Lautering
Encyclopedia
Lautering is a process in brewing
Brewing
Brewing is the production of beer through steeping a starch source in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BCE, and archeological evidence suggests that this technique was used in ancient Egypt...

 beer
Beer
Beer is the world's most widely consumed andprobably oldest alcoholic beverage; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of sugars, mainly derived from malted cereal grains, most commonly malted barley and malted wheat...

 in which the mash
Mashing
In brewing and distilling, mashing is the process of combining a mix of milled grain , known as the "grain bill", and water, known as "liquor", and heating this mixture...

 is separated into the clear liquid wort
Wort
Wort may refer to:* Wort, the liquid created by the mashing of malted barley to use in brewing beer* Worting, Hampshire, a large district and suburb of the town of Basingstoke, in Hampshire, England....

 and the residual grain. Lautering usually consists of 3 steps: mashout, recirculation, and sparging.

Mashout

Mashout is the term for raising the temperature of the mash to 170 °F (77 °C). This both stops the enzymatic
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 conversion of starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

es to fermentable sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

s, and makes the mash and wort more fluid. Mashout is considered especially necessary if there is less than 1.5 quarts of water per pound of grain (3 liters of water per kilogram of grain), or if the grain is more than 25% wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...

 or oat
Oat
The common oat is a species of cereal grain grown for its seed, which is known by the same name . While oats are suitable for human consumption as oatmeal and rolled oats, one of the most common uses is as livestock feed...

s. The mashout step can be done by using external heat, or simply by adding hot water.

Recirculation

Recirculation consists of drawing off wort from the bottom of the mash, and adding it to the top. Lauter tuns typically have slotted bottoms to assist in the filtration process. The mash itself functions much as a sand filter
Filtration
Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids by interposing a medium through which only the fluid can pass...

 to capture mash debris and proteins. This step is monitored by use of a turbidimeter
Nephelometer
A nephelometer is a stationary or portable instrument for measuring suspended particulates in a liquid or gas colloid. A nephelometer measures suspended particulates by employing a light beam and a light detector set to one side of the source beam. Particle density is then a function of the...

 to measure solids in the wort liquid by their opacity
Opacity (optics)
Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc...

.

Sparging

Sparging is trickling water through the grain to extract sugars. This is a delicate step, as the wrong temperature or pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 will extract tannin
Tannin
A tannin is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.The term tannin refers to the use of...

s from the chaff (grain husks) as well, resulting in a bitter brew. Typically, 50% more water is used for sparging than was originally used for mashing. Sparging is typically conducted in a lauter tun.

English
English beer
English beer has a long history and traditions that are distinct from most other beer brewing countries.Beer was the first alcoholic drink to be produced in England, and has been brewed continuously since prehistoric times...

 sparging drains the wort completely from the mash, after which more water is added, held for a while at 170 °F and then drained again. The second draining can be used in making a lighter-bodied low-alcohol beer known as small beer, or can be added to the first draining. Some homebrewers use English sparging, except that the second batch of water is only held long enough for the grain bed to settle, after which recirculation and draining occurs.

German
German beer
Beer is a major part of German culture. For many years German beer was brewed in adherence to the Reinheitsgebot order or law which only permitted water, hops and malt as beer ingredients until its repeal in 1988. The order also required that beers not exclusively using barley-malts such as wheat...

 sparging, which is used by commercial breweries
Brewery
A brewery is a dedicated building for the making of beer, though beer can be made at home, and has been for much of beer's history. A company which makes beer is called either a brewery or a brewing company....

 and many homebrewers, uses continuous process sparging. When the wort reaches a desired level (typically about an inch) above the grainbed, water is added at the same slow rate that wort is being drained. The wort gradually becomes weaker and weaker, and at a certain point, they stop adding water. This results in greater yields.

Lauter tun

A lauter tun is the traditional vessel used for separation of the extracted wort
Wort
Wort may refer to:* Wort, the liquid created by the mashing of malted barley to use in brewing beer* Worting, Hampshire, a large district and suburb of the town of Basingstoke, in Hampshire, England....

.
While the basic principle of its operation has remained the same since its first use, technological advances 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 compaction of 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 spent 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 transferred 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.
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