Brewing beer is really a very simple process, a unique mix of art and science that consists of a number of key steps. Brewing begins with malted barley that is milled and mixed with hot water to form a mash.
During mashing, the malt starches are converted to sugars. The sugar-rich water is then strained through the bottom of the mash and is now called wort. The wort then goes to the brew kettle where it is brought to a boil.
During this stage, hops are added at different times during the boil for either bitterness or aroma. The wort is then cooled and aerated, and the brewers’ yeast is added for fermentation. The yeast produces alcohol and carbon dioxide and other byproducts from the sweet wort.
After fermentation the “green beer” undergoes maturation. The last step in the brewing process is filtration, and then carbonation. Next the beer is moved to a holding tank where it stays until it is bottled or kegged.
Malt
Barley malt is to beer as grapes are to wine. It is ideally suited to brewing for many reasons. Malted barley has a high complement of enzymes for converting its starch supply into simple sugars and contains protein, which is needed for yeast nutrition. Of course, one important element is its flavor. There are two types of barley: six-row and two-row.
Hops
Hops, a minor ingredient in beer, are used for their bittering, flavoring, and aroma-enhancing powers. Hops also have pronounced bacteriostatic activity that inhibits the growth of Gram-positive bacteria in the finished beer and, when in high enough concentrations, aids in the precipitation of proteins.
Brewers Yeast
Brewers yeast are responsible for converting fermentable sugars into alcohol and other byproducts. There are two types of beer yeast: ale yeast (the “top-fermenting” type) and lager yeast (the “bottom-fermenting” type). Top-fermenting yeasts are used for brewing ales, porters, stouts, Altbier, Kölsch, and wheat beers. Some of the lager styles made from bottom-fermenting yeasts are Pilsners, Dortmunders, Märzen, Bocks, and American malt liquors.
Brewing Water
The mineral content of brewing water has long been recognized as making an important contribution to the flavor of beer. This is especially important since water composes more than 90% of the beer.
A wide range of brewing waters is employed, giving rise to many classic styles of beers, that over the centuries have become world famous. For example, the famous brewing waters from the deep wells at Burton-on-Trent are known for their excellent qualities in brewing full-flavored pale ales.
Burton water is high in permanent hardness because of the high calcium and sulfate content, but it also has a lot of temporary hardness from a high level of bicarbonate. Munich water is poor in sulfates and chloride but contains carbonates, which are not very desirable for pale beers but ideal for producing darker, mellower lagers. The carbonates raise the mash pH, producing a wort with a higher dextrin to maltose ratio.
The water from Vienna is more mineralized than that of Munich. Pilsen, renowned for its pale lagers, has very soft water and produces beers famous for their pale color and hop flavor. The water of Dortmund contains appreciable amounts of both carbonate and chloride that aid in the production of full-flavored lagers and pale ales. Higher concentrations of chlorides are suitable for some mild ales and stouts, as are certain alkaline waters containing magnesium sulfate and sodium bicarbonate.
Beer Adjuncts
Adjuncts are nothing more than unmalted grains such as corn, rice, rye, oats, barley, and wheat. Although adjuncts are used mainly because they provide extract at a lower cost (a cheaper form of carbohydrate) than is available from malted barley and because they are readily available, other definite advantages are also achieved.
Malt Milling
Malted barley is crushed in the roller mill, and the resultant material is called the grist. The grist is mixed with hot water, and augered into the mash tun for mashing (in industry terms, this is called the mash). This liquefies the originally solid soluble parts of the ground malt.
Mashing
Mashing involves heating the mash or oat-meal like mixture in the mash tun in order to convert the starches in the malt, and adjuncts if added, into fermentable and unfermentable sugars.
In infusion mashing, brewers produce and recover the extract at a single temperature. Whereas in decoction mashing, portions of the mash are pumped into a kettle and boiled to facilitate protein breakdown. The mash is then pumped back into the mash tun, where the temperature is raised slowly. In a compromise between the two mashing methods, brewers use a temperature-controlled mash where the temperature is raised in steps in a single vessel.
Wort Separation
After mashing, when all the starch has been broken down, it is necessary to separate the liquid extract (the wort) from the solids (spent grain particles and adjuncts). Wort separation is important because the solids contain large amounts of protein, poorly modified starch, fatty material, silicates, and polyphenols (tannins). The objectives of wort separation (lautering) include the following:
- to produce clear wort
- to obtain good extract recovery
- to operate within the acceptable cycle time
It should be emphasized that the quality of the grist from the mill can greatly affect wort clarity, extraction recovery, and overall lauter times.
