1.3 The modern brewery

Breweries today are made predominantly of stainless steel, although vessels often have a decorative copper clading for a nostalgic look. Stainless steel has many favorable characteristics which make it a well-suited material for brewing equipment. It imparts no flavor in beer, it reacts with very few chemicals, which means almost any cleaning solution can be used on it (concentraited cholorine being a notable exception) and it is very sturdy. Sturdiness is important, as most tanks in the brewery have positive pressure applied to them as a matter of course, and it is not unusual that a vaccum will be formed incidentally during cleaning.

Heating in the brewhouse is usually achieved through pressurized steam, although direct-fire systems are not unusual in small breweries. Similarly, cooling in other areas of the brewery is typically done by cooling jackets on tanks, which allow the brewer to precicely control the temperature on each tank individually, although whole-room cooling is also common.

Today modern brewing plants perform myriad analyses on their beers for quality control purposes. Shipments of ingredients are analyized in order to correct for variations; Samples are pulled at almost every step and tested for oxygen content, unwanted microbial infections, and other beer-aging compounds; and a representitive sample of the finished product is often stored for months for comparison when complains are filed.

2 The Brewing Process

Work in the brewery is typically divided into 7 steps: Mashing, Lautering, Boiling, Fermenting, Conditioning, Filtering, and Filling.

2.1 Mashing

Mashing is the process of mixing milled grain (typically malted grain) 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.

Large breweries usually employ a decoction mash method, in which the thickest part of the mash is boiled to extract more starch from the grain, then returned to the mash to achieve the next rest temperature. These can be classified into one-, two-, and three-step decoctions, depending on how many times part of the mash is drawn off to be boiled. Smaller breweries use infusion mashing, in which the mash is heated directly to go from rest temperature to rest temperature. Some infusion mashes achieve temperature changes by adding hot water, and there are also breweries that do single-step infusion, performing only one rest before lautering. It is important to note that fancy equipment and methods do not guarantee a good beer. Many wonderful beers are produced on inexpensive, bare-bones equipment, and some bad beers are produced in breweries that are state-of-the-art.

In large breweries, in which optimal utilization of the brewery equipment is economically necessary, there is at least one dedicated vessel for mashing. In decoction processes there must be at least two. The vessel is has a good stirring mechanism to keep the temperature of the mash uniform, and a heating device which is effecient, but will not scorch the malt, and should be insulated to maintain rest temperatures for up to one hour. A spray ball for clean-in-place (CIP) operation should also be included for periodical deep cleaning. Sanitation is not a major concern before wort boiling, so a rinse-down should be all that is necessary between batches.

Smaller breweries often use the boil kettle for mashing, or use the lauter tun. The latter case either limits the brewer to single-step infusion mashing, or leaves the brewer with a lauter tun which is not completely appropriate for the lautering process.

2.1.1 Grain milling

The grain used for making beer must first be milled. Milling increases the surface area of the grain, making the starch more accessible, and separates the seed from the husk. Care must be taken when milling to ensure that the starch reserves are sufficently milled without damaging the husk and providing coarse enough grits that a good filter bed can be formed during lautering.

Grains are typically dry milled. Dry mills come in four varieties: two-, four-, five-, and six-roller mills. Hammer mills, which produce a very fine mash, are often used when mash filters are going to be employed in the Lautering process because the grain does not have to form its own filterbed. In modern plants, the grain is often conditioned with water before it is milled to make the husk more pliable, thus reducing breakage and improving lauter speed.

2.1.1.1 Two-roller mills

Two-roller mills are the simplest variety, in which the grain is crushed between two rollers before it continues on to the mash tun. The spacing between these two rollers can be adjusted by the operator. Thinner spacing usually leads to better extraction, but breaks more husk and leads to a longer lauter.

2.1.1.2 Four-roller mills

Four-roller mills have two sets of rollers. The grain first goes through rollers with a rather wide gap, which separates the seed from the husk without much damage to the husk, but leaves large grits. Flour is sieved out of the cracked grain, and then the coarse grist and husks are sent through the second set of rollers, which further crush the grist without damaging the crusts. There are three-roller mills, in which one of the rollers is used twice, but they are not recognized by the German brewing industry.

