Brewing Lambic

Brewing

Raw Ingredients / Preparation

    Today's modern lambic is brewed using a grain bill of roughly 30% raw (ungerminated) wheat and 70% malted barley. Different breweries sue slightly different ratios for their own unique recipes. In most cases, both the wheat and the barley are coming from Belgian or German farms.
   Another important ingredient is the hop. Traditionally, hops containing low amounts of alpha acids are aged for anywhere between a year and three years; although some bales of hops wind up aging much longer. The hops are typically stored in an environment where they are susceptible to drastic temperature changes, such as an attic.

Mashing

    In order to mash, the grain must be crushed to expose the inside of the kernel. This is achieved by a grain mill which will pulverize the grain to a powder while leaving the husk in tact which will aid with sparging and draining.

The grains are sent to a vessel called a mash tun and mixed with water of varying degrees of temperature. The mash tun will serve as a place to convert the starches from the grain into sugars. The mash tun is a kettle shaped vessel usually containing multiple rakes made of metal that rotate around the tun and are powered mechanically. This aids in mixing of the mash as well as draining excess liquid after the mash is complete. Lambic undergoes what is known as a turbid mash. A turbid mash is a time-consuming method of conversion but is necessary to break down larger proteins, providing yeasts and bacterias with more food. This will result in a beer that is perceived to be drier in taste. Freeing the wheat of its amino acids will result in a higher dextrin content, giving the final product a fuller mouth feel. Different organisms will feed on different materials at different rates, providing another layer of complexity. This is opposed to a single-step mashing schedule where the grain rests at one temperature for an extended period of time. Single-step infusion results in less complex materials for organisms to break down.

An example of a turbid mash schedule is as follows:

Mix water and grain to reach a rest temperature of 45C/113F for 10 minutes. Add water to reach a rest temperature of 58C/136F for 5 minutes. Extract a portion of "milky" liquid from the mash and transfer to a kettle for heating to 80C/176F. Add water to reach a rest temperature of 60C/149F for 30 minutes. Extract a portion of "milky" liquid from the mash and combine with the previous liquid. Add water to reach a rest temperature of 72C/162F for 20 minutes. Begin draining wort into a separate kettle for boiling. Transfer "milk" back to mash and stir. Begin sparging (rinsing) grain with water at 85C/185F.

Sparging

    Sparging is a process of rinsing remaining sugar from the grain after the initial runnings of wort. This is done with near boiling water which will halt the enzymatic conversion process. These second runnings are then combined with the first runnings into one batch.

Boiling

   Lambic boils can last upwards of five hours. Historically some boils have lasted days but modern practices run anywhere between 2 hours and 5 hours. Boiling serves a few purposes. One is sterilization of the wort. Other purposes are caramelization of the wort thanks to maillard reactions and also a reduction of volume which provide a higher sugar content and thus increased alcohol content.

Hopping

    Boiling is also when hops are added. The brewer will make a hop addition as the kettles are being filled, before the wort actually begins to boil. Other than being aged, the hops are usually Belgian, Czech, or German grown hops typically of the Hallertauer variety. It is important to use hops with low alpha acid content as brewers are not looking for bitterness or acid contents; only the antimicrobial properties contained within the hop. This will prevent undesired molds and bacterias such as Acetobacter from inhabiting the wort.

Cooling/Inoculation

    After boiling is complete, the wort is sent through a filter (often a simple metal screen) to clear the wort of major hop and trub debris. This slow process will eventually drain the wort into a vessel called a coolship (koelschip). Coolships often reside in the brewery's highest most point next to slatted windows so that the cool night air can deposit hosts of microorganisms that will ferment out the wort into lambic. This process can only happen during the cooler months of the year due to the fact that molds have a difficult time surviving the cold temperatures. It will take the wort a period of about 10 hours to cool to the desired temperature at which point it will be transferred to barrels.

Barrels

Barrel Selection

    Lambic breweries do not like fresh barrels. Used red or white wine barrels are preferred. Most of the oak character has been stripped from the barrel, so not much will come through in the final lambic taste. Larger barrels or foudres are preferred over smaller barrels. These barrels are typically made from oak, chestnut, or cedar. 

