Mashing Process, Techniques

T13. Explain what happens during the mashing process. Describe three different mashing techniques and the advantages and disadvantages of each.

This topic also applies to the Recipe question, specifically the procedure (mash procedure), and in some cases how the procedure is an important aspect of, at least tradionally, brewing specific styles


The primary goal of mashing is to achieve the sugar and protien profile required for the beer you are brewing which is acomplished with the breakdown of proteins and starches that was begun during the malting process. This is accomplished by several groups of enzymes that degrade different substrates (proteins and starches) during a series of rests at specific temperatures. Since most mashes are of the single infusion type and only include a sacrification rest (and maybe an optional mash-out) the mash has a large impact on the beers we brew by impacting the attenuation of the wort, again by manipulating its sugar profile.

Acid Rest

With pale lager malts, this enzymatic degradation begins with the acid rest, where phytase breaks down phytin into calcium- and magnesium-phosphate and phytic acid. This helps acidify the mash when the brewing water has a low calcium content and roasted grains are not part of the grist. This rest occurs at temperatures in the 95-120 F range. Another group of active enzyme in this range are the beta-glucanases, which break down hemicellulose and gums in the cell walls of undermodified malts. Some adjuncts, particularly rye, have high levels of these substances, and stuck mashes or other problems can result if they are not degraded to simpler substances by the beta-glucanases.

Protein Rest

For most malts, the mash begins with the protein rest, which is normally carried out at temperatures in the 113-127 F range. This process begins with the proteinases, which break down high molecular weight proteins into smaller fractions such as polypeptides. These polypeptides are further degraded by peptidase enzymes into peptides and amino acids, which are essential for proper yeast growth and development. Proteins of molecular weight 17,000 to 150,000 must be reduced to polypeptides of molecular weight 500-12,000 for good head formation, and some of these further reduced to the 400-1500 level for proper yeast nutrition.

Sacrification Rest(s) (Starch Conversion)

The final enzymatic process involves the conversion of starches into dextrins and fermentable sugars. The starches must be gelatinized for this to take place, and this occurs at temperatures of 130-150 F for barley malt. The gelatinization temperature is higher for raw grains, such as corn grits, so these adjuncts must be boiled or hot-flaked before adding to the mash. The breakdown of starches is carried out by the combined action of debranching, alpha-amylase and beta-amylase enzymes during the saccharification rest. Debranching enzymes break the 1-6 links in starches, reducing the average length and complexity of the molecules. The diastatic, or amylase, enzymes work in tandem, with the beta-fraction breaking off maltose units from reducing ends and the alpha-fraction breaking 1-4 links at random. Temperatures below 150 F favor beta-amylase, producing a more fermentable wort, while temperatures above 155 F favor alpha-amylase, producing a more dextrinous wort.

The simplest sugars produced in the manner are monosaccharides, with only one basic sugar structure in the molecule. Monosaccharides in wort include glucose, fructose, mannose and galactose. Disaccharides are made up of two monosaccharides coupled together, and include maltose, isomaltose, fructose, melibiose, and lactose. Trisaccharides (three monosaccharides) include maltotriose, which is slowly fermentable and sustains the yeast during lagering. One key characteristic of yeast is their ability to ferment Maltotriose. Many studies have indicated that this is the primary factor in attenuation. Maltotriose is a trisachride and the second most common sugar in wort (13-19% of fermentables). Most yeast can consume about half the Maltotriose present. Interestingly Lager yeast does a better job of utilizing Maltotriose than does Ale yeast. Oligosaccharides constructed of glucose chains (many monosaccharides joined together), are water soluble and called dextrins. The relative concentrations of these sugars are determined by the types of malt and whether the mash schedule favors alpha-amylase or beta-amylase activity.


After this phase is completed, many brewers mash-out by raising the temperature of the mash to 168 F and holding it there for several minutes. This ensures the deactivation of the amylase enzymes, halting the conversion of dextrins to fermentable sugars. It also reduces the viscosity of the wort, helping to make the lautering easier and more efficient. There is some controversy whether this step is necessary depending on the final mash temperature. However it is generally agreed that the best extraction rates are achieved when the mash is heated to this range.

1: Single Infusion Mash

This is the most common mash utilized today. it is implemented simply by mixing crushed grain and hot water to achieve the desired temperature within the sacrification range (typically 148-158F)
  • the malt is combined with hot water to reach a temperature appropriate for starch conversion.
  • It has the advantage of requiring a minimum of labor, equipment, energy and time,
  • It has the disadvantage of prohibiting the use of undermodified malt or adjuncts.

2: Step-infusion mash

This type of mash was developed to mimic the temperature rests of a decoction mash without requiring all the handling of the grains thus being simpler than a decoction.
  • The temperature is increased by external heat or the addition of boiling water.
  • allows a little more flexibility by moving the mash through a series of temperature rests
  • more resources than a simple infusion mash

3: Decoction Mash

Pilsner and pilsner imitations (From Pilsner Urquell to Bud), almost all german beers (some alts, Weizen, Rogenbeir), some of the lighter Belgian ales (De Koninck, Palm, Rodenbach) are traditionally decocted.
  • involves the removal of a thick fraction of the mash (usually one-third) and running it through a brief saccharification rest at a relatively high temperature. It is then boiled it for 15-30 minutes before mixing it back into the main mash. This is repeated as many as three times, depending on the modification of the malt and the beer style
  • The decoction helps explode starch granules and break down the protein matrix in undermodified malt, improving the extraction efficiency, and also promotes the formation of melanoidins. These compounds are formed from amino acids and reducing sugars in the presence of heat and are responsible for the rich flavors in malty lagers.
  • This mashing method is the most resource intensive, but is the traditional method for many lagers and some ales. A possible side-effect of the extended mash schedule is the extraction of higher levels of tannins and DMS precursors from the grain husks, though this is not significant at typical mash pH levels
  • Double Mash

    A fourth mashing method is the double mash, which can be viewed as a combination of infusion and decoction. As the name implies, it involves two separate mashes: a main mash consisting of crushed malt, and a cereal mash consisting of raw adjuncts and a small charge of crushed malt. The latter is boiled for at least an hour to gelatinize the starches and is then added to the main mash, which has undergone an acid rest. The mixture is then cycled through protein and saccharification rests using the step-infusion method. The double mash is the most common way of producing beer styles such as American light lagers that contain a high proportion of corn grits or rice.