| MALTING | | | | Flavouring Value of Hops |
| Balley Conversion | | | | Several varieties of the hop (Humulus lupulus) are |
| In order to be fermented by yeast, the food | | | | selected and bred for the bitter and aromatic qualities |
| reserve of barley, starch must be converted by | | | | that they lend to brewing. The female flowers, or |
| enzymes into simple sugars. Two enzymes, a- and b- | | | | cones, produce tiny glands that contain the chemicals |
| amylases, carry out the conversion. The latter is | | | | of value in brewing. Humulones are the chemical |
| present in barley - but the former is made only during | | | | constituents extracted during wort boiling. One |
| germination of the grain. | | | | fraction of these, the a-acids, is isomerized by heat |
| Steeping | | | | to form the related iso-aacids, which are responsible |
| Malting begins by immersing barley harvested at less | | | | for the characteristic bitter flavour of beer. |
| than 12 percent moisture in water at 120 to 150C | | | | Traditionally the dried hop cones are added whole to |
| (550 + 600) for 40 to 50 hours. During this steeping | | | | the boiling wort, but powedered compressed hops |
| period, the barley may be drained and given air rests, | | | | are often used because they are more efficiently |
| or the steep may be forcibly aerated. As the grain | | | | extracted. In addition, the hop components may be |
| imbibes water, its volume increases by about 25 | | | | extracted by solvents such as liquid carbondioxide |
| percent, and its moisture content reaches about 45 | | | | and added in this form to the wort or after |
| percents. A white roots heath, called a chit, breaks | | | | isomerization, to the finished beer. |
| through the husk, and the chitted barley is then | | | | Heating and Cooling |
| removed from the steep for germination. | | | | The kettle boil lasts 60 to 90 minutes, sterilizing the |
| Germination | | | | wort, evaporating, undesirable aromas, and |
| Activated by water and oxygen, the root embryo of | | | | precipitating insoluble proteins. Trub and spent hops |
| the barley corn secretes a plant hormone called | | | | are then removed in a separator where the hop |
| gibberellic acid, which initiates the synthesis of a- | | | | cones form the filter bed. In modern practice a more |
| amylase. The a- and b- amylases then convert the | | | | rapid whirl pool separator is also used. This devise is a |
| starch molecules of the corn into sugars that the | | | | cylindrical vessel into which wort is pumped at a |
| embryo can use as food. Other enzymes, such as | | | | tangent, the circulating whirlpool movement causing |
| the proteases and b- glucanases, attack the cell wall | | | | solids to form a cone at the bottom. Clarified wort is |
| around the starch grains, converting insoluble proteins | | | | cooled, formerly in shallow troughs or by trickling |
| and complex sugars (called glucans) into soluble amino | | | | down an inclined. Cooled plate but now in a plate heat |
| acids and glucose. | | | | exchanger. This last is an enclosed, hygienic vessel in |
| Kilning | | | | which hot wort runs along plates while cold water |
| Green malt is dried to remove most of the moisture, | | | | passes along the other side in the opposite direction. |
| leaving 5 percent in lager and 2 percent in traditional | | | | Oxygen is added at this stage, and the cooled wort |
| ale malts. This process arrests enzyme activity but | | | | passes to fermentation vessels. |
| leaves 40 to 60 percent in an active state. Curing at | | | | FERMENTATION |
| higher temperatures promotes a reaction between | | | | The simple sugars in wort are converted to alcohol |
| amino acids and sugars to form melanoidins, which | | | | and carbondioxide. Fermentation is carried out by |
| give both colour and flavour to malt. | | | | yeast, which is added, or pitched, to the wort at |
| In the first stage of kilning, a high flow of dry air at | | | | three kilograms per hectolitre, yielding, 10,000,000 |
| 500C (120F) for lager malt and 650C (1500F) for ale | | | | cells per millilitre of wort. |
| malt is maintained through a bed of green malt. This | | | | Brewing is unique among the fermentation industries |
| lowers the moisture content from 45 to 25 percent. | | | | in that yeast from one fermentation is used to pitch |
