Most people are familiar with ale and lager. These are two of the three branches of the family tree of beer. Less familiar is the third branch – sour beer. For drinkers who expect beer to be bitter, the sour flavour is completely unexpected. I have a secret weapon for imbibers of cider and wine who claim not to like beer. It is a style called Flanders red ale and it is tart, sharp, tangy, tannic and vinous. Serve it in a wine glass and they are none the wiser. When I display the empty bottle they are invariably astonished. They have crossed a flavour bridge and it led them to beer country.
Sour beers are in a renaissance and being brewed by independent brewers across the world. They are no longer niche in Britain because a major mainstream supermarket chain stocks a sour beer brewed in Britain. For centuries the leading brewing nations of purposely soured beers were Belgium with the aforementioned Flanders red ale, and styles known as Gueuze, Faro, Oud Bruin plus fruit beers such as Kriek and Frambozen. In Germany, Gose (containing salt and coriander seeds) and Berliner Weissbier are two ancient types of wheat beer that maintained the sour tradition. Whereas sourness in food and drink often denotes that something is spoiled, in this branch of beer it is the main characteristic.
Sourness is imbued in beer in several ways, all connected with microflora. In some cases the yeast used to ferment the beer is wild – i.e. uncultured – and it lives in the building structure of the brewery waiting to ferment the cereal sugar in the brew. Usually such beers are then aged in old oak barrels which are naturally impregnated with microflora that also feast on sugar. These wild fermentations bestow unpredictable flavours and the requisite sourness. The brewer shows her skills by blending beer from different barrels to create something magical. Another method is to brew ale, and then ferment it with a combination of saccharomyces cerevisiae cultured yeast, and two strains of bacteria, lactobacillus and pediococcus. This is followed by up to two years of aging in oak barrels during which time microflora in the wood also contribute to the sourness. The third method is known as kettle souring where lactobacillus bacteria acidify the wort (the sugary base of the beer) before it is boiled. The fermention is performed by saccharomyces cerevisiae. Fruit such as blackberry, gooseberry, Morello cherry also confers a face-puckering acidity when added to maturing beer.
All these beers impart a refreshing hit to the palate and the sourness has a beneficial side-effect. It acts as an aperitif, stimulates the appetite, prompts the saliva containing digestive enzymes to run, encourages the flow of bile, and enhances efficient liver function. Just what the doctor ordered.
Sour beers are also extraordinarily good with food because their invigorating acidity balances the richness of food and cuts through texture and flavour. Beer already contains tannins from the barley or wheat and sour beers are often aged in oak barrels which also confer tannins that bind with fat and proteins and help to refresh the palate. Hang on, aren’t acidity and tannins the tools that wine and cider employ to match with food? Yes. Another reason for drinkers of those libations to cross that beer bridge and sit down for dinner. A dining table, a feast, a bottle of sour beer and wine glasses to sip it from. Result – a happiness (collective noun) of newly converted beer drinkers. Heaven.