Mashing! How? Why? To what extent?! Mashing is the brewer's term for the hot water steeping process which hydrates the barley, activates the malt enzymes, and converts the grain starches into fermentable sugars (alcohol) and unfermentable dextrins (body, mouthfeel, residual sweetness). Sugars Starch conversion is the most important aspect of mashing. In barley, starch makes up 63-65% of the dry weight. Starch is a polysaccharide (very large chains of glucose) which is insoluble in water. Brewers yeast, however, can only ferment monosaccharides (glucose), disaccharides (maltose) and trisaccharides (maltotriose - which can only be completely fermented by lager yeast strains). Starches found in malt are composed of amylose (a single chain of glucose molecules) and amylopectin (a branching chain of glucose molecules). In order for those starches to be converted into water-soluble sugars, they need to become gelatinized, and amylase enzymes need to break the long-chained starch molecules into shorter chains that can be further reduced by beta amylase to create simple sugars that can be consumed by yeast. Beta amylase produces maltose, the main sugar in wort, by splitting 2 glucose molecules from the end of an amylose glucose chain, but cannot get past the branch joins of amylopectin. Alpha amylase breaks down longer glucose chains, exposing additional ends for the beta amylase enzymes. Limit dextrinase is able to further split the links found in amylopectin, but it is more active at lower ph (5.1), and lower temperature (133 to 140), so only plays a minor role in most mashing schedules. Each of these enzyme groups is favored by different temperature and ph conditions. A brewer can adjust the mash temperature to favor each successive enzyme's function and thereby customize the wort to their taste and purpose.
Temperature Rests Acid rest (86-126), used to break down phosphates into compounds that would acidify the mash, allowing for conversion of starches where water sources were devoid of minerals (Pilzen, for example). No significant conversion takes place at this temperature. Can take several hours. Ferulic acid rest (109-113), primarily for the generation of ferulic acid, which wheat beer yeasts convert to 4VG (4-vinyl guaiacol), the banana and clove phenolic character that is the hallmark of Bavarian wheat beers. Protein rest (122-133), used on under- or moderately-modified malts to break down the endosperm. Can also be used to break up proteins that might cause chill haze, and improve head retention. Again, should only be used on moderatelymodified malts, or grists with a large proportion of unmalted grains. Otherwise, it will break up proteins responsible for body and head retention, leaving a thin, watery beer. Standard time is 20-30 minutes. Starch conversion / Saccharification rest (148-158, 153 on average), converts the starch reserves into dextrins and fermentable sugars. Alpha amylase (154-162) will break up long protein chains; beta amylase (131-150), will break up smaller chains. Mashing low (<150) produces a more fermentable wort (and a drier beer as a result), while mashing above 155 leaves a more dextrinous wort (fuller-bodied, sweeter). Usually the mash is held at this temperature for 60 to 90 minutes to ensure complete conversion of the starches. Temperature 140ºF (60ºC) 149ºF (65ºC) 160ºF (70ºC) 167ºF (75ºC) apparent limit of attenuation 87.5% 86.5 % 76.8% 54.0 % Mashing out (168), halts enzymatic activity and locks in the wort profile. Also serves to reduce the wort s viscosity, making lautering easier and more efficient.