| A second stage of drying removes more firmly | | | | the next. This means that hygienic conditions and |
| bound water, the temperature rising to 700 - 750 | | | | rigorous quality control are necessary. A high |
| (1600 - 1700F) and the moisture content falling to 12 | | | | proportion of live cells and freedom from bacterial |
| percent. In the final curing stage the temperature is | | | | and other yeasts are important quality considerations. |
| raised to 750 - 900C (1700 - 1950F) for lager and 900 | | | | Traditional open-topped earthenware fermentation |
| to 1050C for ale. The finished malt is then cooled and | | | | vessels gave way to round, wooden and later |
| screened to remove root lets. | | | | square, copper-lined fermentors and brewery |
| MASHING | | | | fermentation systems evolved around the |
| Milling | | | | mechanism used to separate yeast from freshly |
| For efficient extraction with water, malt must be | | | | fermented, or green, beer. Top fermentations, in |
| milled. Early milling processes used stones driven | | | | which yeast rises to the surface, require the most |
| manually or by water or animal power, but modern | | | | elaborate systems, but most brewing operations now |
| brewing uses mechanically driven roller mills. The | | | | use more hygienically operated closed vessels and |
| design of the mill and the gap between the rolls are | | | | bottom fermentation. These vessels, erected outside |
| important in obtaining the correct reduction in size of | | | | the brewery, are several thousand hectolitres in |
| the malt. The object is to retain the husk relatively | | | | capacity (one hectolitre - 26 gallons) and are made of |
| intact while breaking up the brittle modified starch | | | | stainless steel. Temperature control is achieved |
| into particles. | | | | automatically by circulating cold liquid in jackets fitted |
| Mixing the Mash | | | | to the wall of the vessel. |
| The milled malt, called grist, is mixed with water, | | | | The temperature of the wort at pitching is 150C to |
| providing conditions in which starch, other molecules, | | | | 180C for ale and 70 to 120C for lager. As |
| and enzymes are dissolved and rapid enzyme action | | | | fermentation proceeds, the specific gravity falls as |
| takes place. The solute-rich liquid produced in mashing | | | | the sugars are converted by the yeast. The extent |
| is called the work. Traditionally, mashing may be of | | | | of fermentation is governed by the wort composition |
| one of two distinct types. The simplest process, in | | | | and by the amount of fermentable sugar to remain in |
| fusion mashing, uses a well-modified malt, two to | | | | maturing beer. During fermentation, yeast multiples |
| three volumes of water per volume of grist, a single | | | | five to eight fold and generates heat. The |
| vessel (called mashtun), and a single temperature in | | | | temperature is allowed to rise, until it reaches 200 to |
| the range of 620 to 670C (1450 to 1500F). With | | | | 230C for ale and 120 to 170C for lager. At that point |
| well-modified malt, breakdown of proteins and | | | | the fermentation is cooled to 150C for ale and 40C |
| glucans has already occurred at the malting stage, | | | | for lager, considerably slowing yeast action. Yeast is |
| and at 650C the starch readily gelatinizes and the | | | | then removed and the green beer, still containing |
| amylases become very active. Less well-modified | | | | about 500,000 yeast cells per millilitre, is transferred |
| malt, however, benefits from a period of mashing at | | | | to a conditioning or maturation vessels, where a |
| lower temperatures to permit the breakdown of | | | | secondary fermentation may take place. In traditional |
| proteins and glucans. This requires some form of | | | | brewing, the primary stage of fermentation took |
| temperature programming, which is achieved by | | | | seven days for ale and three weeks or more for |
| decoction mashing. After grist is mashed in at 350 to | | | | lagers, these times haves been shortened to two to |
| 400C (950 to 1050F), a proportion is removed, boiled | | | | four days and seven to ten days by modern |
| and added back. Mashing with two or three of these | | | | practices using more efficient fermentation vessels. |
| decoctions raises the temperature in stages to 650C. | | | | MATURATION AND PACKAGING |
