Kriek is a type of fruited sour beer flavored with cherries. Both the Flemish name, meaning “cherry,” and the beer style come from Belgium. Whereas other varieties are made, traditional kriek is based on spontaneously fermented lambic beer. See lambic. It is a specialty beer from the Senne River valley in the Pajottenland, which is part of Flanders, outside Brussels. Traditionally, the cherries for this brew were a uniquely local type, an extremely sour and tart variety called Schaarbeek, which grew only in a very limited area around the small Pajottenland village of Schaarbeek. Schaarbeek cherries are a relatively small fruit, composed of red pulp and a large pit that ends up adding to the flavors. Nowadays Schaarbeek cherries are grown in other parts of Belgium, mostly in Sint Truinden and Gorsem in Belgian Limburg and in Tienen in Flemish Brabant. A similar variety is also cultivated in other parts of Europe, notably in Poland. To make kriek in the traditional fashion, lambic is aged in oak for 12 to 18 months and then transferred into new casks. There, the cherries are introduced to the matured beer whole, macerated, or crushed, and with the pits intact. The dormant yeast and bacteria in the lambic come back to life and ferment the fruit sugars. The amount of fruit varies but is usually about 20 to 30 kg (44 to 66 lb) of fresh cherries per 1 hl (26.42 gal) of finished beer. The longer the kriek remains in the cask on the fruit—from a few months to a year—the drier it gets and the more bitterness it acquires from the pits. Eventually, the brew is racked off the remaining pulp and mixed with some young Lambic for fresh fermentable sugars. It is then bottled or (rarely) kegged for conditioning and the buildup of effervescence as the yeasts consume the residual sugar from the young lambic fraction. A finished kriek is slightly mouth puckering, refreshing, crisp, and spritzy, with notes of cherry from the fruit, almond from the pits, and complex earthy aromatics from the natural fermentation. It is an ideal beer for sipping out of a Champagne flute on a lazy hot summer afternoon.

Several traditional Belgian krieks are available, with Cantillon Kriek, Cantillon Lou Pepe Kriek, Drie Fonteinen Oude Kriek, De Cam Kriekanlambik, and Boon Oude Kriek enjoying particular respect. There are also many less authentic kriek brands on the market. These tend to be much sweeter than the traditional versions and are often made not with actual sour cherries but with sweetened cherry juice, cherry essence, and syrup added to filtered and pasteurized beers. Although some of these are pleasant diversions with dessert, they are widely derided as ersatz by enthusiasts.

Kriek is usually based upon lambic beer, but some brewers have used other sour beers as platforms for sour cherries. In Belgium there have been versions based upon Flemish red ales and the oud bruin style of brown ale. See belgian red ale. In recent years craft brewers, particularly in the United States, have made many enthusiastically sour and interesting versions of kriek. See sour beer.

Cherries are not the only fruit used for refermenting lambics. The other traditional fruit is the raspberry, and a similar technique is employed. Peaches will yield the less traditional pêche, and black currants produce the darkly colored cassis. Any fruit may find its way into a cask, and brewers have experimented with cranberries, blueberries, and even grapes, with varying degrees of success.

See also framboise and fruit beers.