Wild ale or sour ale: the difference and why it matters
Wild and sour often get used as if they mean the same thing. One describes how a beer was fermented. The other describes how it tastes. Keeping them apart helps you choose. It also explains why some of these beers cost so much more than others.
Two different questions
Sour describes flavour. A sour beer is noticeably tart, from acids produced by bacteria, mostly lactic acid and sometimes acetic acid. Wild describes fermentation. A wild ale is fermented, at least partly, by microbes other than ordinary brewer's yeast: wild yeasts like Brettanomyces and bacteria such as Lactobacillus and Pediococcus, sometimes caught from the air.
The two overlap a lot, which is why the terms get mixed up. But you can have a sour beer that was not wild. You can also have a wild beer that is not especially sour.
Sour without being wild
Many sour beers today are made by kettle souring. The brewer makes wort, cools it to around 35 to 45 °C and adds a pure culture of Lactobacillus. Over a day or two the bacteria produce lactic acid and the pH drops. The brewer then boils the wort, which kills the bacteria. Normal brewer's yeast then ferments it.
The result is clean and tart, often with fruit added: a Berliner weisse, a gose or a fruited sour. It is controlled, quick and predictable. Nothing wild happened. Our guide to sour beer for beginners covers these styles if you are just starting.
Wild without being very sour
Brettanomyces, often shortened to Brett, is a yeast that brewers once treated only as a spoiler. In some beers it is now welcome. It works slowly over months, eating sugars that brewer's yeast leaves behind and producing earthy, funky and fruity aromas: hay, leather, pineapple, clove, sometimes a barnyard note.
Brett makes some acid, but not much. A beer fermented with Brett alone can be very dry and funky while only mildly tart. Many farmhouse ales and some Belgian beers fall into this group.
Both wild and sour
The classic beers in this group are made by spontaneous or mixed fermentation. Belgian lambic is the famous example. Brewers in the Senne valley near Brussels cool hot wort overnight in a wide, shallow vessel called a coolship, open to the air. Wild microbes settle in and the wort ferments in wooden barrels for one to three years.
Over that time a sequence of microbes takes turns: wild yeasts, then lactic bacteria, then Brett. The finished beer is sour, dry and deeply complex. Flanders red and oud bruin are other traditional examples, often aged in large oak vats.
What you taste in each
A rough guide when you have a glass in front of you:
- Kettle sour. Clean, bright tartness like lemon or yoghurt. Often fruity. Little funk. Usually fresh and light.
- Brett beer. Earthy, funky, tropical or leathery. Dry. Mildly tart at most.
- Mixed or spontaneous fermentation. Layered sourness with funk, oak, dried fruit and a long dry finish. Often more complex the older it gets.
Smell for funk before you taste for acid. If you find hay or leather, Brett was probably involved, whatever the label says.
Why the difference matters
Time and risk explain the price gap. A kettle sour can be ready in two or three weeks. A traditional lambic or barrel-aged wild ale takes a year or more, ties up barrels and space and carries the risk that a batch goes wrong and has to be dumped. That cost shows up on the bill.
It also matters inside a brewery. Wild microbes can spread to clean beers through hoses, gaskets and wood, so breweries that make wild ales often keep separate equipment. An unplanned sourness in a lager is an infection, not a style. Learning to taste the difference between intended character and a fault is one of the most useful skills a drinker or a brewer can build.
Trying them in India
Several Indian craft breweries make kettle sours, often with local fruit such as jamun, kokum or passion fruit. True wild and barrel-aged beers are rarer here, partly because heat and humidity make long ageing tricky and partly because of the equipment they need. Imported bottles turn up in some cities.
Serve sour and wild beers at about 8 to 12 °C in a tulip or wine glass. Pour small measures and share. These are beers for slow sipping and conversation, not for thirst.
Common questions
Is every sour beer a wild ale?
No. Kettle sours are soured with a pure culture of Lactobacillus and then fermented with ordinary brewer's yeast, so they are sour without being wild.
Does Brettanomyces make beer sour?
Only a little. Brett mainly adds funky, earthy and fruity aromas and dries the beer out. Strong sourness usually comes from bacteria.
Why are wild ales so expensive?
They often take a year or more to make, tie up barrels and space and risk losing batches. Kettle sours are quicker and cheaper to produce.
Is a sour taste in a lager a fault?
Yes. In a style that should be clean, sourness usually means a bacterial infection rather than intent.
