Brewhouse Souring

Posted September 3, 2015

Category: Technology

As beer styles featuring acidity or tartness continue to grow in popularity, it has become important to educate beer drinkers on the intent and process involved in producing specific styles that have been lumped together based on their pH. While acidity is certainly a common factor, it alone does not necessarily mean that it’s possible to accurately or reasonably compare a sour saison to a gose to a Flanders-style red. These are three very different styles with acidity that may come from employing various yeasts, bacteria, processes and equipment.

For our newest year-round Smokestack Series beer, Tell-Tale Tart, we use a process commonly referred to as brewhouse or kettle souring. We mash and lauter as we would for a normal beer, but the process takes a slight turn before boiling occurs. Using our brewhouse heat exchanger, we lower the temperature of the wort to 100 F and transfer it to our wort kettle that’s been purged with carbon dioxide. We perform the CO2 purge to ensure that the only acid producing bacteria that’s active is lactobacillus, the same bacteria that’s responsible for making yogurt or sauerkraut sour. Over the course of the next 48 hours, lactobacillus goes to work consuming fermentable sugars created during mashing and producing lactic acid. Once the pH of the wort has dropped to our target acidity, typically around a pH of 3.4, we boil the wort and proceed as if we were brewing a normal beer. Since the acidification occurs before boiling, we’re able to create a tart/acidic beer without running the risk of infecting our fermentation vessels with acid producing bacteria.

As the lactobacillus is killed during the boil, beers that are brewhouse soured will not continue to develop increased acidity in the bottle or keg after packaging.

- Jeremy Danner, Ambassador Brewer