What is Mashing?
The following is an excerpt from my book, "How to Brew Your First Beer - Extract or All-Grain", due to be published sometime in 1996. This text is copyrighted, and may be copied and reproduced for personal use but may not be reproduced for sale or publication. All Rights Reserved by New Wine Press, 1996.
**Blah, blah,blah......I shortened this whole article down to the basics of grain and mashing. This guy probably never even finished a book! MW
*The Acid Rest and Modification
*The Protein Rest
*The Starch Conversion/Saccharification Rest
*Manipulating the Starch Conversion Rest
*How pH Affects the Mash
*Water Chemistry Primer
Mashing is the brewers term for the process of malt enzyme activation and subsequent conversion of the grain starches into fermentable sugars. There are several different enzymes that take part in the overall conversion of the grain starches to sugars. When mashing malted grain, the brewer is concerned with two main classes of enzymes: proteases (or
proteolytic enzymes), and diastases (or diastatic enzymes). Proteolytic enzymes break down long complex chains of protein molecules into simple proteins and amino acids. Diastatic enzymes convert starch molecules into fermentable sugars and unfermentable dextrins. Each of these enzymes are favored by different temperature and pH conditions. A homebrewer can adjust his or her mash temperature to favor each successive enzymes function.
The starches in the mash are about 90% soluble at 130 ¡F and are not completely soluble until the temperature reaches 149¡F. Unmalted grains have their starch reserves locked in a protein matrix which prevents enzyme conversion. Only by crushing or rolling the grains under heat is the matrix broken up. The starches can be gelatinized by heat alone or by a combination of heat and enzyme action. Either way, a mash is needed to convert the soluble starches to fermentable sugars.
Figure 11 - Nominal Enzyme Ranges in the Mash
Table 5 - Major Enzyme Groups and Functions
Enzyme Temperature Range Optimum pH RangeFunction
Phytase 86 - 126¡ F4.4 -5.5 Lowers the Mash pH. No longer used.
Beta Glucanase 98 - 113¡ F4.5 - 5.0 Best gum breaking rest.
Peptidase 115 - 135¡ F4.6 - 5.2 Produces Free Amino Nitrogen
Protease 115 - 135¡ F4.6 - 5.2 Breaks up large proteins that form haze.
Beta Amylase 130 - 150¡ F5.0 - 5.6 Produces small, highly fermentable sugars.
Alpha Amylase 155 - 167¡ F5.3 - 5.8 Produces larger, less fermentable sugars.
Note: The above numbers were averaged from several sources and should be interpreted as nominal optimum activity ranges. The enzymes will be active outside the indicated ranges but willbe denatured as the temperature increases above each range.
The Acid Rest
The first of these enzymes is phytase and it is active at temperatures of 86 - 126 ¡F. Phytases function is to lower the mash pH when the brewing water is very low in minerals. Pale lager malt is rich in phytin, an organic phosphate containing calcium and magnesium. Phytase breaks down phytin into insoluble calcium and magnesium phosphates and
phytic acid. The process lowers the pH by removing the ion buffers and producing this weak acid. This stage is known as the Acid Rest but it is not often used nowadays. It can take several hours for this enzyme to lower the mash pH to the desired 5.0 - 5.5 range. Additionally, most base malts in use today are more fully "Modified" which essentially removes the phytin for the enzyme to act upon.
This temperature range is also used for "Doughing In", mixing the grist in with the water to allow time for the mash to liquify and time for the enzymes to be distributed. The use of the a 20 minute rest at these temperatures has been shown to be very beneficial to improving the yield from all enzymatic malts, even fully-modified ones. This step is considered to be optional but can improve the yield by a couple of points per pound.
The Protein Rest and Modification
Modification is a term which describes the degree of breakdown of the protein-starch matrix (endosperm) that comprises the bulk of the seed. Moderately-modified malts need the Protein Rest to help release the enzymes that are responsible for breaking down the large proteins into amino acids and releasing the starches from the endosperm. Fully-modified malts have already produced these enzymes and do not benefit from more time spent in Protein Rest regime. Most base malt in North America is fully modified. Brewers have reported fuller, maltier flavors from malts that are less modified and make use of this rest. Less modified malts are usually available from German maltsters and are evident in the beers produced there.
