Dark Beer Isn't Actually Always Stronger Than Light Beer. Here's What To Know

One of many myths about beer is the assumption that dark beer has a higher alcohol content than light beer. The process that produces dark beer, such as stouts and porters, does contribute to some notable differences, in particular the beer's flavor and color. During the brewing process, dark beers are made using roasted malts at higher temperatures, which gives them a comparatively richer flavor and color than golden, crisper light beers such as pale ales or lagers. Nevertheless, there is actually no correlation between dark beer and higher alcohol content. To find out why, Food Republic spoke with Brian Kulbacki, owner and head brewer of Departed Soles Brewing Company in Jersey City, New Jersey.

"A beer's alcohol content is determined by the difference between the sugar content of the wort prior to fermentation, and the remaining sugar after fermentation," Kulbacki explained. Wort is the liquid extracted during the mashing process in beer brewing and contains the essential sugars which are fermented by the brewing yeast and turned into alcohol. While dark beer uses roasted malt, this doesn't mean it has more sugar, and the alcohol content of dark and light beer depends on the overall recipe — not the malt color — so they can have similar or different alcohol levels. "Porters, brown ales, and milds are all popular 'dark beers' that are often just as light in body and low in alcohol content as pale ales and non-light lagers," Kulbacki told us.

To create a beer with a high alcohol content, the formula is simple: increase the amount of fermentable sugars by adding more malted grains or cereals into the mash, or add in extra brewing sugars like dextrose or sucrose, which are easily converted into alcohol. Sometimes, the type of yeast you use can be more alcohol-tolerant than other yeasts. Simply using roasted malts has no impact on the alcohol, and can actually reduce the alcohol potential of the beer. 

"Roasting a malt reduces the available sugars in the mash process," Brian Kulbacki explained. "The Maillard reaction that occurs during floor/drum roasting caramelizes many of the sugars within the malt, thus reducing the original sugar content of the wort prior to fermentation, while creating the flavors that those malts are known to produce." This means there are fewer sugars available to be turned into alcohol and carbon dioxide.

Kulbacki also noted that there are numerous examples of light-colored beers that are surprisingly strong when compared to milder dark beers, particularly within the craft beer category. These include styles such as double or triple India pale ales and Belgian tripels. He pointed out the contrast: "While there is a popularity for 'imperial' stouts, the most popular one in the world — Guinness — is only 4.2% alcohol by volume." Ultimately, a more reliable indicator of a beer's alcohol content comes down to the specific brand and its brewing practices, rather than the beer's color.