I had my first nitro beer (BJ’s PM Porter) last night at BJ’s Restaurant & Brewhouse. (This is a topic for another time, but they are handling COVID-19 the right way in Fresno, with their spacious outdoor dining.) The PM Porter had dark, roasted grains that lend a unique coffee presence, with a slight sweetness reminiscent of molasses. The nitro process further compounded how sweet and creamy Porters usually are.
Nitro refers to the nitrogenation (the nitrogen equivalent of carbonation) of beer. Why do this? Nitrogen is rather inert and not very soluble in beer, which means it doesn’t affect taste as much and is minimally bubbly. CO2 on the otherhand, is actually acidic (its why sodas aren’t the same when they’re flat), and is more percieved so with their sharp bubbles. Nitro can give the right kind of beer a more pronounced creamy and smooth texture. The beers that would benefit most from the nitro process will be Stouts and Porters. These beers are dark, creamy, rich, and malty. Their grains tend to contribute a bitter dark chocolate flavor to them, with a hint of sweetness.