Grain: Malting and Mashing This is a brief primer on grains, especially barley. Grains provide sugar, flavors, color, and protein and other yeast nutrients. Malting and mashing are really part of the same process of converting the long biological polymers in the grain into useful subunits and extracting these from the grain. Pages 16-20 in MABS show the barley kernal and some of its anatomical features. See also the sample. The Endosperm contains the starch grains in a protein matrix. Glassy, steely endosperm is rich in protein, hence bad for brewing. Good barley has a white endo sperm. Most of the interesting enzymes are in the sub-aleurone layer, especially after malting. These enzymes are produced in the aleurone layer. The embryo resides at one end of the kernal and includes the acrospire. The processing of barley starts with malting. During malting, barley (or other grain) is steeped in water for a few days, depending on many factors, until the desired moisture content is reached. The grain is then spread thinly on a floor and germination is allowed to proceed with regular turning of the grain. Durin g germination enzymes that will breakdown the starch and protein of the kernal are produced and/or activated. These begin to work on the kernal and the acrospi re begins to grow across the lenght of the kernal. The effect of this process is known as modification. Complex starch is simplified (see below) and some protein is degraded. The extent of modification can be tracked by monitoring the growth of the acrospire (by examination of a kernal split lengthwise) and whether the end of the kernal away from the embryo is still steely or if it has softened and turned white (by observation and by chewing). When the desired degree of m odification has been obtained, the barley is roasted. In general continental European malts are known to be less modified than UK or US malts, with UK malts being the most modified. The less modified malts may give better malt flavor but are harder to use (see below). US malts, especially 6-row have the highest enzymatic power but also high protein levels that can lead to chill hazes. Barley malt may be broken down into three categories: Pale (enzymatic), Dark (enzymatic) and Specialty (not enzymatic). The enzymatic power refers to the ability of a malt to break down starch. This power is also called diastatic power and is measured in degrees Lintner. Malts range from 0-200 degrees Lintner, with a rule of thumb being that the average degree Lintner over all the starch in the mash must be >30. Pale malts are produced by light roasting (175F). Alpha and beta amylase and protease enzymes are retained well here. This includes pale ale and lager malt. These are used to provide the bulk of the sugar and for their ability to convert starchy adjuncts in the mash. The darker enzymatic malts are roasted (kilned) at 200-300F. Only a little enzymatic power is retained in these malts which include Vienna, Munich, amber, brown, etc. These are used in certain continental beer styles to contribute malty flavors, but they cannot break down adjuncts. The dark specialty malts, chocolate and black patent are essentially re-roasted pale malt. Temperatures of up to 450F are used and all enzymatic power is lost. Roasted barley is similar to these except that it is not malted beforehand. These malts are used for their flavor and color in stouts, porters, etc. The other type of specialty malt is crystal. This is a fully modified malt that is resteeped at 150-170F for 1.5-2 hours with minimal ventilation. This is essentially mashing within the kernal (see below). The high concentration favors amylolysis over proteolysis and allows the use of the high temperature. The malt is then roasted at 250F until the desired color is reached. The roasting of the sugary kernal, if allowed to proceed to the 40 lovibond mark or beyond (Lovibond measures grain and wort color, see below) produces caramel flavors that persist to the finished beer. These malts have no enzymatic power, but need none as they are fully converted. Crystal malts (including cara-pils, -vienna, and -munich) add flavors, colors, and residual sweetness to beer. In mashing the protein and starch breakdown continues. The preceeding table (same as the table I gave in the extraction article) gives the amount of sugar that might be obtained from the various grains (and other adjuncts). The units are the increase in specific gravity points (thousandths) from 1 pound of grain in 1 gallon of water. Note that most people will only get 80-90% of these values. Formulae can be used to calculate the expected OG and color of a wort from the numbers on this table and from knowledge of the brewer's system. How is all this done?: Mashing The barley is crushed or cracked. Ideally the husk is removed whole as it contains tannins that cause astringency and chill haze in the finished beer. The finer the endosperm is crushed, the more easily it will be wetted and converted. Water is added. The mash may be held at from 1 to several temperatures in an effort to control the balance of the various products and to compensate for the type (degree of modification and diastatic power) of grains used. There are three basic types of mash: simple infusion, temperature programming, and decoction. To understand why these work we must understand the enzymes that are in the malt. Amylases break down starch to sugar. There are two types of starch, amylose and amylopectin. (See pg 29, BoMaB.) The former stains black with iodine and the latter stains red. The latter is mostly degraded in well modified malt. Neither of these enzymes can break amylopectin at its branch points. Alpha amylase cleaves the chains randomly in the middle, producing in general smaller but still unfermentable sugars. The most favorable temperature for this enzyme is 154-162 F. Beta amylase cleaves a disacharide, maltose, from the end. This is the main fermentable wort sugar. This enzyme works best at 140-148F. (These temperatures are really the temperatures just below which the enzymes are destroyed by heat at a high rate.) The fermentability of the wort, and hence the sweetness of the beer, is controlled in mashing by controlling the relative action of these two enzymes. Purified unfermentable sugars (lactose, maltodextrin) may be added to the boil to boost residual sweetness. Proteases break down protein. The fundamental unit of protein, the amino acid, is an important yeast nutrient so some protein breakdown is require for this. Also head retention relies on the presence of medium-sized proteins, so some but not too much proteolysis helps head retention. In well modified malt there has already been sufficient proteolysis for good head retention and this should be avoided in the mash. Large proteins are irrelevant as they are precipitated in the boil. Proteases work at 113-136F. In the simple infusion mash water and malt are mixed at about 155F and this temperature is held until conversion is complete, as tested by iodine or other methods. This is the traditional UK system and works for their well modified grain since no protein rest is needed. In the temperature program mash the mash is held at several temperatures, each higher than the last. The specific enzymes are thus used to the extent desired. This is advantageous for less modified malt and mashes high in nonenzymatic adjuncts. Temperature is raised by the application of heat to the mash. In decoction mashing temperature rests are also used but the temp is increased by withdrawing part of the mash, boiling this, and returning it to the bulk of the mash. This has the advantage of solubilizing some adjuncts' hard-to-solubilize starch, but the disadvantage of deactivating some enzymes. This is a traditional continental technique, good for poorly modified grain, and especially for adjuncts like wheat which may be difficult to solubilize. Very time consuming. Once the mash is complete the wort must be separated from the spent grain. This is lautering. Basically the wort is strained out while clean water (hot liquor) is used to wash any sugars from the grain (sparging). While simple in concept this is a problem for many homebrewers. Oversparging, high temp or high pH hot liquor can release tannins from the grain. As mentioned above, these contribute to astringency and can complex with proteins to form chill haze.