All beers are brewed using a process based on a simple formula. Key to the process is malted grain—depending on the region, traditionally barley, wheat or sometimes rye. Brewing has a very long history, and archeological evidence suggests that this technique was used in ancient Egypt.
Beer Brewing Ingredients
The four main ingredients in beer brewing are barley malt, water, hops, and yeast. According to the German purity law called the Reinheitsgebot these are the only four ingredients allowed in beer. While microbreweries and larger breweries a like do adhere to this law, certain beers, call for other flavoring agents to achieve a more signature taste depending on the type of beer being brewed. The basic ingredients of beer are water; a starch source, such as malted barley, able to be fermented (converted into alcohol); a brewer's yeast to produce the fermentation; and a flavouring such as hops. The amount of each starch source in a beer recipe is collectively called the grain bill.
Barley is a cereal grain like oats, rice, wheat, sorghum, and corn. Barley must be malted in order to be used in the brewing process. To make malt one must soak the grain in water and allow it to start to germinate. This process is call steeping. Water is taken up by the kernels and the plant begins to grow. Starch conversion also begins during this stage, although on a very small scale. Then the kernel is kilned to stop the germination. Kilning is the drying of the malt kernels. The length of time that the kernels are kilned determines the final color of the malt. The germination process is very important to the brewer because this is when the enzymes used in the brewing process are formed. Malt is made by allowing a grain to germinate, after which it is then dried in a kiln and sometimes roasted. The germination process creates a number of enzymes which convert the starch in the grain into sugar. Depending on the amount of roasting, the malt will take on a dark colour and strongly influence the colour and flavour of the beer.
Water is extremely important in the brewing process. The brewing process uses, on average, 6.5 volumes of water to make one volume of beer. There are three types of water: Product, Process, and Service. Product water is the water used in the actual beverage. Approximately 92% of beer is water. Process water is cleaning and sanitization water for all tanks, brewing vessels, hoses, and product lines. Service water is used primarily with systems using steam as a heat transfer medium. Steam acts to heat the kettle and is used to transfer heat throughout some breweries. Many microbreweries use a direct-fire, 400,000 btu burner to heat the kettle.
With the advent of civilization (which, incidentally, many scholars believe was directly tied to the creation of some of the first beers) many things were added to beer in an attempt to enhance the flavor and preserve the final product. This was a terrifying and experimental time for beer – without careful management of the beer additives, things could get wonky. People added all sorts of things including common table salt, iron, strychnine (not for long), various fruits, and herbs. Hops were chosen for a number of reasons. They are thought to have an antimicrobial effect that helps preserve the beer. This coincides with ethanol produced in the brewing process to keep the final product free from contamination. Hops are added directly into the kettle and the heat extracts a unique bitterness and certain aromatic agents that enhance the palatability of the beer (i.e. the “nummers” factor). Bitterness and aroma depend of the variety of the hops. They are grown in all parts of the world because the world wants beer!
Yeast is the microorganism that is responsible for fermentation in beer. Yeast metabolises the sugars extracted from grains, which produces alcohol and carbon dioxide, and thereby turns wort into beer. Early beer was made as far back as 5000 B.C. in Egypt. It is only a relatively recent discovery that yeast is a vital component in making beer. Yeast converts simple sugars into ethanol and carbon dioxide in the absence of oxygen in a process called fermentation. Brewing yeasts are labeled into three categories: Ale, Lager, and Weizen (wheat) yeasts.
The brewing process is typically divided into 7 steps: mashing, lautering, boiling, fermenting, conditioning, filtering, and filling. Today, many simplified brewing systems exist which can be used at home or in restaurants. These homebrewing systems are often employed for ease of use, although some people still prefer to do the entire brewing process themselves.
Milling consists of crushing the grains. They are basically smooshed in half to expose the sugars inside. The idea is to break the grain in half and leave the husk (outer covering) intact. The husk acts like a filter later in the process. The malt is now called grist.
After milling, the grist falls into a hopper where the Auger transports it up into a vessel called the mash tun.
Mashing is the process of combining a mix of milled grain, known as the grist with water, and heating this mixture up with rests at certain temperatures to allow enzymes in the malt to break down the starch in the grain into sugars, typically maltose. Grist is combined in the mash tun with hot water from the hot liquor tank and then that mix is called "the mash." This mixture looks and feels like oatmeal. Here the mash sits at an ideal temperature of 150°F. This is when the enzymes from malting come alive and convert complex carbohydrates into simple sugars. The majority of these sugars are maltose. The mash tun has a false floor (basically a grating) at the bottom. This allows us to remove the sugar solution while keeping the husks and grain in the mash tun. This is also where the husks act as a filter. After an hour, the sugar solution is removed, now called wort (say it with me, WERT) and pump it into the kettle. The spent grain (now weighing well over 1000 pounds) is then hand-shoveled into a cart and donated to Iowa State University to feed research cattle.
