Beer is made from four ingredients: water, grain, hops, and yeast. Each of these ingredients can have tremendous affect on the flavor, aroma, alcohol content, and "mouth feel" of the final beer. Sometimes, adjuncts are used to add characteristic flavors, and often nutrients and agents are used improve the life cycle of the yeast.
== Water ==
Water is the largest ingredient (by volume or by weight) in the brewing process.
=== Water chemistry ===
If you are using tap water, boil the water for five minutes to remove any chlorine. This will not be sufficient to remove chloramines. Potassium Metabisulfite can be used to remove chloramine. A simple carbon filter will remove chloramines as well as other contaminants that may affect brewing or flavor.
Various minerals may be added to excessively soft water (e.g. rain water) for those recipes that require it: In particular, calcium is an essential cofactor for the enzyme alpha amylase, which is needed to turn the starch in the barley into sugars. Minerals which are often added to water include:
Gypsum (Calcium sulfate)
Epsom salts (Magnesium sulfate)
Chalk (Calcium carbonate)
== Fermentables ==
Fermentable sugars make up the primary ingredients of any beer, and are primarily obtained from grain, usually malted barley grain. Depending on the complexity of your brew, you may use barley malt, malt extract, and/or adjuncts to obtain the desired amount of fermentables in your wort (which is a sweet, unfermented liquid that can become beer, and is pronounced wert).
=== Barley Malt ===
Barley grain, or seeds, are allowed to sprout for a short amount of time and then dried to prevent further growth. This process is called malting and allows the grain to convert part of its stored starches to starches that can easily be converted to fermentable sugars, and to produce enzymes and nutrients that are important later in the brewing process. Malts are often described as under modified or fully modified and this simply refers to how long the grain was allowed germinate, and thus how well the starches have been converted and most importantly how well those nutrients have developed. Sometimes, this malted barley will be further processed by roasting, toasting, or even smoking, to allow the brewmaster to add special characteristics or complement other flavors expected in the beer.
There are two main types of barley used to make malt; two row and six row. These terms refer to the number of barley corns in the sheaf. Six row barley tends to yield a larger amount of grain per measured area of farmland, but two row generally produces larger barley corns and thus a better yield of convertible starch per measured amount of grain. However, it is generally held that six row barley will have a higher enzymatic power, which is important when using adjuncts without (or with very little of) the needed enzymes to convert their own starches during the brewing process (such as rice or corn).
Malt also varies in colour and its capacity to convert starch to sugar (diastatic power). This variation is determined by the modification level of the malt (described earlier) and by the length of time that the malt is heated after it has been germinated. Lagers and Pilseners tend to use undermodified malt, that is malt which the starch grains are relatively intact such as pale malt, while ales use more modified malts, such as crystal malts. Stouts use heavily modified malts such as chocolate, or roast barley (which technically is not a malt as it hasn't been germinated).
A note on enzymatic and diastatic powers: enzymatic power refers to the ability of the malt to convert adjunct starches, diastatic refers to its ability to convert its own starches, which are roughly the same damn thing.
=== Malt Extract ===
Malt extract is wort which has been concentrated, either by boiling down to a syrup (LME or Liquid Malt Extract) or by being spray-dried to a powder (DME or Dried Malt Extract). Depending on the source, your malt extract may be a self-contained wort concentrate, a single grain extract, or it can be described as something in between. Mountmellick Famous Irish Style Stout malt extract is an example of a self contained concentrated wort in that by simply dissolving the syrup into an appropriate amount of water you will have a fully developed wort, ready to be fermented. It has already gone through a process to extract the sugars from the grain and develop needed nutrients and flavor characteristics. Such prepared kits are invaluable to the first time homebrewer, since they will result in an acceptable beer while allowing the brewer to learn about the processes outside of the actual brewing.
However, to have more control of the flavor, body, alcohol content, and a host of other factors, a malt extract brewer will eventually start to mix and match differing amounts of different malt extracts that have been concentrated from liquid rich in fermentable sugars from differing amounts of barley malts and adjuncts. These malt extracts come from batches with varying degrees of plain malted barley, of varying degrees of modification, roasted barley malt, wheat malt and flakes, rice, corn, many other forms of grain, and even cane sugar. Often these extracts are sold without much indication of what went into them, merely saying "Amber LME," "dark LME," "Light DME" and so forth. While most extract recipes will also use such vague terminology, it might benefit the brewer to request information regarding the ingredients, since certain types of sugars can impart unwanted flavors in a beer if present in too large proportions.
=== Adjuncts ===
Adjuncts are sources of fermentable sugars that are not barley. Adjuncts should be used to add unique flavors, aromas, and head retention and body characteristics to a beer. Adjuncts can also be used to increase alcohol content, lower production costs, and add "blanding" characteristics. Major commercial breweries use adjuncts such as corn and rice to reduce production costs and, in conjunction with other techniques and additives, create a consistent but boring tasting beer. This allows them to produce a beer that will be accepted by a wider range of people, and keeping them, while using a minimal amount of capital. While this is good for business, as a home-brewer you are not going to sell your beer, so you should be concerned with what you like. You will likely find that you prefer unique flavors of your own devising to the lower cost of a simpler beer.
Commonly used adjuncts:
Barley - Unmalted barley can contribute to head retention.
