legal protection outside of the EU and EU laws do not give lambic a regional designation (unlike other alcoholic products such as Champagne and Kölsch), many brewers outside of Belgium chose not to call their spontaneous beers lambic out of respect for the Belgian lambic tradition. Some brewers choose names alluding to lambic such as Sonambic (Russian River) or label their spontaneously fermented beers with the term Coolship (Allagash) to convey to consumers that their lambic-inspired beers are spontaneously fermented and follow parts of the lambic tradition without actually using the terms lambic or gueuze  (~6 min in). See also Dan's youtube video discussing using the term lambic.
There are also arguments that are contrary to the idea that only spontaneous beer brewed in Belgium should be labeled as "lambic". For example this includes Matt Humbard's argument that lambic brewers themselves aren't upholding their own traditions, and that "if it looks like a duck and quacks like a duck then it is a duck, regardless of what nest it was in when the egg hatched." Another example is that Funk Factory Gueuzeria also makes an argument for using the term "American Lambic" for it's spontaneously fermented beers.
In summary, there are many differing opinions both inside and outside of Belgium as to what can be called "lambic". While most commercial brewers in the USA choose to respect the wishes of Belgian brewers and avoid using the term "lambic", we encourage all brewers to educate themselves on all sides of the argument and to name their beers with thought and integrity.
Recommended MTF threads which include comments from many commercial brewers, including Pierre Tilquin:
What About Homebrew?
Noticeably, homebrewers tend to have a habit of calling any homebrewed blond sour beer a "lambic". This might stem from a lack of education about Belgian lambic and why many people respect the wishes of Belgian lambic brewers to not use the label of "lambic" for beer brewed outside of Belgium, as well as the BJCP Guidelines. However, the BJCP makes no claim that protected appellations should not be respected, and clearly states that the style guidelines are strictly for competition purposes only. In fact, for the sake of competition, every beer style should have the word "-style" appended to it, but that would be rather redundant from a competition guideline point of view (see section .iv of the 2015 BJCP Guidelines).
As with the naming of commercial beers as "lambic", there are many opinions on whether or not homebrewed sour beer should or should not be labelled as "lambic". While using the label "lambic" is an easy way for homebrewers to communicate that they've brewed some sort of sour beer, such labels are often harshly criticised by traditionalists in the sour brewing community and connoisseurs of lambic. Ironically, another sign of this potential misuse of the term "lambic" by homebrewers is that when a homebrewer makes a 100% spontaneously fermented beer, they usually will not call it a "lambic" to avoid it being confused with the typical sour brewing process which involves pitching lab cultures. Successfully homebrewing a 100% spontaneously fermented sour beer is not an easy feat, and great pride is taken by homebrewers who achieve success with 100% spontaneous fermentation. Other homebrewers still choose to call their 100% spontaneously fermented beers "lambic" because they were brewed using the exact same process as the Belgian lambic brewers.
For many traditional brewers, the term "lambic" or even "lambic style" not only carries a cultural tradition but a specific process as well, so when brewers use the word "lambic" or "lambic style" to describe their beers that are not brewed using the lambic process, a simple miscommunication is bound to occur between the traditionalist and the more competition-minded brewer. This liberal use of the term raises simple process questions such as is a homebrewed "lambic" fermented with a mixed culture product from a yeast lab, spontaneous fermentation, a mixture of wild and lab yeasts, kettle soured then pitched with Brettanomyces, or brewed in a bucket or an oak barrel? For the sake of discussing specific brewing processes, the word "lambic" has almost lost its meaning in the brewing competition world. Process matters a lot less in brewing competitions than it does for brewing and drinking culture. This is an increasingly important point when discussing brewing process considering that the term "lambic style" has been encouraged in many homebrewing circles instead of "lambic", especially for brewing competitions. Therefore, when discussing brewing process of a particular beer, the use of the word "lambic" is at the very least confusing and vague unless more specific brewing process information is provided.
That all said, labelling homebrew as "lambic" has little consequence other than potentially forming a habit that some sour beer producers (and fellow homebrewers) might find disagreeable. We encourage all homebrewers to educate themselves about the production of Belgian lambic beers, as well as the arguments for and against labelling homebrew as "lambic" and deciding for themselves which philosophy to endorse. The words "lambic" or "lambic style" might have a totally different meaning to a traditionally minded brewer, while the term "lambic" might have a more generic "brewing competition" meaning to others, and so for the simple sake of communication, clarification should be considered for any in-depth process related discussion.
Additional Articles on MTF Wiki
- Spontaneous Fermentation
- Turbid Mash
- Dimethyl Sulfide
- Gueuze and Lambic Character
- 3 Fonteinen
- De Cam
- Flanders Red Ale
- "Flemish Red Brown Beers", Presentation by Rudi Ghequire at CBC 2012. (Contains differences with Lambic)
- CRAFT Beer: Quantitation of the Major Components of Commercially Available Sour Beers Using Time-Domain CRAFT Analysis of 1H NMR Spectra.
- "Questions on the role of hulls, hay, and hops in the mash"; historical perspective on lambic mashing by Dave Janssen of Hors Catégorie Brewing blog. See also this MTF thread on experiences using hay/hulls/hops during mashing.
- "The Art of Spontaneous Fermentation", presentation by Frank Boon, 08/05/2017.
- EU law for Oude or Vielle lambic and gueuze
- The Sour Hour Episode 11 with Rob Tod and Jason Perkins from Allagash, Jean Van Roy from Cantillon, and Vinnie Cilurzo from Russian River
- European Commission. Agriculture and Rural Development. Legal protections for Lambic Beers. 1997. Retrieved 03/16/2016.
- The Sour Hour Episode 11 with Rob Tod and Jason Perkins from Allagash, Jean Van Roy from Cantillon, and Vinnie Cilurzo from Russian River
- Sour Beer Panel, Firestone Walker International Beer Fest