Oude Geuze Remy Le Mercier

Remy Le Mercier, a 16th-century tax collector from Halle, has been cited repeatedly by historians, past and present, for an ordinance he issued in 1559. The document prescribes the precise proportions of grains to be used in the local beer types “keut” and “houppe.” Brewers who deviated from these proportions were to be fined.
Today, the Halle ordinance is regarded as the oldest known reference to the origin of the lambic beer style — thanks to its specific grain ratios and geographical context.
Unusual by today’s lambic standards, however, is the mention of oats among the ingredients — a grain no longer found in modern lambic breweries. Yet, a composition of 10 % oats alongside at least 60 % barley malt and 30 % unmalted wheat would still meet current legal requirements for lambic.

A precursor of Lambic

Oats, then. That the composition of some beers has evolved throughout history is beyond doubt. Technology has played a role, as has the often underestimated influence of regulation.
But for lambic and oude geuze, the ratios recorded by Le Mercier have remained strikingly similar in percentage terms: roughly 60 % barley, 40 % wheat, and (optionally, not mandatory) oats.
It should be noted that Le Mercier’s ordinance calculated grain proportions by volume (grain measures of 50 litres), whereas modern brewers work by weight (kilograms).

In earlier times, brewers used oats primarily because the oat husks acted as an ideal natural filter in the mash tun — necessary since the first wort was strained through so-called “basket filters.” Oats also lend a sweeter profile to the beer.
However, brewers rarely used more than 10 % oats, since their high fibre (beta-glucan) content tends to increase mash viscosity excessively.

Le Mercier’s ordinance specifically referred to the grain ratios for the beers keut and houppe. The latter can be seen as an early form of today’s lambic — a hopped beer (hence the name) with a mash rich in unmalted wheat, to which hops were added during the boil.

Another, slightly later document by J. B. Vrancken (1825) confirms this, stating that “lambiek was formerly brewed in Brussels, partly with oats or buckwheat as with wheat, one ingredient replacing the other.”

Boon puts it to the test!

Thanks to the meticulous record-keeping of Remy Le Mercier, we know that the origins of the lambic beer style date back at least to the 16th century. More than that — we have taken his description as inspiration for an exclusive Oude Geuze, bottled in a limited run of 5,400 bottles (75 cl) on 22 February 2024. We decided to put history to the test!

Because oats contain more fibre than barley, our lambic took a little longer to clarify, but time did its work beautifully.
With this Oude Geuze Remy Le Mercier, brewed with 10 % oats, we demonstrate that oats can indeed play a meaningful role in the production of Oude Geuze. They lend softness and fullness to the body and help strengthen the foam. The nutty character of the oats is clearly perceptible.

Santé! Proost!

Pouring Ritual for Oude Geuze

You don’t just pour Oude Geuze casually. This is actually the final step in completing the beer, since you (normally) enjoy it from a glass. That’s why it’s so important to do it properly — we all want to experience the beer at its best. Below we explain how to do it in a few simple steps:

1. Open the bottle carefully, and pour in such a way that the sediment remains in the bottle. To make this easier, let the bottle stand upright for a while beforehand so the sediment settles nicely to the bottom.

2. Make sure your glass is clean and dry. Start pouring at a 45° angle and gently rotate the glass as you pour. This motion wets the inside of the glass with beer, helping the foam to build evenly and elegantly.

3. Once the inside is fully moistened, continue pouring slowly and patiently, gradually straightening the glass as it fills.

4. If you’re pouring into multiple glasses, move on to the next one without moving the bottle upright in between. The sediment should not be mixed with the clear beer.

5. Let the foam rise proudly above the rim — don’t scrape it off! The generous, domed head is part of the experience.

6. For the most authentic taste experience, leave the yeast sediment behind in the bottle.