Other considerations ph - Beta amylase works better in low ph, about 5.0. Alpha amylase likes a higher ph, about 5.7. But lower ph can leave unconverted pectins (haze) and a less-fermentable wort, and higher ph will yield more random distribution of variously complex sugars, as well as increase tannin extraction, leading to a harsh or astringent beer. A generally accepted ph threshold is 5.8-6.0. As a result, the mash ph is generally low enough to prevent excessive tannin extraction. A commonly accepted optimal range for mash ph is 5.2-5.7 with 5.5 being optimal for starch conversion activity. PH has effects beyond mash efficiency, including protein coagulation (clarity), hop utilization, maillard reactions (maltiness, melanoidin formation), yeast health, beer stability (resistance to spoilage), and beer flavor. Time - Generally 60 to 90 minutes, though some experiments have shown good conversion in as little as 15 minutes. Grist/water ratio - A thinner mash (>2 quarts of water per pound of grain) dilutes the concentration of enzymes, slowing conversion, but yields a more fermentable mash since the enzymes are not inhibited by a higher concentration of sugars. A thicker mash (<1.25 quarts per pound) is better for protein breakdown, and results in faster conversion, but is less fermentable and will yield a sweeter, maltier beer. Grain crush - A finer crush allows freer access to the starches that will be converted to sugars, increasing extract efficiency, but can lead to tannin extraction (debatable) and stuck or slow sparges. Putting it all together, on average: 1.5 qts/ppg, ph of 5.3, temperature of 150-155 for one hour should yield a wort with a nice balance of body and fermentability that works well for British and American style ales. Methods of mashing Infusion mashing All the crushed malt is mixed with hot water to achieve a mash of the desired temperature. Strike water temperature will vary based on the desired thickness of the mash and other factors, but will generally be about 10-15 degrees above the desired mash temperature. The temperature of the strike water can be calculated as: Strike Water Temperature Tw = (.2/R)(T2 - T1) + T2 R = Ratio of water to grain in quarts per pound T1 = the temperature of the grains in Fahrenheit (or Celsius) T2 = the target temperature of the mash in Fahrenheit (or Celsius)
Single temperature infusion mash This method uses a single temperature rest at which the beta and alpha amylase enzymes are active to convert the malt starches into wort sugars. This is the most common mash schedule for homebrewers, and is well-suited to malts which have been highly modified. It also pairs well with unheated mash tuns (such as converted coolers), which are common amongst homebrewers. Multi step infusion mashes Mashes with more than one temperature rest (not counting a mash-out rest, if used). A popular multi-rest schedule hits 104, 133, and 158 degrees (doughing-in, protein rest, and saccharification rest) for a half hour at each temperature. This mash schedule provides high yields and produces good fermentability. This is better for less well-modified malts (German Pilsener), and will produce a maltier-tasting beer. Unless using a direct-fired mash tun, infusions of boiling water are added to raise the temperature between mash steps. To calculate the amount of water to add, and at what temperature: Wa = (T2 - T1)(0.2G + Wm)/(Tw - T2) Wa = The amount of infusion water added Wm = The total amount of water in the mash T1 = The initial mash temperature T2 = The target mash temperature Tw = the actual temperature of the infusion water G = The amount of grain in the mash Decoction mashing This is a method of conducting multi-rest mashes without adding additional water or directly heating the mash tun. It refers to removing a part of the mash, raising its temperature 2-4 degrees per minute (with a 15 minute rest at 155-162), boiling it for 5 to 45 minutes (shorter for light-colored beers, longer for darker beers), and returning it to the main mash to raise its temperature to the next rest step. The decoction (the portion removed from the main mash and being boiled) may require stirring to avoid scorching the grain. The process of boiling gelatinizes the starches and makes them more accessible to the enzymes, though it does inactivate the enzymes in the decocted portion of the mash. The decoction is typically done two or three times, depending on the number of mash rests. The triple decoction is how the first Pilsners were brewed, and how many German beers are still brewed. It employs 3 main temperature rests: acid rest, protein rest, and saccharification rest. To calculate the decoction volume: decoction volume = total mash volume * (target temp - start temp) / (boil temp - start temp)
and add about 15-20%. This way, the brewer can decoct more mash than necessary, and add it back slowly to the main mash while constantly checking temperature. When the rest step is reached, the rest of the decoction is allowed to cool until it s close to the desired mash temperature, and only then added back in. It is preferable to leave most of the liquid in the main mash tun, but the grains in the decoction should still be submerged in liquid. Cereal mashing This is a method of combining two separate mashes, typically one consisting of crushed malt, and the other comprised of raw adjunct grains (corn grits, rice, unmalted wheat) and a handful of crushed malt (for its diastatic power). The cereal mash is boiled for an hour or more to gelatinize the starches, which helps to avoid the dreaded stuck sparge. This is then added to the main mash, which has undergone acid and/or protein rests, and raises the overall temperature into the saccharification range (otherwise, heat or boiling water needs to be added to get it to the correct temperature). Reiterated mashing Mashing a second (or third, or fourth, or ) grist using the wort from the previous mash as the strike water. Parti-gyle brewing Creating multiple beers from the same mash. After running off the wort from the mash, add in a bit more crushed grain and mash again for a second, smaller (table) beer. Sources: How to Brew Brulosophy Beersmith BJCP Braukaiser