Sour beer and gueuze: lambic, kriek and Flemish red

Lambic is a wheat beer that ferments spontaneously. The boiled wort cools in the open air and takes up wild yeasts and bacteria from the surroundings. No yeast is therefore added. According to the Flemish inventory of intangible heritage, lambic comes from the Zenne Valley, the Pajottenland and Brussels, and is brewed only from early October to the end of April, because the cold helps the micro-organisms.

After brewing, lambic matures for at least a year in oak casks. The BJCP, the international organisation for beer judges, names unmalted wheat and pilsner malt as the base, and hops that are three years old or more. That old hop serves mainly as a preservative, not for bitterness. Pure lambic is traditionally served without carbonation.

Geuze is a blend of lambics of different ages that undergoes a second fermentation in the bottle. According to the BJCP, lambics that are one, two and three years old are blended and then cellared. As a result, geuze is highly carbonated, whereas lambic is served flat. That blending can also take place outside the brewery, at a blender that does not brew itself.

European rules apply to Oude Geuze. The name is a Traditional Speciality Guaranteed, notified by Belgium and registered in 2017 with a reservation on the name. The specification requires spontaneous fermentation, a weighted average age of at least one year, an oldest lambic that matured for at least three years in wooden casks, and a secondary fermentation in the bottle on the lees.

Kriek is lambic in which sour cherries have matured. The BJCP names cherries and raspberries as traditional fruits. In the past, the blender or the pub landlord added the fruit to be able to serve more kinds of beer. Modern versions also use peach, apricot or grapes.

On the label, the word Oude makes a difference. Oude Kriek, Oude Kriekenlambiek and Oude Frambozenlambiek are also protected. According to the European specification, cherries, cherry juice or concentrate must make up 10 to 25 percent of the weight of the end product, and the mixture ferments again in the bottle. Many fruit beers without that mention are, according to the BJCP, sweetened afterwards, with natural or artificial sweetener.

Flanders red and oud bruin are sour beers from Flanders that do not ferment spontaneously, but gain their acidity during long maturation. The BJCP places Flanders red in West Flanders and links the style to Rodenbach in Roeselare. There the beer matures for up to two years in large oak foeders, almost 300 of them according to the Oxford Companion to Beer. Rodenbach Classic is a blend of young beer and aged beer.

Oud bruin comes from East Flanders and, according to the BJCP, is associated with the Liefmans brewery. It is darker and maltier than Flemish red, and less vinegary. For Flemish red the BJCP gives 4.6 to 6.5 percent alcohol, for oud bruin 4 to 8 percent.

A fruited sour is a modern sour beer with lots of fruit, usually soured quickly rather than aged on wood for years. Many of these beers are made with kettle souring. According to CAMRA, the British beer consumers' organisation, the brewer adds lactic acid bacteria (lactobacillus) to the wort before boiling. Once the desired acidity is reached, boiling kills the bacteria.

That is a fast method that gives the brewer a lot of control over how sour the beer becomes. The difference from lambic therefore lies in the method: no wild fermentation from the air and no years in oak, but targeted souring in the brew kettle. Dutch brewers such as Jopen also make fruited sours.

In de winkel staan nu 19 flessen zuur bier, het grootste deel uit België en de rest uit Nederland. Voor geuze zijn er de Oude Geuze Boon, de Boon Geuze Mariage Parfait en de Brouwerij Boon Oude Geuze Megablend 2022. Fruitbier is er van onder meer Bacchus Kriek, Bacchus Frambozenbier en Lindemans Cassis Fruitbier.

Also on the shelf are Rodenbach Classic, Duchesse de Bourgogne and Liefmans Goudenband, along with De Wilde Brouwers The Wild Specials Flemish Red Ale and Sour Cydonia. Modern fruited sours come from Jopen, such as Sour N' Sweet and No Sleep Till Haarlem with Sleeping Village Brewing. Liefmans Fruitesse On The Rocks 0.0% is alcohol-free. Would you like advice? Feel free to call or drop by ’t Bockje at Brink 2 in Bathmen.

The shop is at Brink 2 in Bathmen. Open Tuesday to Friday from 09.00 to 18.00 and Saturday from 09.00 to 17.00. For advice, call 0570 541 278 or email info@bockje.nl.