In the Beginning...
Making beer starts in the field where hardworking farmers raise acres of barley and wonderful hop bines. Barley is grown in winter and spring varieties, and barley for beer is grown in 2-row and 6-row varieties. Hop vines are an annual crop, harvested flower buds, or cones, being the fruit of the plant brewers have interest in. The vines may be trimmed back, and the core of the plant left in the ground for next year. Barley grain is then sent to the maltster, and hops are either immediately used, frozen and vacuum packed until use, or compressed into pellets and stored for future use.
Harvested grain is allowed to germinate for 1-3 days until the desired level of modification is achieved. Then the grain is dried using heat to varying degrees and drying times to produce the varying types and styles of malt. For some styles of malt, additional preparations are preformed such as smoking or roasting. The malted grain is milled using varied designs of grinders that attempt to break up the starch rich "meat" of the grain, while leaving the hulls as intact as possible.
Mashing and Lautering
The starches are broken down to fermentable sugars and extracted into water from the milled malt grains or grist by processes called the mash and the lauter. The mash uses heat at specific temperatures to activate certain enzymes that break starch chains down to sugars that can easily be consumed by yeast. Lautering is simply the straining of the spent grain from the sugar enriched water. Sparging is another process that rinses the spent grain, and is usually done as a part of the lautering.
There are three major fashions in which the mash is preformed; Infusion, Temperature Controlled Step, and Decoction. The infusion mash is the simplest, in which grist and water are combined and held at a single temperature until the conversion of starches to sugars is complete. It gets its name from the "infusion" of hot water into the grist to obtain the initial temperature. The step mash gets its name from the manner by which the temperature of the mash is brought to an initial point, held there for a period of time, called a rest, and then raised to another rest, and sometimes again. If you plot the temperature with respect to time, the plot will appear to be "steps." The Decoction mash is the oldest method and is done by infusing boiling water to the mash to achieve initial temperature rest. Sometime before the end of the rest, a measured amount of the mash (water and grist) is removed and brought to a boil. When added back in, the mash temperature raises to the next rest. This is usually done once more, and sometimes a fourth rest is used.
The Lauter and Sparge
Once the starches are converted to sugars, and dissolved into the mash water, the sweet liquid is drained away and sent to the boil. The sweet liquid can be filtered through a collander or a screen, but it is often more desirable to carefully drain the liquid away from the grain to avoid excessive aeration of the hot liquid, since this will cause oxidation. Usually the lauter and the sparge are done as one operation.
The mash is carefully put into a lauter tun, using some sparge water to keep the surface of the liquid above that of the grain. This allows the grain to form a "bed" where the spent hulls support each other and form a filtration structure, while the higher temperature of the sparge water stops further enzymatic activity. Sometimes the mash tun and the lauter tun are one and the same, in which case sparge water is added to the mash to maintain the surface while part of the mash is drained and cycled back into the mash. Once the mash is completely transferred, or the cycling liquid "runs clear," or has no large particles, the sweet liquid is slowly drained to the boil kettle while fresh sparge water is carefully added to the top of the tun. When the volume of liquid from the mash is drained, lautering is considered complete. But, the process is usually continued, and is called sparging. The resulting liquid can now be called wort.
The sweet liquid that results from the mash, lauter, and sparge can be considered "extract." The all-grain home brewer ignores this and proceeds to the boil. However, this liquid can be concentrated, by boiling down to a thick syrup, or cooked into a dry powder. These are the forms we usually refer to as "malt extract." Bulk malt extract and unhopped extract kits are produced this way, and pre-hopped extracts are either obtained after the boil or simply mixed with hop extract.
When a brewer uses malt extracts to make beer, he must first "unconcentrate" the extract. This can be compared to making orange juice from frozen orange juice concentrate. An amount of water is brought to a boil, then removed from the heat source. The malt extract is stirred in, dissolving into the liquid, which then can be again called wort.
Hops are then added to the wort, and boiled therein for an hour or more. This causes alpha acids in the hops to break down and dissolve into the wort. Some adjuncts that could not be added in the mash can also be added to the boil, as in the case of molasses, or if a mash was not performed at all (this is then called partial mash brewing). Near the end of the boil more hops may be added to impart flavors and aromas from the hops, certain fining agents may be added such as Irish moss, and certain other adjuncts may be added to pasturize them while leaving their starch chains intact.
Before pitching yeast, the wort must be cooled to a yeast friendly temperature. This can be done by immersing the brew kettle in a tub full of cold water, placing a special chilling coil into the wort, or special chillers that the wort actually passes through. Quick cooling lessens the potential for early bacterial contamination or oxidation of the wort. Slow wort cooling can allow dimethyl sulfide to build up in the wort, which will produce off flavors. Rapid cooling also aids in cold break formation, allowing a clearer beer to be produced.
