Editing Mashing (section)

==Enzymatic rests==
{| border=1 align=right class=wikitable |
|+ <small>Optimal rest temperatures for major mashing enzymes</small>
! Temp °C !! Temp °F !! Enzyme !! Breaks down 
|-
| 40–45&nbsp;°C || 104.0–113.0&nbsp;°F || β-Glucanase || β-Glucan
|-
| 50–54&nbsp;°C || 122.0–129.2&nbsp;°F || Protease || Protein
|-
| 62–67&nbsp;°C || 143.6–152.6&nbsp;°F || β-Amylase || Starch
|-
| 71–72&nbsp;°C || 159.8–161.6&nbsp;°F || α-Amylase || Starch
|}
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 [[Denaturation (biochemistry)|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&nbsp;°C per minute, enzymes may be prematurely denatured in the transition layer near the heating elements.

===β-Glucanase rest===
[[beta-glucan|β-glucan]] is a general term for [[polysaccharides]], such as [[cellulose]], made up of chains of [[glucose]] molecules connected by beta [[glycosidic bond]]s, as opposed to the alpha [[glycosidic bond]]s in starch. They are a major constituent of the [[cell wall]]s of plants and make up a large part of the [[bran]] in grains. A '''β-glucanase rest''' done at {{convert|40|°C|°F|0|abbr=on}} 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]] 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]] 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 [[dextrin]]s or [[maltodextrins]], 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&nbsp;°C) and β-amylase (55-65&nbsp;°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. {{convert|66|°C|°F|0|abbr=on}} is a typical rest temperature for a [[pale ale]] or German [[pilsener]], while Bohemian pilsener and [[mild ale]] are typically rested at {{convert|67|-|68|°C|°F|0|abbr=on}}.

===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.