Note: in the current (2015) BJCP Style Guidelines, Baltic Porter is style 9C. Category 9 Strong European Beer, contains more strongly flavored and higher alcohol lagers from Germany and the Baltic region. Most are dark, but some pale versions are known.
These beers are dark, malty cold-lagered beers, usually about 10% ABV, stronger than a robust porter. Because it is an "imperial porter", it's alcohol level is high and it may show some complex alcohol notes along with some alcohol warmth. It may also have some lager fruitiness such as berries, grapes and plums. Banana or other ale-like fruity esters from warm-temperature fermentation are not appropriate in this beer. This style has the malt flavors of a brown porter and the roast of a schwarzbier, but it has more alcohol and body. Occasionally, these higher alcohol, sweet robust porters will exhibit a vinous Port-like quality. Overall, this is a complex beer with multi-layered flavors.
The beer started out being brewed as an ale when Britain began exporting porters to the Baltic area. To make sure the beer arrived in good shape, the English brewers brewed the beer with more alcohol and hops. Thus this style is to porters as a Russian Imperial Stout is to stouts. The beer's dark brown color masked the cloudiness and the smoked highly kilned brown malts of the time also masked other brewing problems. There was also a portion of stale ale added which imparted a pleasant acidic character to the beers and which helped make Baltic Porters quite popular.
Brewers from countries neighboring the Baltic Sea became inspired by all the money England was making. They began brewing their own versions. These beers are still being brewed in countries bordering the Baltic coastline and include Finland, Estonia, Latvia, Lithuania, Poland, Russia, Denmark and Sweden. Although it was introduced as an ale, during the second half of the 19th century, the breweries around the Baltic began making the beer as a lager, with bottom-fermenting yeast. Very few top-fermented examples remain today.
Some important factors to remember when brewing a Baltic Porter recipe include getting the dark fruits and rich flavor without the accompanying acrid and burnt notes, and keeping the ester profile low with an appropriate yeast or fermentation profile. To keep the bitterness down, use a de-bittered black malt such as Carafa Special from Weyermann. This will give you a touch of roastiness, but none of the bitterness usually associated with the husks in roasted barley or black barley. Some residual sweetness will also help smooth out the harsh flavors of the darker malts. Use a German lager yeast for their clean profile, but if you must use an ale yeast, find a clean American ale yeast and ferment as cool as possible. The bittering hops are mostly from Hallertau, such as Tradition or Mittelfruh. Many Baltic brewers add small amounts of Czech Saaz or Polish Lublin as aroma hops. Some even add some licorice to the boil to increase the licorice aroma and fullness in their beers.
References: Information for this page was adapted in part from the Wikipedia article entitled Porter (beer), Brewing Classic Styles 80 Winning Recipes Anyone Can Brew, written by Jamil Zainasheff and John J. Palmer, the Beeradvocate.com article entitled Baltic Porter, the article Introducing The Baltic Porter written by Jens Eiken from The Jacobsen Brewhouse in Carlsberg, Denmark and published in the Scandinavian Brewers' Review Vol. 64 No. 5 in 2007, and the 2008 BJCP Style Guidelines.
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