Figure 9-4. Types of malt used in brewing. Shown (from left to right) are four types of malt, ranging from light to dark. These malts are used to make beers with similar colors. Figure courtesy of Rich Chapin (Empyrean Ales, Lincoln, Nebraska) and John Rupnow (University of Nebraska).
products ranging from a very fine to very coarse grind.
Prior to milling, the malt is surrounded by a tough husk, which separates from the grain during milling, but generally is only partially degraded. The fineness of the malt and the extent of husk degradation are extremely important and depend on the preference of the brewer.The finer the malt, the more easily enzymes and other materials are subsequently extracted during the next step, the mashing phase. However, the insoluble residue remaining after mashing is difficult to separate, due to its small particle size. In contrast, the spent malt material is more easily separated from the mixture if coarse malt, with minimum husk damage, is used. In other words, extraction of enzymes, starches, protein, nutrients, and flavors is greater with finely milled malts, but the filtration rates are slow. Conversely, good filtration rates but poor extraction occurs with coarsely milled malts.
Finally,the ground malt or "grist"is ready to be used in the step called mashing.The purpose of mashing is two-fold. First, the enzymes, starches, proteins, and other substances are extracted and solubilized in a hot aqueous solution. Second, the extracted enzymes, starches, and proteins react to form products that ultimately serve as substrates to support growth of yeasts during the fermentation phase. The precise steps involved in mashing—in particular, the composition of the water, the temperature, and the heating rate—are critical factors, subject to the preferences of the individual brewer.
Mashing begins when the malt is mixed with brewing water (usually at ambient temperature) in a specialized tank called a "mash tun." About 20% to 30% malt is usually added. Water quality has a profound influence on the quality of the beer (it is, after all, the main ingredient), thus geographical considerations can be very important.
The reputations of many beers are based, in part, on the source, location, and properties of the water used to make the beer. For example, the famous Pilsener beers were made from the very soft water in the Pilsen region of the
Czech Republic, whereas the great English-style pale ales developed in Burton-on-Trent in England, where the relatively hard water is high in minerals and bicarbonate.And although many beer manufacturers continue even today to make quality claims (and television commercials) based on the water from which the beer is made, others argue that by making adjustments for mineral content, pH, and ionicity, water variability is much less a factor in determining beer quality.
In general, brewing water should have medium hardness, containing about 100 ppm each of calcium and magnesium salts and 50 ppm or less of bicarbonate/carbonate.The pH should be between 6 and 7.The specific functions of these components are described in Table 9-2.
The malt-water mixture, or mash, is gradually heated from 20°C to 60°C to 65°C by infusion, decoction, or a combination of the two. Infusion heating is a simple step-wise process in which the mash is heated to an incremental temperature, held for a period of time, then the temperature is raised again, held, and so on until the final temperature is reached.
In decoction heating, a portion of the mash is separated and boiled in a separate kettle, then added back to the main mash, thereby raising the combined mash temperature. The main advantage of decoction mashing is an increase in starch extraction. Decoction mashing is used mainly for lager beers; in the United States a combination of infusion and decoction heating is most common.
One might ask why the heating process during mashing is done in a particular order, rather than simply heating the mash to some given temperature and then holding it there for a pre-determined time. Remember that the purpose of mashing is to extract and react. In reality, there are many enzymes in the malt, not just a single amylase or a single proteinase. Likewise, there are many sugar-containing polymers and starches with varying degree of branching, as well as heterogenous proteins, that will eventually serve as substrates. Pigments, flavors, and other substances are also
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