Professional and commercial breweries usually maintain a culture of yeast that they use in their beer. Many homebrewers do the same, and the science, or art as some might consider it, of maintaining a yeast culture is called zymurgy or, more affectionately, yeast farming. This process can be considered apart from the brewing process, since viable yeast cultures can be bought and quickly pitched to a cooled wort, but a wise brewer knows that understanding how yeast lives is very important to understanding how yeast makes beer. In fact, most experienced homebrewers will prepare what is called a "starter" to pitch instead of blindly tossing in the contents of the store bought vial.
A nurturing environment is produced that is rich in sugars and nutrients, into which yeast is pitched. The mixture is allowed to ferment for a day or two, or even a few hours, after which the sediment may be harvested and placed into cold storage. The yeast sediment may also be freeze-dried to produce the dried yeast that comes in packets with many shelf stored beer kits. The stored yeast, in liquid form, can be expected to have viable cells several months later, but a yeast farmer will repitch after no more than a month, both to keep the culture alive, and to revitalize the amount of viable cells.
A day or two before brew day, a smart brewer will create a starter by preparing perhaps a quart of wort, using a DME (dry malt extract) for simplicity and then pitching either a sample from his yeast farm, a store bought vial of liquid yeast, or rehydrated dry yeast. The yeast will multiply in number until they reach an optimal threshold of yeast per volume of wort, and the fermenting starter will exhibit signs of primary fermentation and it is then ready to pitch to the wort. As an aside, professional breweries who ferment in large batches might make several starters, i.e., a quart to start a five gallon starter to start a 60 gallon barrel. By doing this, the brewer shortens the time it takes for primary fermentation to start, and thus minimizes the chances for unwanted microbials getting a foot hold and ruining the batch.
Fermentation is said to have two stages; primary and secondary. In primary fermentation, yeast is very active, reproducing itself and consuming the easily converted sugars. The process may seem violent, and a foam head will form, which is called krauesen. Once the krauesen "drops," or settles to the bottom, primary fermentation is complete and some brewers will transfer the fermenting liquid off of the sediment and into a secondary fermenter. This is done to prevent the spent yeast cells from negatively affecting the flavor of the beer, however the benefit of doing this is somewhat debatable, and some brewers choose not to do this.
Fermentation can take a couple weeks to a month, or even longer depending on the amount of sugars in the wort and the difficulty of conversion. Light body beers can be quickly fermented with fast working ale yeast. Conversely, heavy body beers fermented with colder working lager yeast can ferment a lot longer. Primary fermentation usually is complete within the first week.
Before consumption beer is normally carbonated, and often aged for a week or more. Generally, longer aging produces a better beer, but too much aging can negatively affect the quality. Beer can be naturally or artificially carbonated. Natural carbonation capitalizes on the fact that even after fermentation is complete, yeast remains suspended in the beer. After transferring the beer into an intermediate "bottling" or "priming" bucket, additional fermentable sugar is added to the beer. The beer is allowed to sit for up to 24 hours, in which time the suspended yeast reawakens and begins to convert the new sugars. The beer is then put into a sealed container or containers, such as a keg or recappable bottles. Within a week the yeast will have converted the new sugars into a negligible amount of alcohol and an amount of CO2 adequate to pressurize the container and carbonate the beer.
Aging becomes most important when the sugars added are different than the sugars present in the source wort. Priming corn sugar is quickly converted and so will result in larger bubbles and a thin head. Given time under pressure these bubbles will break down and allow better head development. Priming malt will perform better, but both priming sources will introduce flavors that may not have been present in the original beer. A process called krauesening is optimal, but requires slightly more work. Aging also allows the suspended yeast to settle, and allow the beer to clear, resulting in a cleaner looking and tasting beer.
Artificial carbonation is done by putting the beer into a keg and applying pressure from a CO2 tank for at least 24 hours to force carbonate.
Artificially carbonated beer should be poured into a stein, to avoid sloshing the sediment while drinking. Steins should be washed using a diluted bleach solution, since dish soaps will leave a film on the glass that will destroy beer head. Homebrewed beer still has suspended yeast cells in it, which is a Good Thing(TM). When a human drinks alcohol, its body uses vitamin B complex and water to neutralize and rid itself of the alcohol. If it didn't do this, the human would remain perpetually drunk, which might sound good, but then the human would be unable to drink more beer since it would probably kill it. Now, when that human wakes in the morning after two cases of beer, a bottle of BaerenJaeger, and a few hours praying to a porcelain god, the human's body is depleted of vitamin b and is dehydrated from excessive gifts to the aforementioned god. Yeast cell walls contain vitamin b complex, so a homebrewer, after enjoying a few home brews with good friends will drink a glass or two of water before going to bed. NO HANGOVERS. (Well, at least less likely)