Ctt

Figure 1. Mesopotamian clay tablet. Source: Courtesy of the Beer Institute.

or multiples of the fermenter size. Aging tanks, preassem-bled on site, are shown in Figure 4.

Each stage offers the brewery many choices. It is for these reasons that there are not many beers, perhaps none, that are exactly alike. The finished beer may be packed in large containers, holding 2-31 gal, or into small ones, holding 7-40 oz.

RAW MATERIALS OF BREWING Water

Water is, only quantitatively, the major component of beer. Its requirements for brewing are fairly simple. First, it must meet local or international standards for potable water. The World Health Organization's standards for drinking water are shown in Table 1.

The second requirement is that it not be too alkaline. A maximum alkalinity of 50 ppm (as calcium carbonate) is acceptable.

A third requirement is that it be hard and contain calcium. The level of calcium considered most desirable is 100 ppm (as calcium), but lesser amounts may also be used. The water in Pilsner, Czechoslovakia, had these attributes, neutrality and hardness, and soon became the standard by which all beer is made.

All water supplies are either surface water or groundwater. Surface water is derived from rainfall or snow and may be quite pure. If it is collected in reservoirs near the source of rain or snow, it is usually soft and neutral. If it is collected in rivers, its purity will depend on the distance between the collection and distribution points and the uses f f

Figure 4. Aging tanks assembled on site. Source: Courtesy of Paul Mueller Company.

Table 1. World Health Organization Standards for Drinking Water

Maximum permissible concentrations (mg/L)

Chlorides 60

Sulfates 400

Calcium 200

Magnesium 150

Total dissolved solids 1,500

it suffers in between. Such water may need purification with sand and charcoal.

Groundwater comes from wells or springs and is usually tasteless but may be quite alkaline or hard, or both. Such water may need acidification to remove alkalinity and, less often, softening if it is too hard. Such water rarely needs treatment with activated charcoal.

Barley Malt

Malted barley is the principal ingredient of beer. It furnishes almost all the required elements for making beer. Malt provides starch and sugars, which will, partly or completely, become alcohol during fermentation; and protein and amino acids, which will supply nutrition for the yeast, as well as color, foam, and flavor in the finished beer.

Barley used to make malt is almost always selected from special strains that have been developed and grown specifically for this purpose. There are two major types of barley, distinguished by the number of rows on the stalk. Six-rowed barley is grown mainly in the midwest of the United States and Canada, but now also in Europe and Australia. Two-rowed barely is grown in the far west, and also in Europe and other barley growing regions. The two-rowed barleys are considered by some to give a smoother beer. A drawing of a barley kernel is shown in Figure 5.

The husk, which protects the seed and is composed of the palea and lemma, is, in barley, alone among the cereals, fused to the testa and the pericarp. It is this fusion that permits barley to be malted efficiently and to be the universal basis for making beer. Grains that lose their husks at germination tend to become moldy when malted in bulk.

The malting of barley begins with steeping, in which the barley, in tanks, is soaked in aerated water. The steeped water is changed several times. The steeping is complete when the barley reaches a moisture content of 45%. It is then transferred to long, horizontal compartments, through which moist air is blown. In 4-6 d, the barley germinates and starts to grow as if it were to become a barley plant. During this time the barley produces starch-splitting enzymes, notably a-amylase and /?-amylase, and also proteinases and cellulases. The amylases break down some of the starch in the barley; the proteinases degrade some of the proteins to amino acids, and the cellulases soften the cell walls. All these enzymes are secreted by the aleurone layer and migrate into the endosperm. These changes, which collectively are called modification, prepare the barley for its use in brewing.

At the time when the modification is considered complete, the malt is transferred to a kiln and dried. The temperature at which the malt is dried determines the color and, partly, the flavor of the beer from which it will be made. Kilning stabilizes the malt and allows it to be shipped widely and to be stored for a year or more.

The analysis of a typical malt is shown in Table 2.

UNMALTED CEREALS (ADJUNCTS)

Cereals such as rice, corn, and sorghum are often used to complement or attenuate the malt. These grains do not

Dorsal side

Aleurone layer

Lemma Pericarp jes^a

Embryo

Acrospire

Scutellum Rootlets Coleorhiza

Aleurone layer

Lemma Pericarp jes^a

Acrospire

Micropylar region

Endosperm

Sub-aleurone region

Palea

Crushed cell layer

Endosperm

Micropylar region

Sub-aleurone region

Palea

Figure 5. Schematic longitudinal section of a barley grain, taken to one side of the furrow, showing the disposition of the parts.

Crushed cell layer

Ventral furrow side

Broken Scutellar pedicel epithelium

Proximal end

Table 2. Analysis of Barley Malt (%)

Moisture 4.0

Starch and dextrins 52.5

Simple sugars 9.5

Total protein 13.0

Soluble protein 5.4

Cellulose 6.0

Other fiber 10.0

Fats 2.5

Minerals 2.5

contribute to flavor, color, or foam but serve only to supply carbohydrates to the wort. Their use probably arose when malt was in short supply. They are widely used throughout the world. Only in parts of Germany, in Switzerland, and in Greece is their use prohibited by law. This prohibition, which dates to 1516 in Bavaria, as the Reinheitsgebot, originally was intended as a means to police the taxation of beer because malt could only be made in a malthouse. The prohibition on the use of other sources of carbohydrates precluded the surreptitious increase in beer production. It remains to this day as a vestigial reminder of days past that has served to prevent the importation into those three countries of beers made with unmalted cereals. However, the European Common Market has overruled this law and such beers may now be imported into the all-malt countries.

The quantity of unmalted cereals may vary from 10 to 50% of the total mash, depending on the beer to be produced. Increased use gives a lighter, less bodied beer. If rice or sorghum is used, it must be ground before mashing. If corn is chosen, then a physically separated fraction of the ground corn kernel that contains mainly starch and protein and very little corn oil is used.

Starch is the major component of both malt and the other cereals. It is a complex polysaccharide made up of about 35% of a straight-chain polymer of glucose known as amylose and about 65% of a branched polymer, amylopec-tin. The links in all of amylose are 1,4' bonds between neighboring glucose units. The bonds in amylopectin are both 1,4' and 1,6',—the latter at the branch points. Schematic diagrams of amylose and amylopectin are shown in Figure 6 and 7, respectively.

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