Wort separation is the separation of the wort containing the sugar extracted during mashing from the spent grain. It can be carried out in a mash tun outfitted with a false bottom, a lauter tun, a special-purpose wide vessel with a false bottom and rotating cutters to facilitate flow, a mash filter, a plate-and-frame filter designed for this kind of separation, or in a Strainmaster.
Wort enters the kettle at about 155°F and is heated to 212°F. Typically, many recipes require a boil of one hour, though many other varieties of beer need longer boils to properly concentrate the fermentable sugars. Once the boil begins, hops, flavoring agents, and fining agents are added at different times during the boil. Early hop additions contribute to the final bitterness, while later additions add more aromatic qualities. State-of-the-art breweries today use many interesting boiling methods, all of which achieve a more intense boiling and a more complete realisation of the goals of boiling.
At the end of the boil, the wort is set into a whirlpool. The so-called teacup effect forces the denser solids into a cone in the center of the whirlpool tank. In most large breweries, there is a separate tank for whirlpooling. These tanks have a large diameter to encourage settling, a flat bottom, a tangential inlet near the bottom of the whirlpool, and an outlet on the bottom near the outer edge of the whirlpool. Smaller breweries often use the brewkettle as a whirlpool. In homebrewing, where a brewer has the power to lift the entire stock and manipulate it by hand; the process of trub removal (the process addressed by the whirlpool and hopback) is generally accomplished by simply allowing the trub to settle to the bottom of the brew kettle and slowly decanting the wort from the top so as not to disturb the thin layer of trub. Siphoning may also be employed but this is rare.
The wort must now be cooled before yeast is added to prevent the yeast from dying when it is added to the wort. It is brought from boiling (212ºF) to about 65ºF. Cold water is pumped through the heat exchanger on one side whilst the hopped wort is pumped through the heat exchanger in the opposite direction. The two liquids never touch, but there is a tremendous heat transfer from the wort to the cold water. This allows the wort to enter the fermenter at a safe temperature for yeast. After cooling, oxygen is often dissolved into the wort to revitalize the yeast and aid its reproduction.
After the wort is cooled and aerated, usually with sterile air, yeast is added to it, and it begins to ferment. Ale yeast traditionally ferments at ~62ºF. Ale yeast also floats to the surface after the sugars in the wort have been used up. Lager yeast sinks to the bottom when the sugar supply is exhausted and ferments at colder temperatures ~50ºF. This is the main difference between the two types of beer. Ale and Lager represent two huge families. Color is not a determination between ale or lager – the process is. Fermentation at colder temperatures takes longer to complete. A lager takes 4-6 weeks to finish and age. Ales take about two weeks to finish.
Filter and Carbonation
Filtering the beer stabilizes the flavour, and gives beer its polished shine and brilliance. From the fermenter some beers will go through a filter (not all beer is filtered, wheat beer is not filtered), this helps to clarify the beer. Filters range from rough filters that remove much of the yeast and any solids (e.g. hops, grain particles) left in the beer, to filters tight enough to strain color and body from the beer.
Ageing and Conditioning
After carbonation, the beer is stored in a serving vessel. When the sugars in the fermenting beer have been almost completely digested, the fermentation slows down and the yeast starts to settle to the bottom of the tank. Ageing (secondary fermentation) depends on the product and the type of beer. For the secondary fermentation, the beer is transferred to a second fermenter, so that it is no longer exposed to the dead yeast and other debris (also known as "trub") that have settled to the bottom of the primary fermenter. This prevents the formation of unwanted flavors and harmful compounds such as acetylaldehydes, which are commonly blamed for hangovers. During secondary fermentation, most of the remaining yeast will settle to the bottom of the second fermenter, yielding a less hazy product. Some beers may have three fermentations, the third being the bottle fermentation.
Bottle, Keg, or at the Pub
The beer travels directly from the serving vessels to the either the taps at the pub in a microbrewery/brewpub, a keg, or reaches the bottling line. Most homebrewed beers undergo a fermentation in the bottle, giving natural carbonation. This may be a second or third fermentation. They are bottled with a viable yeast population in suspension. Cask ale or cask-conditioned beer is the term for unfiltered and unpasteurised beer which is conditioned (including secondary fermentation) and served from a cask without additional nitrogen or carbon dioxide pressure.