Two methods of fermentation
You may recall, we started this two-parter with the first stages of the brewing process. The three basic methods of beer fermentation are: in a warm environment; a cool environment; or via wild or spontaneous means. The method used generally results in the following categorisation of beers: ale or beer; lager; and lambic or sour beers.
Let’s take the last, and possibly the most interesting method first, spontaneous fermentation. With this method the brewer doesn’t add any cultivated yeast to the wort, but lets the natural yeasts found in the air or container, work their magic on the liquid. Lambic beers are among the best known spontaneously fermented beers, only coming from the Pajottenland region of Belgium.
Warm fermentation is where cultivated yeast is added to the wort, and the temperature is usually kept between 15-20°C. Once the fermentation has begun, this first phase can be over in 2 to 6 days. Cold fermentation is where the wort is cooled to around 10°C, which gives a slightly slower rate of fermentation, and a slightly higher rate of CO2 absorption. Fermentation time is also longer, anywhere between 4 to 10 days for the first phase.
The secondary phase of fermentation can also be called conditioning, or maturing/aging the beer. This is where the majority of the yeast has converted the freely available sugars to alcohol, and it now needs to start working on the harder to convert sugars. Most warm fermented beers, (traditional ales) can take 2 to 3 weeks for this conditioning to complete, before it’s ready to be fined, or filtered, and packaged. Cold fermented beers, (lagers), are where they’re stored at a cellar temperature (8-10°C) for a period of time. The point of conditioning the beer is to let the yeast get to work on some of the more undesirable flavour characteristics by removing them from the brew, and towards the end of the process, let the yeast flocculate (settle) out and clear the beer.
When the beers have finished their conditioning, the brewer then has to decide what format the beers will be delivered to the drinker, be it cask, keg/keykeg, bottle or can. For real ale, the preferred container is either the cask or bottle. The cask comes in a number of sizes, ranging from a pin (4.5 gallons) to a tun (216 gallons). The most common sizes are firkins, (9 gallons) and kilderkins (18 gallons). It is then tapped, vented and served directly via gravity or from a beer engine (hand pull). Kegged beer is where it’s served via a separate chiller using gas to push the beer through the pipes.
That’s it for now, so until next time, we’ll see you at the bar!
Rich - The Beer Emporium