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brewing Brewing is the production of beer by steeping a starch source (commonly cereal grains, the most popular of which is barley) in water and fermenting the resulting sweet liquid with yeast. It may be done in a brewery by a commercial brewer ...
and distilling, mashing is the process of combining a mix of ground
grain A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...
s – typically
malt Malt is germinated cereal grain that has been dried in a process known as " malting". The grain is made to germinate by soaking in water and is then halted from germinating further by drying with hot air. Malted grain is used to make beer, w ...
ed
barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley p ...
with supplementary grains such as corn, sorghum, rye, or
wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
– known as the " grain bill" with water and then heating the mixture. Mashing allows the
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
s in the malt (primarily, α-amylase and β-amylase) to break down the
starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human die ...
in the grain into
sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or do ...
s, typically maltose to create a malty liquid called wort. The two main methods of mashing are infusion mashing, in which the grains are heated in one vessel, and decoction mashing, in which a proportion of the grains are boiled and then returned to the mash, raising the temperature. Mashing involves pauses at certain temperatures (notably ) and takes place in a "mash tun" – an insulated brewing vessel with a false bottom.


Etymology

The term "mashing" probably originates from the
Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlers in the mid-5th ...
noun ''masc'', which means "soft mixture", and the Old English verb ''mæscan,'' which means "to mix with hot water". Usage of the term to refer to "anything reduced to a soft, pulpy consistency" is recorded as early as the late 16th century. The end product is called a "mash".


Infusion mashing

Most 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 some breweries do single-step infusions, performing only one rest before lautering.


Decoction mashing

Decoction mashing involves boiling a portion of the grains and then returning them to the mash, raising the temperature. The boiling extracts more starches from the grains by breaking down the cell walls. It 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. Decoction is a traditional method and is common in German and Central European breweries. It was used out of necessity before the invention of
thermometer A thermometer is a device that measures temperature or a temperature gradient (the degree of hotness or coldness of an object). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermometer ...
s allowed for simpler step mashing, but the practice is still in use for many traditional
beer Beer is one of the oldest and the most widely consumed type of alcoholic drink in the world, and the third most popular drink overall after water and tea. It is produced by the brewing and fermentation of starches, mainly derived from ce ...
s because of the unique malty flavor it lends to the end product. Boiling part of the grain results in
Maillard reaction The Maillard reaction ( ; ) is a chemical reaction between amino acids and reducing sugars that gives browned food its distinctive flavor. Seared steaks, fried dumplings, cookies and other kinds of biscuits, breads, toasted marshmallows, and m ...
s, which create melanoidins that create rich, malty flavors.Decoction Mashing
brewery.org


Mash tun

To achieve
economies of scale In microeconomics, economies of scale are the cost advantages that enterprises obtain due to their scale of operation, and are typically measured by the amount of output produced per unit of time. A decrease in cost per unit of output enables ...
, large breweries often possess at least one dedicated vessel for mashing, called a ''mash tun''. Breweries implementing a decoction process must possess at least two dedicated vessels. Mash tuns have a powerful stirring mechanism, known as a mash rake, to keep the temperature of the mash uniform. They also have an efficient heating method, often based on
steam Steam is a substance containing water in the gas phase, and sometimes also an aerosol of liquid water droplets, or air. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporizatio ...
, that will not scorch the malt. This heating method is combined with proper insulation enabling mash to maintain rest temperatures for up to one hour inside the vessels. A spray ball for
clean-in-place Clean-in-place (CIP) is an automated method of cleaning the interior surfaces of pipes, vessels, equipment, filters and associated fittings, without major disassembly. CIP is commonly used for equipment such as piping, tanks, and fillers. CIP emp ...
(CIP) operation helps with periodic deep cleaning. Sanitation is not a major concern before wort boiling, so a rinse-down is usually all that is necessary between batches. Smaller breweries often use a boil kettle or a lauter tun for mashing. Using a lauter tun limits the breweries to single-step infusion mashing, however, because such a vessel is not completely appropriate for the lautering process ite?/sup>.


Mashing-in

Mixing of the strike water used for mashing in and milled grist must be done in a way that minimizes clumping and oxygen uptake. This was traditionally done by first adding water to the mash vessel and then introducing the grist from the top of the vessel in a thin stream, but this 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's still in the delivery tube, reduces oxygen uptake and prevents dust from being lost. Mashing in – sometimes called "doughing-in" – is typically done between , but for single-step infusion mashes, mashing in must be done between for amylases to break down the grain's starch into sugars. The weight-to-weight ratio of strike water and grain varies from one-half for dark beers in single-step infusions to one-quarter or even one-fifth ratios that are more suitable for light-colored beers and decoction mashing, where much of the mash water is boiled off.


Enzymatic rests

In step infusion and decoction mashing, the mash is heated to different temperatures to allow specific enzymes to work optimally. The table at right shows the optimal temperature ranges for key enzymes and what materials those enzymes break down. There is some contention in the brewing industry as to the optimal temperatures 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 complete, the enzymes active in that step are denatured by the increasing heat and become permanently inactive. The time spent transitioning between rests is preferably as short as possible; however, if the temperature is raised more than 1 °C per minute, enzymes may be prematurely denatured in the transition layer near the heating elements.


