The bitter wort must be chilled to a yeast-friendly temperature as quickly as possible, in order for fermentation to commence. (Too hot, and the yeast is killed. Too cool, and the yeast lies dormant.) This is a step that varies drastically from beginner to mega-brewing pro. The simplest method is to immerse the kettle in a basin of ice water. A step up from that involves a coil of copper known as an immersion chiller, through which cold water is run while it is submerged in the wort. More complicated and effective is the counter-flow wort chiller that is employed by homebrewers on up. Hot wort runs through an inner tube while cold water (or glycol) runs in the opposite direction. The heat exchange is thorough from inlet to outlet. During cooling, more unwanted proteins (known as “cold break”) are precipitated out of the wort.
Fermentation, whether it takes place in a plastic bucket, glass carboy, or conical stainless steel tank, is the work of Saccharomyces cereviseae or uvarum, more commonly known as brewing yeast. Beyond simple metabolic conversion of maltose to carbon dioxide and alcohol, its role in the character of a brew is as important as malt, hops, and water. The “footprint” of various yeast strains are manifested in the various styles. Lager yeasts work at cool temperatures, ale yeasts at more elevated temperatures. The complexity of a Belgian tripel or the smoothness of a German doppelbock owe their character to these workhorses. Classic strains (including English) have been selected over centuries of brewing to give beers a unique signature. Beginners ferment at ambient temperatures, whereas pro brewers use glycol-chilled fermenters of different volumes to control their ferment.
The manner in which the beer is handled post-fermentation is a critical prelude to packaging. The degree to which it is refined is greatly determined by the level of brewing. Homebrewers seldom filter, instead relying on natural sedimentation. Storage in a secondary (or tertiary) vessel settles the larger particles. Cold conditions help precipitate them even further. Brewpubs and small brewers use large conditioning tanks and cold temperatures to do the same as homebrewers and they may or may not use subsequent filtration downstream. True filtration is seldom performed by homebrewers, sometimes carried out by medium-size operations, and almost always done by large breweries. True filtration comes at a cost, as some of the components are removed along with the unwanted particles, giving the finished brew a thinner texture.
Packaging beer, at any production level, is a matter of feasibility. Homebrewers have the option of bottling, the bane (or kegging) the godsend. The truth is, that as tedious as bottling is, it has its advantages in portability, and offers bottle-conditioning. Kegging is simple and offers the pleasures of draft beer, but requires dedicated refrigeration and extra equipment. Brewpubs seldom bottle—after all, the point is on-premise enjoyment— and rely on convenient serving tanks and (increasingly) micro-kegging operations rather than bottles. Homebrewers and brewpubs also have the option of popular growlers to go, but their life is fleeting. Regional and macrobrewers usually have the resources to offer bottles, kegs and cans. The cost and maintenance is immense and the machinery is something to behold. Generally, the beer is so refined at that point anyhow that it makes little difference the vehicle, as long as the bottling is done with care.