2.1.1.3 Five- and Six-roller mills

Six-roller mills have three sets of rollers. The first roller crushes the whole kernel, and its output is divided three ways: flour immediately is sent out the mill, grits without a hust proceed to the last roller, and husk, possibly still containing parts of the seed, go to the second set of rollers. From the second roller flour is directly output, are are husks and any possible seed still in them, and the husk-free grits are channeled into the last roller. Five-roller mills are basically six-roller mills in which one of the rollers performs double-duty.

2.1.2 Mashing-in

Mixing of the strike water, water used for mashing in, and milled grist must be done in a such a way as to minimize clumping and oxygen uptake. Traditionally this was done by first adding water to the mash vessel, and then introducing the grist from the top of the vessel in a thin stream. This unfortunately led to a lot of oxygen absorption, and loss of flour dust to the surrounding air. A premasher, which mixes the grist with mash-in temperature water while it is still in the delivery tube, reduces oxygen uptake and prevents dust from being lost.

Mashing in is typically done between 35 °C and 45 °C, but for single-step infusion mashes mashing in must be done between 62 °C and 67 °C for amylases to break down the grain's starch into sugars. The weight-to-weight ratio of strike water and grain varies from 1:2 for dark beers in single-step infusions to 1:4 or even 1:5, ratios more suitable for light-colored beers and decoction mashing, where much mash water is boiled off.

2.1.3 Enzymatic rests

Optimal rest temperatures for major mashing enzymes

Temp	Enzyme	Breaks down
40°C	β-Glucanase	β-Glucan
50°C	Protease	Protein
62°C	β-Amylase	Starch
72°C	α-Amylase	Starch

In step-infusion and decoction mashing, the mash is heated to different temperatures, at which specific enzymes work optimally. The table at right shows displays the optimal temperature for the enymes brewers most pay attention to, and what material those enzymes break down. There is some contention in the brewing industry as to just what the optimal temperature is for these enzymes, as it is often very dependent on the pH of the mash, and its thickness. A thicker mash acts as a buffer for the enzymes. Once a step is passed, the enzymes active in that step are denatured, and become permanently inactive. The time between rests is preferably as short as possible, but if the temperature is raised more than 1C° per minute, enzymes may be prematurely denatured in the transition layer near heating elements.

2.1.3.1 β-Glucanase rest

β-Glucan is a chain of the beta isomer of glucose molecules, and found mainly in the cell walls of plants, and in this context is also known as cellulose. A β-Glucanase rest done at 40°C is practiced in order to break down cell walls and make starches more available, thus raising the extraction efficency. Should the brewer let this rest go on too long, it is possible that a large amount of β-Glucan will dissolve into the mash, which can lead to a stuck mash on brew day, and cause filtration problems later in beer production.

2.1.3.2 Protease rest

Protein degradation via a protease rest plays many roles: production of free-amino nitrogen (FAN) for yeast nutrition, freeing of small proteins from larger proteins for foam stability in the finished product, and reduction of haze-causing proteins for easier filtration and increased beer clarity. In all-malt beers, the malt already provides enough protein for good head retention, and the brewer needs to worry more about more FAN being produced than the yeast can metabolize, leading to off flavors. The haze causing proteins are also more prevalent in all-malt beers, and the brewer must strike a balance between breaking down these proteins, and limiting FAN production.

2.1.3.3 β-Amylase rest

Starch is an enormous molecule made up of branching chains of glucose molecules. β-Amylase breaks down these chains from the end molecules forming links of two glucose molecules, i.e. maltose. β-Amylase cannot break down the branch points, although some help is found here through low α-Amylase activity and enzymes such as limit dextrinase. The maltose will be the yeasts main food source during fermentation. During this rest starches also cluster together forming visible bodies in the mash. This clustering eases the lautering process.

2.1.3.4 α-Amylase rest

The α-Amylase rest is also known as the saccrification rest, because during this rest the α-Amylase breaks down the starches from the inside, and starts cutting off links of glucose one to four glucose molecules in length. The longer glucose chains, along with the remaining branched chains, give body and fullness to the beer.

2.1.3.5 Decoction "rests"

In decoction part of the mash is taken out of the mash tun and placed in a cooker, where it is boiled for a predetermined amount of time. This caramelizes some of the sugars, given the beer a deeper flavor and color, and frees more starches from the grain, making for a more effecient extraction from the grains. The portion drawn off for decoction is calculated so that the next rest temperature is reached by simply putting the boiled portion back into the mash tun. Before drawing off for decoction, the mash is allowed to settle a bit, and the thicker part is typically taken out for decoction, as the enzymes have dissolved in the liquid, and the starches to be freed are in the grains, not the liquid. This thickmash is then boiled for around 15 minutes, and returned to the mash tun.

