beers are either unfiltered
so the final conditioning of the beer takes place in the bottle, or filtered and then reseeded with yeast so that an additional fermentation
may take place. Not all bottle conditioned beers will referment in the bottle.
Priming is the process by which beer
is wholly or partially fermented in the bottle from which it is served. This is done by adding a small amount of yeast
and sometimes wort
to the bottle before it is sealed. Bottle conditioning is normally done to add carbonation
, and does not usually add much alcohol to the beverage.
Bottle conditioned beers are usually carbonated entirely by the natural action of the yeast, as opposed to filtered beers which are carbonated using high pressure gas injection.
Filtered beer tends to have a relatively short shelf life
, rarely more than a year, as many compounds in the sterile beverage break down into unpleasant tasting ones. Live yeast inside the bottle acts against these processes, giving the beverage a much longer shelf life. A good bottle conditioned beer can maintain its drinkability for many years, and some can be aged for decades.
Bottle conditioned beers vary in clarity. If the yeast remains in suspension, the drink can appear murky or even chunky. But if the yeast is dense and settles, the drink can be completely transparent with only a thin yeast layer at the bottom. The yeast solids are usually referred to as the sediment or dregs, especially once opened.
Serving such a beverage involves either decanting
the drink into the serving glass, leaving the sediment behind in the bottle, or pouring all the contents into the glass, including sediment, to be drunk together. This is generally a matter of personal preference, though sometimes the brewer will suggest a preferred method for a particular beer. Yeast sediment has an earthy flavor and is rich in B vitamins. Drinking the sediment has some nutritional benefits, but it does slightly change the flavor and mouthfeel of the beer. In some beer cultures, it's common to pour the sediment into its own shot glass
to be drunk separately.
Kräusening is adding active wort
or other sugar nutrients to beer that is being bottled. The name is German in origin, though the method is used by brewers in various countries - most notably Belgium. Kräusening encourages the yeast to continue fermentation in the bottle. It helps clean up the flavor of the beer by reducing levels of diacetyl