The last step in the beer brewing process, after extracting sugar from grain, boiling the wort and fermentation, is adding carbonation. Carbonation not only makes the beer easier to drink, but also adds to the aroma and flavor. Without carbonation, beer is not really beer.
Brewers use two methods to carbonate beer. In natural carbonation, the brewer allows yeast to remain in the fermented beer and adds sugar. The yeast consumes the new sugar and ferments again, releasing carbon dioxide. This process is also known as refermentation.
Forced carbonation, as the name implies, directly pushes carbon dioxide into the beer. The brewer places the beer inside a sealed container, where a machine rapidly adds the carbonation under high pressures. This is a high-speed option that turns out a finished product very quickly.
Besides the difference in speed, the two carbonation methods bring out very different flavors. Naturally carbonated beer retains some of the biting flavor of the yeast, making the taste somewhat bready. Brewers who use natural carbonation swear by the complexity that the yeast brings to the overall flavor. Those who do not like the taste should opt for forced carbonation.
Beers made with these two methods also differ in appearance. Force carbonated beer has no sediment at the bottom of the barrel, and the liquid appears clear when poured. Bubbles stick to the inside of the glass. Natural carbonation, in contrast, leaves a thin layer of yeast at the bottom. The head is thick, foamy and has plenty of peaks and valleys. Fewer bubbles stick to the inside of the glass.
When drunk, naturally carbonated beer feels smooth in the mouth, almost resembling a champagne. In contrast, the texture of force carbonated beer resembles nothing so much as commercial beer. That is no coincidence, as most commercial breweries use forced carbonation.
One of the biggest downsides of forced carbonation is that it requires fairly expensive equipment. This isn’t an issue for commercial breweries, but many home brewers prefer to spend their money on ingredients rather than kegging equipment for forced carbonation. Natural carbonation is fairly inexpensive, since it uses yeast left over from the fermentation process. The only added expense is the sugar needed to encourage the yeast to ferment again.
Ultimately, the choice between natural and forced carbonation comes down to personal preference. Home brewers who like the appearance, texture and taste of their naturally fermented beer need not invest in expensive equipment to try forced carbonation. On the other hand, brewers who prefer the taste of commercial beer should consider trying forced carbonation to better fit their palates. The key is to carbonate the beer well, regardless of the method, to give the beverage a great texture, aroma and taste.