Malted barley also contains a lot of amino acid chains which form the simple proteins needed by the germinating plant. In brewing, these proteins are instead utilized by the yeast for their growth and development. The two main proteolytic enzymes responsible are peptidase and protease. Peptidase works to provide the wort with amino acid nutrients that will be used by the yeast. There is usually more than enough nutrients in a typical all-grain wort without making use of this enzyme, however. Protease works to break up the larger proteins which enhances the head retention of beer and reduces haze.
The temperature and pH ranges for these enzymes overlap. The optimum pH range is 4.6 - 5.2 and both enzymes are active enough between 115 - 135¡F that talking about an optimum range for each is not relevant. This optimum pH range is a bit low with respect to most mashes, but the typical mash pH of 5.3 is not too far out of the ballpark. There is no
need to attempt to lower the mash pH to facilitate the use of these enzymes. The typical Protein Rest at 125 - 130¡F is used to break up the proteins which might otherwise manifest as Chill Haze and improve the head retention in lightly kilned and/or less-modified malts. The standard time for a protein rest is 20 - 30 minutes. Too long in the
protein rest, and the proteins responsible for Head retention and body will be diminished. This rest should primarily be used when using moderately-modified barley malts, wheat, rye, or oatmeal. Otherwise there is usually no need with today's fully-modified malts.
The other protein enzyme in this regime is used to break up the beta glucans in (un)malted wheat, oatmeal and unmalted barley. These glucan carbohydrates are responsible for the gumminess of dough and if not broken down will cause the mash to turn into a solid loaf ready for baking. Fortunately, the optimum temperature range for the Beta
Glucanase enzyme is below that for the proteolytics. This allows the brewer to rest the mash at 98 -113¡F for 20 minutes to break down the gums without affecting the proteins responsible for head retention. The use of this rest is really only necessary for brewers incorporating a large amount (>50%) of wheat, rye or oatmeal into the mash. Sticky mashes and lauters from lesser amounts can usually be handled by increasing the temperature at lautering time (Mashout).
Starch Conversion / Saccharification Rest
In this stage the diastatic enzymes start acting on the starches, breaking them up into sugars (hence the term saccharification). One group, the amylases, are enzymes that work on the more complex starches and sugars. The two main amylases are Alpha and Beta. Alpha works by breaking up long sugar chains, while Beta just nips off the ends making lots of highly fermentable simple sugars.
The temperature most often quoted for mashing is about 153¡F. This is a compromise between the two temperatures that the two enzymes favor. Alpha works best at 158F, while Beta is deactivated at that temperature, working best at 140F. Alpha amylase also works to aid liquification of the mash (i.e. aiding starch solubility) at temperatures around 120¡F.
The brewer can use iodine (or iodophor) to check a sample of the wort to see whether the starches have been completely converted to sugars. As you may remember from high school chemistry, iodine causes starch to turn black. The mash enzymes should convert all of the starches, resulting in no color change when a couple drops of iodine are added. The iodine will only add a slight tan or reddish color as opposed to the flash of heavy black color if starch is present. Worts high in dextrins will yield a reddish color when iodine is added.
What do these two enzymes and temperatures mean to the brewer? The practical application of this knowledge allows the brewer to tailor the wort in terms of its fermentability. A lower mash temperature, e.g. 150F, yields a thinner bodied, drier beer. A higher mash temperature, e.g. 159F, yields a less fermentable, sweeter beer. This is where a brewer can really tailor a wort to best produce a particular style of beer.
Manipulating the Starch Conversion Rest
There are two other factors besides temperature that also effect the amylase enzyme activity. These are wort viscosity and pH. Beta amylase is favored by a low wort pH, about 5.4. Alpha is favored by a higher pH, about 5.7. However, a Beta-optimum wort is not a very fermentable wort, Alpha amylase is needed to break up the larger chains so Beta can work on them. A good analogy is to visualize building a fire from a stand of oak trees. If you picture Alpha as being a big chainsaw and Beta being a small hatchet, you can understand that using both tools to make the best use of the wood will make the best fire.
