November, 2000: The Netherlands
When ordering beer in the Netherlands, you must do as the Dutch do: If the draft does not arrive with two fingers of froth on top, send it back. Beer, an alcoholic beverage made from grain, hops, yeast, and water, is serious business in the Netherlands. Any native will tell you that beer is as Dutch as windmills and tulips. The Heineken brewery, an 1864 vision of Gerard Adriaan Heineken, produces over 7.4 billion liters annually, second only to the American brewery Anheuser Busch. Besides the Heineken label, the company produces Murphy's Stout, Irish Red, Irish Amber, Grolsch, and Amstel.
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Steps in the beer-making process.
The exact origins of beer are not known, but it is believed to have been made for more than 10,000 years, though the specific grain used has varied geographically. For example, wheat (Triticum spp.) was used in Mesopotamia, rice (Oryza sativa) in Asia, and sorghum (Sorghum spp.) in Africa. All three are members of Poaceae, the grasses.
The two main species of yeast (Kingdom Fungi) used to produce beer are Saccharomyces cerevisiae and S. uvarum. The grain, usually barley, is soaked in water to induce germination. During the germination process, the enzyme diastase is produced, catalyzing the hydrolysis of starch to maltose, C12H22O11. (Maltose is a disaccharide, and starch is a polysaccharide.)
diastase
C6H10O5)n + H2O -----> C12H22O11
where n=2 in order to balance this particular equation, yielding one unit of maltose.
This maltose mixture is referred to as malt and is prevented from germinating further by the addition of heat. The dried malt is then milled, rupturing the pericarp to facilitate the outflow of sugars when soaked in water. After several hours of soaking, the sweet water, called wort, is boiled to destroy any bacteria (Kingdom Monera) that may be present. Hops are added to the boiling wort, giving it either a subtle or an intense, bitter flavor, depending on the type and amount of hops used and the length of the boiling time. The wort is cooled, strained, and transferred to a fermentation vat. The yeast is added and, depending on the species of Saccharomyces involved, optimum temperatures are maintained to eventually transform the wort to beer. The beer is then aged in airtight tanks where fermentation continues. (Some breweries add additional CO2 at this point in the process.) Fermentation is a form of anaerobic respiration; specifically, it is alcoholic fermentation that produces ethyl alcohol, C2H5OH and CO2, in addition to ATP (energy currency). The reaction looks like this:
enzymes
C6H12O6 -----------> 2 C2H5OH + 2 CO2 + ATP
Again, depending on the type of beer, the liquid is aged anywhere from weeks to months and then filtered to produce the familiar translucent liquid. After the final process of pasteurization to kill any remaining yeast, the beer is ready for sale and consumption.
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The barley plant.
Barley, Hordeum spp., is in the Poaceae family. Although some species of Hordeum are cultivated ornamentals and others are weedy herbs, most are grown for human consumption, as in the brewing process. The flowers form in dense spikes, and barley has parallel venation, as is typical of this family of monocots.
Hops, members of the Cannabaceae family, are dioecious plants. While the male flowers are arranged in loose panicles, the female flowers are produced in aromatic catkins that are harvested in late summer for use in brewing. The female catkin is covered with lupulin, a yellow powder commonly referred to as hop flour. Chemical analysis of lupulin reveals bitter substances, including the alkaloids codeine and morphine, which are responsible for the bitter flavor of hops. Lupulin is sometimes collected and used as a sedative. Historically, the Swedes used Humulus fibers to make paper and cloth, and the Romans ate the shoots as a vegetable just as we eat asparagus. The common hop, Humulus lupulus, and the American hop, Humulus lupulus variety lupuloides, are extensively cultivated for use in brewing.
In Amsterdam, visitors can tour the Heineken Museum, located on the Weteringschans in the center of the city. The trip through the museum traces both the beer-making process and the history of Heineken from its humble beginnings to its present dominance. All tours culminate in the wooden beer hall for a drink of the golden liquid–just make sure it has two fingers of froth on top.
References, Websites, and Further Reading
http://www.beetrown.org/ Home of the Association of Brewers
http://www.allaboutbeer.com/aabmhome.html All About Beer magazine
http://www.heineken.com Heineken homepage
http://encarta.msn.com "Hop," Microsoft® Encarta® Online Encyclopedia 2000. © 1997—2000 Microsoft Corporation.
http://encarta.msn.com "Beer," Microsoft® Encarta® Online Encyclopedia 2000. © 1997—2000 Microsoft Corporation.
Stern, Introductory Plant Biology, 8th Edition
Chapter 2: The Nature of Life
Hydrolysis, p. 22
Carbohydrates, pp. 22—23
Enzymes, p. 26
Chapter 8: Flowers, Fruits, and Seeds
Structure of flowers, pp. 129—32
Germination, pp. 143—45
Inflorescence types, fig. 8.7
Monocot grain structure, fig. 8.29A
Chapter 10: Plant Metabolism
Respiration (and anaerobic fermentation), pp. 178—83
Chapter 17: Kingdom Monera and Viruses
Bacteria, pp. 280—96
Chapter 19: Kingdom Fungi and Lichens
Yeast, pp. 334—57
Chapter 24: Flowering Plants and Civilization
Monocots and Poaceae, p. 454
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