The mash cooker used in decoction should not be allowed to scortch the mash, but maintaining a uniform temperature in the mash is not a priority.

2.1.4 Mash-out

After the enzyme rests the mash is raised to its mash out temperature. This frees up about 2% more starch, and makes the mash more viscous, allowing the lauter to process faster. It would be nice to raise the mash to 100°C for mash out and have a very viscous liquid, but α-Amylase quickly denatures above 78°C and any starches extracted above this temperature cannot be broken down and will cause a starch haze in the finished product, or in larger quantities an unpleasantly harsh taste can evolve. Therefore the mash out temperature rarely exceeds 78°C.

If the lauter tun is a separate vessel from the mash tun, the mash is transferred to the lauter tun at this time. If the brewery has a combination mash-lauter tun, the agitator is stopped after mash-out temperature is reached and the mash has mixed enough to ensure a uniform temperature.

2.2 Lautering

Lautering is the separation of the extracts won during mashing from the spent grain. It is achieved in either a Lauter tun, a wide vessel with a false bottom, or a mash filter, a plate-and-frame filter designed for this kind of separation. Lautering has two stages: first wort run-off, during which the extract is separated in an undiluted state from the spent grains, and sparging, in which extract which remains with the grains is rinsed off with hot water.

2.2.1 Lauter Tun

A lauter tun is the tradional vessel used for separation of the extracted wort. While the basic principle of its operation has remained the same since its first use, technological advanced have led to better designed lauter tuns capable of quicker and more complete extraction of the sugars from the grain.

The false bottom in a lauter tun has thin (0.7 to 1.1 mm) slits to hold back the solids and allow liquids to pass through. The solids, not the false bottom, form a filtration medium and hold back small solids, allowing the otherwise cloudy mash to run out of the lauter tun as a clear liquid. The false bottom of a lauter tun is today made of wedge wire, which can provide a free-flow surface of up to 12% of the bottom of the tun.

The run off tubes should be evenly distributed across the bottom, with one tube servicing about 1 m² of area. Typically these tubes have a wide, shallow cone around them to prevent drastic forces from compacting the grain directly above the outlet. In the past the run-off tubes flowed through swan-neck valves into a wort collection grant. While visually stunning, this system led to a lot of oxygen uptake. Such a system has mostly been replaced either by a central wort-collection vessel or the arrangement of outlet ports into concentric zones, with each zone having a ring-shaped collection pipe. Brewhouses in plain public view, particularly those in brewpubs, often maintain the swan-neck valves and grant for their visual effect.

A quality lauter tun has rotating rake arms with a central drive unit. Depending on the size of the lauter tun, there can be between two and six rake arms. Cutting blades hang from these arms. The blade is usually wavy and has a plough-like foot. Each blade has its own path around the tun and the whole rake assembly can be raised and lowered. Attached to each of these arms is a flap which can be raised and lowered for pushing the spend grains out of the tun. The brewer, or better yet an automated system, can raise and lower the rake arms depending on the turbidity (cloudiness) of the run-off, and the tightness of the grain bed, as measured by the pressure difference between the top and bottom of the grain bed.

There must be a system for introducing sparge water into the lauter tun. Most systems have a ring of spray heads that insure an even and gentle introduction of the sparge water. The watering system should not beat down on the grain bed and form a channel.

Large breweries have self-closing inlets on the bottom of the tun through which the mash is transfered to the lauter tun, and one outlet, also on the bottom of the tun, into which the spent grains fall after lautering is complete. Craft breweries often have manways on the side of the mash tun for spent grain removal, which then must be helped along to a large extent by the brewer.

Some small breweries use a combination mash/lauter tun, in which the rake system cannot be implemented because the mixing mechanism for mashing is of higher importance. The stirring blades can be used as an ersatz rake, but typically they cannot be moved up and down, and would disturb the bed too much were they used deep in the grain bed.