Cane Sugar - Yes, cane sugar can be used to increase fermentables, but can (and usually will) impart a "cidery" taste to the finished beer.
Corn - Corn starch can lighten the flavor and body of the beer. Some brewmasters claim it has a stabilizing affect on the flavor.
Honey - If added at the beginning of the boil, the sugars in honey will break down become fermentable, however the most potent parts of the honey flavor will then be lost.
Oats - Oats can add a meaty, heavy body flavor to a beer. Yes it will taste like oatmeal.
Potato - A relatively neutral adjunct that can increase the amount of fermentables in the wort at low cost.
Rice - Like corn, rice can lighten the flavor and body of the beer.
Rye - Unmalted rye contributes a dry, crisp character.
Wheat - Wheat malt can impart a sour flavor, unmalted wheat flour or flakes can assist head retention
== Hops ==
The use of hops is one of, if not the most, important differences in the production of beer from the production of other alcoholic drinks. Without the bittering effect of hops, beer would be nothing more than a low alcohol wine made from barley (in fact, with a more alcohol-resistant strain of yeast and a slightly higher amount of fermentables, it would be a wine). Hops are used for three basic reasons: bittering, flavouring, and aroma. They also have somewhat of a preservative effect, although the extent of this effect is debated. In the days before refrigeration, shipments of beer on long voyages would often sour or spoil, due to bacterial or fungal infection or simply due to aging. Breweries often would steep herbs and plants in the unfermented wort to inhibit this spoilage and stabilize the flavour of the beer. Hops simply won out due to the popularity of the flavor, and the benefits it provided, such as improved head retention, clarification, and the counteraction to the sweet, sticky taste beer had otherwise.
Some examples of hop varieties are Hallertau Mittelfrueh, Tettnang, Spalt, Saaz, Mt. Hood, Perle, and Cascade, and they are available in whole form and pellets.
=== Bittering ===
The bitterness in a beer comes mainly from the alpha acid resins present in the hop flower, or cone. Hops are usually labelled according to % alpha acid, which can be used to determine the amount of a given kind of hops to produce a given level of bitterness.
Brewing scientists use International Bitterness Units (IBUs) in their calculations of the bitterness of a given beer. The units describe the amount of alpha acids per liter of wort. However, IBUs do not completely reflect the bitterness perceived in a beer because a given IBU in a light bodied beer will taste much more bitter than a heavy bodied beer with the same IBU. The alpha acids counteract the sweet flavors of the sugars, so the more sugars available, the more alpha acids required to counteract them.
A simpler method used in recipes is the Homebrew Bitterness Unit (HBU), which is simply the % alpha acid × the ounces of hops. Since hops of the same variety can vary from year to year in % alpha acid, this measurement can be useful to maintain consistency in the bitterness of a given recipe. Another unit that can be used is Metric Bitterness Units (MBU) which is calculated exactly as HBUs, but using grams instead of ounces.
Bitterness is extracted by boiling the hops in the wort for an hour or more. The alpha acids require the high temperature for so long to allow isomerization to occur, which is just a fancy word to describe the chemical reaction that causes the alpha acids to dissolve into the wort. The longer this reaction is allowed to occur, the better the utilization of the alpha acids will be, since more of it will be extracted.
=== Flavouring and Aroma ===
Hops also contain hop oils that have strong tastes and smells that many home-brewers find quite desirable. These oils, unlike alpha acids, are water soluble, and can quickly be extracted. However, because they are soluble, they will also "boil away." So, to get the desirable flavors and aromas into the beer, Flavoring and aroma hops are added near the end of the boil, sometimes in two stages, and less often a brew master may "dry hop" the fermenting beer.
== Yeast ==
Yeast is technically an ingredient, but yet it really isn't. Yeast can be thought of as the machine by which wort is turned into beer. Before the discovery of yeast, this process was considered somewhat magical, and beer was often fermented by wild strains of yeast, and sometimes by a strain of yeast found on a family's stir stick or in previously used fermentation barrels. In fact, the Reinheitsgebot of Germany stated that the only permissible ingredients in beer were barley, hops, and water. Often, fermenting beer would get contaminated with bacteria and/or undesirable strains of yeast, and barrels would be burned - not because of the contamination but because the barrel was "cursed." A "stir stick" that was used in successful batches of beer would be considered blessed and would be treasured by its owners, not realizing that it was just infected with a desirable strain of yeast.
There are two main types of beer yeast; Ale and Lager. Ale yeast is top-fermenting and prefers temperatures from 60–70°F (15 - 21°C). Ales are typically more complex than lagers, with more flavour and aroma components. Lager yeast is bottom-fermenting and prefers cooler temperatures. It typically results in a cleaner tasting beer, without the estery character common to ales.
Yeast comes in two main forms, dried and liquid. Dried yeast can be of very good quality (avoid that which comes with tins of malt extract, though), and is often more quickly active in a beer. It can produce a limited range of ales—beware that no dried yeast is truly a lager yeast, nor will it provide the distinctive lager character. Dried yeasts are generally more effective if rehydrated prior to use. Liquid yeasts are harder to store as they must be kept chilled prior to use. There are many more strains of liquid yeast, and thus one can much more exactly reproduce a particular beer or style. Dried yeast is typically used by beginners and liquid yeast by more advanced brewers, although there are exceptions on either end of the scale.
== Water ==