Bottled beer has been around since the 1500s. Before that, the only real way to get your beer was straight from the barrel. Now, the most common way for you or I to have a beer at home is for us to buy a six-pack. So, how is beer bottled? What gives it the carbonation? Why are some beers more carbonated than others?
There are two major ways for a bottle of beer to have carbonation in it. The first, and original, way for beer to be carbonated was the beer was to be sealed in bottles before the fermentation was finished. When fermentation occurs, it releases CO2. Airlocks in fermentation tanks release this CO2.If the tank is sealed, the CO2 has nowhere to go, and therefore stays in the liquid. Since bottles are airtight, the it continues to ferment, carbonating the bottle of beer.
However, this is more difficult to do than it sounds, since bottling the beer too early in the fermenting process could easily result in the bottles becoming too carbonated, and burst the bottle. This resulted in a modified method of bottling beers. The modern method is to ‘prime’ the bottles. In non-filtered beers, yeast is still present in the bottles. Therefore, just before bottling, priming sugar mixed with water is added to the fermented beer. This allows for a more controlled amount of sugar to be present in the bottle before it’s fermented inside the bottle.
In modern mass-produced beers, bottling is very different. Since most mass-produced beer is filtered, and therefore, lacks yeast to ferment inside the bottle, the carbonation is more directly added. The bottling company simple adds CO2 inside the bottles and the gas enters the liquid.
Some beers, notably Guinness, and other similar beers, like Tetley’s, use Nitrogen for most of their pressurization. The nitrogen is less soluble than the CO2. This means that the beer can be pressurized higher with less ‘fizzyness’. This is why, when you drink it, nitrogenated beers taste so smooth. The bubbles of nitrogen form very small bubbles compared to CO2, leading to a creamy head.