As the name implies, wild fermented beer is brewed using wild yeast or other microorganisms in nature. This brewing method is different from traditional pure yeast fermentation. It introduces more types of microorganisms, giving the beer a more complex and multi-layered flavor. Recall that the wild beers we have drunk seem to be sour - but is wild beer necessarily sour?
Wild beer is beer fermented with wild yeast. Wild yeast is defined by its source, that is, from the natural environment inside or around the brewery. Brett yeast is the most common wild yeast, but the sour taste in wild beer is not brought by these wild yeasts (fungi), but by bacteria such as lactic acid bacteria and pediococcus (producing lactic acid) and acetobacter (producing acetic acid). 'Therefore, the "wild" taste produced by wild yeast is not necessarily related to the sour taste produced by these bacteria.
The birthplace of wild beer is the Senn Valley in the Brussels area of Belgium. Because in the history of brewing wild beer (such as Lambic and Flanders Red Ale), the flora in the natural environment of the Seine River happened to contain wild bacteria, mainly Brett yeast, and acid-producing bacteria, which led to the fact that the wild beer brewed at that time was indeed sour. This was originally a wonderful coincidence, but over time it also shaped a fixed aesthetic that complemented the "wild" taste of Brett yeast with lactic acid and acetic acid produced by bacterial metabolism, so that when wild beer went out of Belgium and began to be reproduced and developed in countries such as the United States, brewers would still intentionally (out of aesthetic preference) or unintentionally (due to technical limitations) brew sour wild beer.
Now, due to technological advances, we can analyze the flora from traditionally well-known wild breweries and extract specific microorganisms, such as Brett and other types of wild yeast. Some breweries (such as Wild Goose) began to try to add only wild yeast without acid-producing bacteria, and the fermented flavors are usually dominated by fruits (such as pineapple, apricot) and floral aromas. Shangri-La Craft Brewing uses completely natural fermentation to brew wild beer that is full of gamey flavor but not sour, proving once again with actual examples that wild beer is not necessarily sour.