Initial Fermentation

    The wort is transferred via hose into the barrels through the top bung hole. Barrels are completely filled and loosely capped with a silicon or wooden cork. In some cases a tubing system will serve as an overflow into buckets for when initial fermentation begins; making it easier to clean up after the barrels. Fermentation will typically occur within a few days, but can take up to a couple of weeks to begin. Factors involving that include temperatures during inoculation or temperatures during those first few days in the barrel. Organisms work more quickly at higher temperatures.

Resting

    Lambic will develop and rest in the barrels for between a year and three years in most cases. Some experiments have led to lambic resting for upwards of five years though. As lambic ages in the barrel, it matures. It takes on a more complex profile as different yeasts and bacterias interact, die off, rearrange esters and fermentation byproducts, etc. The lambic's sugar content is decreased over time and it becomes drier. It will also take on more of the barrels character due to longer exposure time and will oxidize.

Topping Up/Maintenance

    Most barrels are topped up only once after initial fermentation has completed and there is a significant airspace between the lambic and the bung. After most CO2 production has been completed, the barrels are hard-bunged and left to rest indefinitely.

Fruiting

Fruit Selection/Preparation

    The most commonly used fruits in lambic production are cherries (Kriek) and raspberry (Framboise, Frambozen). Many other fruits are used. Ex: blueberry, gooseberry, apricot, cloudberry, currant, blackberry, apple, peach, banana, pineapple, sea buckthorn, and a variety of wine grapes. Traditionally whole fresh fruit was steeped in lambic of minimum one year but modern practices include using frozen fruit or fruit extracts/juices.

Duration

    In most scenarios fruit is placed in a stainless tank and lambic is transferred on top to rest until secondary fermentation has ceased. This may be as quickly as four weeks or as long as eight weeks. Most fruits are placed in whole without being crushed or pitted. Only in the case of apricots is half of the fruit portion placed onto lambic with its pits removed, half in. 

Once fermentation is completed, the now fruited lambic is transferred to a bottling tank through a filter. The filter could be cellulose or any other type of filtering material.

Blending

    Fruit lambics are typically not blended with other fruit beers. In some events, if the lambic shows too much sign of fruit (over-fruiting), the brewer will blend in some unfruited lambic to mellow the flavor. 

Gueuze/geuze is loosely defined as a blend of 1, 2, and 3 year old lambics. This ratio is very dependent on the blender's intentions, what barrels are available to choose from, and what those barrels provide in terms of flavor profile. Generally speaking (and never a steadfast rule): 3 year lambic will be softer and more mellow, providing a nice base. This is used in lower proportions. A 2 year lambic will provide the most character and interesting nuances in a blend. This is used in slightly higher amounts. A 1 year lambic will provide fresh, active yeasts to further develop the blend once it is bottled, along with more fermentable sugars for bottle fermentation. This is used in the highest proportion. Again, this is not always the case. Sometimes a brewer may choose to use any age lambic in a much higher proportion than outlined here. The process is guided by tasting and smelling barrels. The final blend must be close in range to a desirable gravity in order for bottle refermentation to occur.

Storage

Bottling

    Depending on the sugar content (gravity) of the final blend/lambic, sucrose sugar may be added in small amounts to provide food for yeasts to feed upon in order to aid in the creation of carbon dioxide within the bottle. This is adjusted according to the level of desired carbonation.

During the bottling process, lambic is sent from the stainless steel bottling tank, typically fed by gravity. The bottling machine may be primitive or very modern, depending on the brewery. Bottles are often not flushed with CO2 to prevent oxidation. Lambic bottles are thick walled, reinforced, Champagne styled. Green or dark brown in color. The bottles are filled to the arch of the neck and topped with either a wine or 'mushroom' styled cork. In the case of a wine cork- a metal crown cap is applied to prevent the cork from popping out during the production of CO2 within the bottle.

    Bottles are left unlabeled until time for sale. Storage conditions vary from brewery to brewery but there are two schools of thought on bottle aging. Some breweries store their bottles on their sides in a pyramid fashion; making one layer against a depression in a brick wall, reversing the orientation of the next layer, and repeating the pattern all the way to the ceiling.

Other breweries will store their bottles vertical in cases until time for sale. In both cases, bottles are left for a minimum of three or so months. Most blenders prefer to age their bottles for minimum six months before sale, especially in the case of geuze. This will allow bottle conditioning to occur, along with any strange phases in viscosity to clear up. (Pediococcus byproducts known as 'ropiness')