2.2.2 Mash Filter

A mash filter is a plate-and-frame filter. The empty frames contain the mash, including the spend grains, and have a capacity of around one hectoliter. The plates contain a support structure for the filter cloth The plates, frames, and filter cloths are arrainged in a carrier frame like so: frame, cloth, plate, cloth, with plates at each end of the structure. Newer mash filters have bladders that can press the liquid out of the grains between spargings. The grain does not act like a filtration medium in a mash filter.

2.3 Boiling

Boiling the won extracts, called wort, ensures its sterility, and thus prevents a lot of infections. During the boil hops are added, which contribute their bitter aromas and flavor compounds to the beer, and, along with the heat of the boil, causes proteins in the wort to coagulate and the pH of the wort to fall. Finally, the vapors produced during the boil volitize off flavors, including dimethyl sulfide precursors.

The boil must be conducted so that is it even and intense. The boil lasts between 60 and 120 minutes, depending on its intensity, the hop addition schedule, and volume of wort the brewer expects to evaporate.

2.3.1 Boiling Equipment

The simplest boil kettles are direct-fired, with a burner underneath. These can produce a vigorous and favorable boil, but are also apt to scorch the wort where the flame touches the kettle, causing caramelization and making clean up difficult.

Most breweries use a steam-fired kettle, which uses steam jackets in the kettle to boil the wort. The steam is delivered under pressure by an external boiler.

State-of-the-art breweries today use many interesting boiling methods, all of which achieve a more intense boiling and a more complete realization of the goals of boiling.

Many breweries have a boiling unit outside of the kettle, sometimes called a calandria, through which wort is pumped. The unit is usually a tall, thin cylinder, with many tubes upwards through it. These tubes provide an enormous surface area on which vapor bubbles can nucleate, and thus provides for excellent volitization. The total volume of wort is circulated seven to twelve times an hour through this external boiler, insuring that the wort is evenly boiled by the end of the boil. The wort is then boiled in the kettle at atmospheric pressure, and through careful control the the inlets and outlets on the external boiler, an overpressure can be achieve in the external boiler, raising the boiling point a few Celsius degrees. Upon return to the boil kettle, a vigorous vaporization occurs. The higher temperature is increase vaporization can reduce boil times up to 30%. External boilers were originally designed to improve performace of kettles which did not provide adequate boiling effect, but have since been adopted by the industry as a sole means of boiling wort.

Modern brewhouses can also be equiped with internal calandria, which requires no pump. It works on basically the same principle as external units, but relies on convection to move wort through the boiler. This can prevent overboiling, as a deflector above the boiler reduces foaming, and also reduces evaporation. Internal calandria are generally difficult to clean.

2.3.2 Energy Recovery

Boiling wort takes a lot of energy, and it is wasteful to let this energy escape into the atmosphere. The simplest was to recover this energy is with a kettle vapor condenser (German: Pfaduko, from the really long word Pfannendunstkondensator). A kettle vapor condenser is often nothing more than a plate heat exchanger.

2.3.3 Whirlpool

At the end of the boil, the wort is set into a whirlpool. The so-called teacup effect forces the more dense soilds (coagualted proteins, vegetable matter from hops) into a cone in the centerof 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 tangental inlet near the bottom of the whirlpool, and a outlet on the bottom near the outer edge of the whirlpool. A whirlpool should have no internal protrusions that might slow down the rotation of the liquid. The bottom of the whirlpool is often slightly sloped towards the outlet. Newer whirlpools often have "Denk rings" suspended in the middle of the whirlpool. These rings are aligned horizontally and have about 75% of the diameter of the whirlpool. The Denk rinks prevent the formations of secondary eddies in the whirlpool, encouraging the formation of a cohesive trub cone in the middle of the whirlpool.

Smaller breweries often use the brewkettle as a whirlpool.

2.3.4 Wort Cooling

After the whirlpool, the wort must be brought down to fermentation temperatures before yeast is added. In modern breweries this is achieved through a plate heat exchanger. A plate heat exchanger has many ridged plates, which form two separate paths. The wort is pumped into the heat exchanger, and goes through every other gap between the plates. The cooling medium, usually water, goes through the other gaps. The ridges in the plates ensure turbulent flow. A good heat exchanger can drop 95°C wort to 20°C while warming the slightly more cooling medium from about 10°C to 80°C. The last few plates often use a cooling medium which can be cooled to below the freezing point, which allows a finer control over the wort-out temperature, and also enables cooling to around 10°C. After cooling, oxygen is often dissolved into the wort to revitalize the yeast and aid its reproduction.

