What is a brewing method that produces a sour beer called?

Kettle souring and barrel aging are specific brewing methods employed to intentionally produce sour beers. Kettle souring involves adding lactobacillus or other souring microorganisms directly to the wort before boiling. This process allows the wort to sour quickly, developing sour flavors within a short fermentation time. The wort is then boiled to stop the souring process and further fermented with yeast, leading to a balanced sour beer.

On the other hand, barrel aging allows the beer to mature in wooden barrels that can harbor wild yeast and bacteria, like Brettanomyces and lactobacillus. This method contributes complex sour flavors and aromas over a longer aging period, lending layers of depth to the beer.

While fermentation is a critical aspect of brewing, it does not specifically denote sour beer production. Distillation is a completely different process focused on creating spirits, not beers. De-carbonating does not correlate with the brewing process for sour beers. Thus, kettle souring and barrel aging stand out as the correct techniques for crafting this style of beer.