Wort Boiling
Following extraction of the carbohydrates, proteins, and yeast nutrients from the mash, the clear wort must be conditioned by boiling the wort in the kettle. The purpose of wort boiling is to stabilize the wort and extract the desirable components from the hops. The principal biochemical changes that occur during wort boiling are as follow:
- sterilization
- destruction of enzymes
- protein precipitation
- color development
- isomerization
- dissipation of volatile constituents
- concentration
- oxidation
Wort Cooling
After boiling and clarification, the wort is cooled in preparation for the addition of yeast and subsequent fermentation. The principal changes that occur during wort cooling are as follow:
- cooling the wort to yeast pitching temperature.
- the formation and separation of cold break.
- oxygenation of the wort to support yeast growth.
Fermentation
Fermentation is the process by which fermentable carbohydrates are converted by yeast into alcohol, carbon dioxide, and numerous byproducts. The byproducts have a considerable effect on the taste, aroma, and other characteristic properties of the beer. Fermentation is dependent upon the composition of the wort, the yeast, and fermentation conditions.
Wort composition, as discussed in previous chapters, influences fermentation by the presence and concentration of various nutrients, pH, and degree of aeration and temperature. These factors can affect the rate of fermentation, the extent of fermentation, the amount of yeast produced, and the quality of beer produced.
Traditionally, there are two types of beer yeast, based on their physical behavior: ale yeast (the “top-fermenting” type, Saccharomyces cerevisiae) and lager yeast (the “bottom-fermenting” type, Saccharomyces uvarum). Top-fermenting yeast flocculates and rise to the top of the fermenting wort producing a stable yeast head, while bottom-fermenting yeast flocculates and settle on the bottom of the fermenter.
However, some modern ale strains are selected for use in cylindroconical fermenters because they are poor head formers, the yeast crop being harvested from the base of the fermenter. Furthermore, some ale strains work equally well in both traditional and cylindroconical fermenters, forming a yeast head in a traditional vessel and settling to the cone at the end of fermentation in the conical vessel.
The factors that affect fermentation conditions are time, wort temperature, volume, fermenter design, pressure, agitation, and currents in the wort.
Conditioning
Following primary fermentation, many undesirable flavors and aromas are present in the “green” or immature beer. Conditioning reduces the levels of these undesirable compounds to produce a more finished product. The component processes of conditioning are:
- maturation
- clarification
- chill proofing
Filtration
Extended lagering periods and the addition of flocculation aids both greatly reduce yeast and haze loadings. Centrifuges are mainly used in the preliminary reduction of suspended particles, primarily in yeast before sending to the conditioning tanks. Although these methods are very effective in prefiltering the beer, a final filtration is needed to remove residual yeast, other turbidity-causing materials, and microorganisms in order to achieve colloidal and microbiological stability.
If there is a significant quantity of suspended material to be removed, powder filters using diatomaceous earth or perlite must be employed. Although powder filters can produce beer of acceptable brilliance after a single filtration, a two-stage filtration process is needed for a final polish. Polish filtration may employ a sheet filter, used as an intermediate step in handling heavier loads, followed by a cartridge filter.
Carbonation
The next major process which takes place after filtration and prior to packaging is carbonation. Carbon dioxide not only contributes to perceived “fullness” or “body” and enhances foaming potential, it also acts as a flavor enhancer and plays an important role in extending the shelf life of the product.
The level of dissolved carbon dioxide in beer following primary fermentation varies as a result of a number of parameters such as temperature, pressure, yeast, type of fermentation vessel, and initial wort clarity. Typically, carbon dioxide levels range from 1.2 to 1.7 volumes of carbon dioxide per volume of beer (v/v) for nonpressurized fermentations. Consequently, carbon dioxide levels need adjustment, unless the beer has undergone traditional lagering. Common practice is to raise the carbon dioxide level between 2.2 and 2.8 v/v prior to packaging.
Bottling
Once the final quality of the beer has been achieved, it is ready for packaging. The packaging of beer is one of the most complex aspects of brewery operations and the most labor-intensive of the entire production process.
Kegging
Kegs, another option in packaging beer, are used in bars and catering establishments where beer is served “on draught.” Kegging involves filling carbonated pasteurized beer into sterile aluminum or stainless steel kegs of various sizes. Aluminum kegs are generally more popular than stainless steel kegs because they are lighter and more resistant to minor damage. Compared with traditional cask ale, keg beer is more resistant to haze formation and microbial contamination. Consequently, the shelf life for keg beer is between 1 and 3 months compared with the 2 to 4 weeks for traditional cask ale. Kegging fits into the cost structure for craft brewers with limited startup capital for bottling lines and low product output.
Spoilage
Microorganisms causing spoilage during brewing and beer processing are limited to a few genera of bacteria, wild yeasts, and molds. This is because beer is a rather unfavorable growth medium for most beer spoilage microorganisms. The alcohol content, low pH, and the presence of hop constituents are inhibitory, while the lack of nutrients restricts growth of those cells which do survive. Nevertheless, these can interfere with fermentation or have deleterious effects on beer flavor and shelf life.