2.4 Fermenting

Fermentation, as a step in the brewing process, starts as soon as yeast is added to the cooled wort. This is also the point at which the product is first called beer. It is during this stage that sugars won from the malt are metabolized into alcohol and carbon dioxide. Fermentation tanks come in all sorts of forms, from enormous tanks which can look like silos, to five gallon glass carboys in a homebrewer's closet.

Most breweries today use cylindroconical vessels, or CCVs, have a concial bottom and a cylindrical top. The cone's aperture is typically around 60°, an angle that will allow the yeast to flow towards the cones apex, but is not so steep as to take up too much vertical space. CCVs can handle both fermenting and conditioning in the same tank. At the end of fermentation, the yeast and other solids which have fallen to the cones apex can be simply flushed out a port at the apex.

Open fermentation vessels are also used, often for show in brewpubs, and in Europe in wheat beer fermentation. These vessels have no tops, which makes harvesting top fermenting yeasts very easy. The open tops of the vessels make the risk of infection greater, but with proper cleaning procedures and careful protocol about who enters fermentation chambers when, the risk can be well controlled.

Fermentation tanks are typically made of stainless steel. If they are simple cylindrical tanks with beveled ends, they are arranged vertically, as opposed to conditioning tanks which are usually laid out horizontally.

A very few breweries still use wooden vats for fermentation, but wood is difficult to keep clean and infection-free, and must be repitched more or less yearly.

After high kraeusen a bung device (German: Spundapparat) is often put on the tanks to allow the C O ₂ produced by the yeast to naturally carbonate the beer. This bung device can be set to a given pressure to match the type of beer being produced. The more pressure the bung holds back, the more carbonated the beer becomes.

2.5 Conditioning

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. At this stage the beer is cooled to around freezing, which encourages settling of the yeast, and causes proteins to coagulate and settle out with the yeast. Unpleasant flavors such as phenolic compounds become unsoluable in the cold beer, and the beer's flavor becomes smoother. During this time pressure is maintained on the tanks to prevent the beer from going flat.

If the fermentation tanks have cooling jackets on them, as opposed to the whole fermentation cellar being cooled, conditioning can take place in the same tank as fermentation. Otherwise separate tanks (in a separate cellar) must be employed.

2.6 Filtering

Filtering the beer stabilizes the flavor, and gives beer its polished shine and brilliance. Not all beer is filtered. When tax determination is required by local laws, it is typically done at this stage in offically calibrated tank.

Filters come in many types. Many use pre-made filtration media such as sheets or candles, while others use a fine powder made of, for example, diatomaceous earth, also called kieselguhr, which is introduced into the beer and recirculated past screens to form a filtration bed.

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. Normally used filtration ratings are divided into rough, fine and sterile. Rough filtration leaves some cloudiness in the beer, but it is noticibly clearer than unfiltered beer. Fine filtration gives a glass of beer that you could read a newspaper through, with no noticible cloudiness. Finally, as its name implies, sterile filtration is fine enough that almost all microorganisms in the beer are removed during the filtration process.

2.6.1 Plate and Frame and Candle Filters

These filters use pre-made media are relatively straight-forward. The membranes are manufactured to allow only particles smaller than a given size through, and the brewer is free to choose how finely to filter the beer. The membranes are placed into the filtering frame, sterilized (with hot water, for example) and then used to filter the beer. The membranes can be flushed if it becomes blocked, but usually these membranes are disposable and are replaced between filtration sessions.

It should be kept in mind that pre-made filters have two sides. One with loose holes, and the other with tight holes. Flow goes from the side with loose holes to the side with the tight holes. The hope is that large particles get stuck in the large holes while leaving enough room around the particles and filter medium for smaller particles to go through and get stuck in tighter holes.

2.6.2 Kieselguhr Filters

Filters that use a powder medium are considerably more complicated to operate, but can filter much more beer before needing to be regenerated.

2.7 Packaging

Packaging is putting the beer into the containers in which it will leave the brewery. Typically this means in bottles and kegs, but it might include bulk tanks for high-volume customers.

3 Craft Brewing

4 See also

• Brewing
• Beer
• Malt
• Hops
• List of breweries

5 References

• BooksEnthsiast.com: Technology Brewing and Malting, Wolfgang Kunze, 2nd revised edtion, VLB Berlin. Available at their website

Beer

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