The secrets of <span>lambic brewing</span>

The secrets of lambic brewing

At Lindemans Brewery in Belgium’s Senne River Valley, we have maintained the same level of quality and craftsmanship for six generations. Scroll to discover the stories and secrets of the lambic brewing process at Lindemans Brewery.

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6 generations of lambic brewing heritage

Visitors to our historic Vlezenbeek brewery can't miss the old Lindemans farm-brewery, built in 1856. The façade dates to 1877 but curiously, it was the 7781 vintage that was sealed in the brick. Had the workers who made the façade had too much lambic to drink perhaps? The explanation has been lost to time! The old brewhouse is home to a beautiful open, red cast iron vat, the predecessor of today’s equipment. While this iconic vat was decommissioned in the early 1990s, it almost didn’t make it past the 1930s!

War threatens the brewery

During WWII, Lindemans Brewery faced a tough choice. As in World War I, when copper equipment and barrels were confiscated by advancing troops, they had to find a clever way to protect it. The Lindemans family secretly submerged it in a nearby pond, where it remained hidden throughout the war. Afterward, the family recovered and painstakingly restored the water-logged vessel. A remarkable story of resilience, ingenuity, and passion for tradition!

The modern lambic brewhouse

Wander through Lindemans lambic brewery and around every corner you will discover the secrets and ingredients required to produce our lambic beer. In the inner courtyard, the grist mill houses the machines that grind the malt and wheat. Dried, aged hops wait patiently, stacked in bags and stored nearby. Water, an important brewing ingredient, comes from our private well more than 90m below the brewery.

The current brewhouse was built in 1992 and has a capacity of 18,500 litres of wort per brew. The pumps, valves, and mixer that produce our lambic beer are on the ground floor. On the upper level are four spectacular copper vessels: the mash tun, the mash kettle, the filtration tun and the boiling kettle.

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The mash tun

The sugars necessary to produce lambic beer are extracted from the ground grains in the mash tun (70% malted barley and 30% wheat). The brewing water and the grains form a paste that is brought to a variety of temperature levels, with water added at each level. This allows the starch to be extracted from the grains, producing a milky solution. At 78°C the starch is converted into fermentable sugars by the action of enzymes. These are the sugars that will be converted by fermentation into alcohol flavour and aroma components.

A portion of the milky solution produced in the mash tun is transferred to the mash kettle via two filtered drains. In this vessel, the temperature increases to 90°C. This temperature rise generates a broader spectrum of fermentable sugars. The resulting sugar profile supports an extended fermentation period, lasting at least one year or even longer.

The filtration tun

The filtration tun is where the insoluble components of the grains, called the hull, are separated from the sugar solution, or the wort. The hull is deposited onto filtration plates and forms a cake that filters the wort which then goes into a pot. The leftover residue or 'draf’ contains an excess of natural fibres. It is sold as nutritious livestock feed to farmers in the region.

Once the wort has passed into the boiling kettle, the cooking phase can begin. Aged hops of 2-3 years old are added during this step. They act as a preservative, not a flavour additive, so that lambic can be stored and aged. The exact cooking time (between three and four hours) depends on the wind and density of the evaporating vapour. Before it is poured into the cooling tray, 10% of the brew - more than 2,000 litres of each 18,500 litres brew - disappears as vapour.

The boiling kettle

Lambic and the art of spontaneous fermentation

After cooking, the wort is brought to the huge cooling tray, called the coolship. This is the most mysterious aspect of lambic brewing. At night, the wind and the local microflora inoculate wild yeast into the wort as it cools. Since this happens without human intervention, it is called beer of spontaneous fermentation. The next day, the wort is pumped into the fermentation vats. Through a variety of successive fermentations, the wort slowly turns into lambic. This occurs in large oak barrels called foeders (foudres) or in stainless-steel vats with added wood chips, similar to processes used in the wine industry. During the first six to seven months, fermentation converts the sugars into alcohol, taste and aroma components.

Learn about what makes lambic unique

After the fermentation process, it is time for the maturation process to begin. This will last at least six additional months or as long as several years. The characteristic taste of lambic beer develops during this stage. Lindemans Brewery often has more than 6 million litres fermenting and maturing at any given time: the equivalent of 24 million glasses of beer. Our lambic is stored in large wooden foeders or stainless steel tanks, each contributing in its own way to the development of complex aromas and flavours. The slow interaction with air and the natural microflora ensures a consistent and authentic taste profile over time.

How a lambic beer reaches maturity

Our fruit lambic beers

Lambic is the base of all our beers at Lindemans Brewery, but the process and ages of the lambic vary.

To create our fruit lambic beers, real fruit is blended with young, one-year-old lambic. This mixture is left to ferment and macerate for at least 24 hours, depending on the type of fruit. Then, it is bottled and pasteurised to stop the fermentation process.

Discover our fruit lambics

Our traditional, sour lambic blends

To produce ‘old’ lambics, like Lindemans Oude Gueuze Cuvée René, we blend both old and young lambic that has matured in oak barrels. Young lambic still contains enough sugars to continue fermentation in the bottle, while the old lambic contributes a dry and sour character, thanks to the remaining yeasts. The in-bottle fermentation means that these traditional sour lambic beers can be stored and cellar-aged just like wine, for up to 10 years and sometimes more.

Over time, the taste of an Oude Gueuze continues to evolve, becoming more refined, complex, and layered as the lambic ages further. This natural transformation is part of what makes lambic beers so unique and cherished by connoisseurs.

Discover our traditional, sour lambic blends

The final step: bottling responsibly

After the finished lambic beer has been meticulously blended or mixed, it is finally ready to be bottled or kegged. Every week, thousands of bottles and kegs are filled automatically in the best conditions in a spotlessly clean environment. Sustainability is important even in this final step. In Belgium, for example, our 25cl bottles can be recycled and reused up to 7 times!