β-Glucanase rest

β-glucan is a general term for polysaccharides, such as
cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wa ...
, made up of chains of
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
molecules connected by beta glycosidic bonds, as opposed to the alpha glycosidic bonds in starch. They are a major constituent of the
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mec ...
s of plants and make up a large part of the bran in grains. A β-glucanase rest done at is practiced in order to break down cell walls and make starches more available, thus raising the extraction efficiency. Should the brewer let this rest go on too long, it's possible that a large amount of β-glucan will dissolve into the mash, which could lead to a stuck mash on brew day and cause filtration problems later in beer production.


Protease rest

Protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
degradation via a proteolytic 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 ensure the amount of FAN produced can be metabolized by the yeast to avoid 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.


Amylase rests

The amylase rests are responsible for the production of free fermentable and non-fermentable sugar from starch in a mash. Starch is an enormous molecule made up of branching chains of glucose molecules.
β-amylase β-Amylase (EC 3.2.1.2 , saccharogen amylase, glycogenase) is an enzyme with the systematic name ''4-α-D-glucan maltohydrolase''. It catalyses the following reaction: : Hydrolysis of (1→4)-α-D-glucosidic linkages in polysaccharides so as to ...
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 yeast's main food source during fermentation. During this rest, starches also cluster together forming visible bodies in the mash. This clustering eases the lautering process. The α-amylase rest is also known as the saccharification rest. During this rest, the α-amylase breaks down the starches from the inside and starts cutting off links of glucose that are one to four glucose molecules in length. The longer glucose chains, sometimes called dextrins or
maltodextrins Maltodextrin is a polysaccharide that is used as a food ingredient. It is produced from vegetable starch by partial hydrolysis and is usually found as a white hygroscopic spray-dried powder. Maltodextrin is easily digestible, being absorbed as r ...
, along with the remaining branched chains give body and fullness to the beer. Because of the closeness in temperatures of peak activity of an α-amylase (63-70 °C) and β-amylase (55-65 °C), the two rests are often performed at once with the time and temperature of the rest determining the ratio of fermentable to non-fermentable sugars in the wort and, hence, the final sweetness of the fermented drink. A hotter rest results in a fuller-bodied, sweeter beer as α-amylase produces more non-fermentable sugars. is a typical rest temperature for a pale ale or German pilsener, while Bohemian pilsener and
mild ale Mild ale is a type of ale. Modern milds are mostly dark-coloured, with an alcohol by volume (ABV) of 3% to 3.6%, although there are lighter-hued as well as stronger milds, reaching 6% abv and higher. Mild originated in Britain in the 17th centur ...
are typically rested at .


Decoction "rests"

In decoction mashing, part of the mash is taken out of the mash tun and placed in a cooker, where it is boiled for a period of time. This caramelizes some of the sugars, giving the beer a deeper flavor and color, and frees more starches from the grain, making for a more efficient extraction from the grains. The portion drawn off for decoction is calculated so 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 thick mash is then boiled for around 15 minutes and returned to the mash tun. The mash cooker used in decoction should not scorch the mash, but maintaining a uniform temperature in the mash is not a priority. To prevent a scorching of the grains, the brewer must continuously stir the decoction and apply slow heating. A decoction mash brings out a higher malt profile from the grains and is typically used in Bock or Doppelbock beers.


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 less
viscous The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the in ...
, allowing the
lauter Lauter may refer to: People * Lauter (surname) Places *Lauter, Saxony, town in the district of Aue-Schwarzenberg, Saxony, Germany * Lauter, Bavaria, village in the district of Bamberg, Bavaria, Germany Rivers * Lauter (Baunach), tributary to th ...
to process faster. Although mash temperature and viscosity are roughly inversely proportional, the ability of brewers and distillers to use this relationship is constrained by the fact that α-Amylase quickly denatures above . Any starches extracted once the mash is brought above this temperature cannot be broken down and will cause a starch haze in the finished product. In larger quantities, an unpleasantly harsh flavor can develop. Therefore, the mash-out temperature rarely exceeds . If the lauter tun is a separate vessel from the mash tun, the mash is transferred to the
lauter Lauter may refer to: People * Lauter (surname) Places *Lauter, Saxony, town in the district of Aue-Schwarzenberg, Saxony, Germany * Lauter, Bavaria, village in the district of Bamberg, Bavaria, Germany Rivers * Lauter (Baunach), tributary to th ...
tun at this time. If the brewery has a combination mash-
lauter Lauter may refer to: People * Lauter (surname) Places *Lauter, Saxony, town in the district of Aue-Schwarzenberg, Saxony, Germany * Lauter, Bavaria, village in the district of Bamberg, Bavaria, Germany Rivers * Lauter (Baunach), tributary to th ...
tun, the agitator is stopped after mash-out temperature is reached and the mash has mixed enough to ensure a uniform temperature.


See also

* Grain bill * Wort * Sour mash


References


External links

* * {{Authority control Brewing