| The decoction process, traditional in lager brewing, | | | | Priming and Krausening |
| uses four to six volumes of water per volume of | | | | A slow secondary fermentation of residual or added |
| grist and requires a second vessel called the mash | | | | sugar (called primings), or in lager brewing, the |
| cooker. | | | | addition of actively fermenting wort (called Krausen) |
| Other sources of starch that gelatinize at 550 to | | | | generates carbondioxide, which is rented and purges |
| 650C can be mashed along with malt. Wheat flour | | | | the green beer of undesirable volatile compounds. |
| and corn (maize) flakes may be added directly to the | | | | Continued yeast activity also removes strong |
| mash, whereas corn grits and rice grits must first be | | | | flavouring compounds such as diacetyl. Allowing |
| boiled in order to gelatinize. Their use requires a third | | | | pressure to build up in the sealed vessel then |
| vessel, the cereal cooker. | | | | increases the level of carbonation, giving the beer its |
| Modern mashing system use mixed grists and mash | | | | "condition". In traditional brewing, large volumes of ale |
| mixers, which are efficiently stirred and | | | | were conditioned. In tanks for seven days at 150C, |
| temperature-programmed mashing vessels. Enzymes | | | | whereas lagers were matured at 00C (320F) for up |
| of bacterial and fungal origin may be added as aids. | | | | to three months. These long maturation periods were |
| Ale and lagers are mashed in the same equipment, | | | | caused by the precipitation of protein tannin |
| but they require different temperature programs and | | | | complexes, which at low temperatures form "chill |
| grist composition. Modern breweries often practice | | | | hazes" that are slow in setting out. Modern practice |
| high-gravity brewing, in which highly concentrated | | | | speeds up this process by adding excess tannin, |
| worts are made, fermented, and then diluted, | | | | clarifying with protein or tanning adsorbent, or using |
| allowing more beer to be brewed on the same | | | | enzymes to degrade the proteins. |
| equipment. | | | | Packaging |
| Separating the Wort | | | | Traditional, or "real", ales are packaged into casks. |
| The mashtun used in infusion mashing is fitted with a | | | | Sugar primings, clarifying agents such as isinglass |
| false base containing precisely machined slots through | | | | finings and whole hops are added and the beer is |
| which the husk, preserved during milling, cannot pass | | | | transferred to the point of sale, where it is carefully |
| the trapped husk thus forms a filterbed that | | | | rented to the proper level of conditioning before |
| removes solids from the wort as it is drained, leaving | | | | being sold. |
| a residue of spent grains. Wort separation takes four | | | | Beer produced on a large scale in modern breweries |
| to sixteen hours. For through extraction, the solids | | | | is kept free of oxygen, filtered through cellulose or |
| are sprayed, or sparged, with water at 700C. | | | | diatomaceous earth to remove all yeast, and |
| The decoction brewer transfers the mash into | | | | packaged at 00C under pressure of carbondioxide. |
| separation vessel called the lautertun, where a | | | | Beer produced by high-gravity brewing is diluted to |
| shallow fitter bed is formed, allowing a more rapid | | | | the desired alcohol concentration, immediately prior to |
| runoff time of about 2 ½ hours. Large modern | | | | packaging, with oxygen-free carbonated water. Most |
| breweries use either lautertuns or special mash filters | | | | beers packaged in bottles or metal cans are |
| to speed up the runoff and conduct 10 or 12 mashes | | | | pasteurized in pack by heating to 600C for five to 20 |
| a day. As much as 97percent of the soluble material | | | | minutes. Beer is also packaged into metal cans are |
| is obtained, and 75 percent of this is fermentable. | | | | pasteurized in pack by heating into metal kegs of 50 |
| Wort is approximately 10 percent sugar, and it | | | | litre capacity after pasteurization at 700C for five to |
| contains amino acids, salts, vitamins, carbohydrate | | | | 20 seconds. Modern packaging machinery is designed |
| and small amounts of protein. | | | | to operate hygienically, exclude air and run at rates |
| BOILING | | | | of 2,000 cans or bottles per minute. |