Adjusting the pH during the mash through the use of calcium carbonate aka. chalk (to raise) or calcium sulfate aka. gypsum (to lower) can only be carried so far before the addition of these salts affects the wort flavor. Water treatment is an involved topic and is discussed in several books in the Recommended Reading section. For the beginning masher, it
is often better to let the pH do what it will and work the other variables around it. The malt selection can do as much or more to influence the pH as using salts in many situations. The pH of the Mash or wort runnings can be checked with pH test papers sold at Brewshops, and Pool Supply stores.
Wort Viscosity is another factor influencing the performance of the mash. A thinner mash of >2 quarts of water per pound of grain dilutes the relative concentration of the enzymes, slowing the conversion, but ultimately leads to a more fermentable mash because the enzymes are not inhibited by a high concentration of sugars. A stiff mash of <1.25 quarts of water per pound results in a faster overall starch conversion but the resultant sugars are less fermentable and will result in a sweeter, maltier beer. A more viscous mash is also more protective to the enzymes. The enzymes are not deactivated as quickly by a rise in temperature, which is good for multirest mashes. A common mash water/grist ratio is 1.5 quarts per pound.
As always, time changes everything; it is the final factor in the mash. Starch conversion can complete in only 30 minutes, so during the remainder of a 60 minute mash, the brewer is working the mash conditions to produce a desired profile of wort sugars. Depending on the factors of pH, viscosity and temperature, the time required to complete the mash can vary from the intial 30 minutes to 90. At a higher temperature, a stiffer mash and a higher pH, the alpha amylase is favored and starch conversion will be complete in 30 minutes. Longer times at these conditions will allow the beta amylase time to breakdown more of the longer sugars into shorter ones, resulting in a more fermentable wort, but these Alpha-favoring conditions are deactivating the Beta; it is self-limiting. A compromise of all factors yields the standard mash conditions for most homebrewers: a wort viscosity of about 1.5 quarts of water per pound grain, pH of 5.3, temperature of 153-155F and a time of about one hour. These conditions yield a wort with a nice maltiness and good fermentability.
The dark, roasted malts can really influence the pH of the beer. These highly roasted malts react with the minerals in the water to lower the water's pH. The chemistry of the water determines the degree of the effect that the malt has. The best way to explain this is to describe two of the world's most famous beers and their brewing waters. The Pilsen region of the Czech Republic was the birthplace of the Pilsener style of beer. A Pils is a crisp, golden clear lager with a very clean hoppy taste. The water of Pilsen is very soft, free of most minerals and low in carbonates. Using an Acid Rest with this water allowed the pale lager malts to easily bring the pH down to the target mash range of 5 - 5.5.
The other style in question is the Stouts of Ireland. The water of Ireland and the British Isles is fairly high in carbonates (CO3--), which adds a large degree of buffering power and makes the water harder and more alkaline. The higher pH of this region makes it difficult to produce light pale beers. The water does not allow the pH of the Mash to
hit the target range of 5 - 5.5, it remains higher and this produces conditions whereby the harsh phenolic and tannin compounds can be extracted from the grain husks. The lower pH of an optimum mash (5.3) normally prevents these compounds from becoming soluble. This region is world renowned for producing outstanding dark beers though. The reason is the dark malt itself. The highly roasted black malts and the dark crystal malts used for stout add acidity to the mash. These malts match and counter the buffering capability of the carbonates in the water, lowering the mash pH to the target range.
On the other hand, dark beer cannot be brewed in Pilsen without adding the buffering salts. Without the carbonates, the mash would become too acidic and the dark beers would take on a harsh tone. Homebrewers should get a water analysis from their local water supplier and look at the mineral profile to establish which styles of beer can best be produced from their water. The use of darker malts such as Chocolate, Black Patent, Dark Crystal, and the toasted malts such as Munich and Vienna, can be used successfully in areas where the water is alkaline, i.e., a pH greater than 7.5 and a carbonate level of more than 200 parts per million, to produce good mash conditions. If you live in an area where the water is very soft (like Pilsen), then you can add brewing salts to the mash and sparge water to help achieve the target pH.
Confused? Lets start a little simpler.