- The Washington Times - Thursday, March 20, 2003

What makes a good cup of coffee? Anyone can say what he or she likes best about America's favorite drink, but few people can explain the science behind their preferred brew.
Coffee, above all, is about personal preference the choice of roast, grind and brewing method. Ultimately, however, taste begins with the bean, which, technically, is a seed.
Two seeds rest within each fruit (called a cherry) of the coffee plant. As with most agricultural products, the size and development of the beans depend on the quality of the soil and the environment in which the plants are grown.
The two main species grown today are Arabica, the most popular by far, and Robusta, which is hardier and contains more caffeine but produces an inferior-tasting beverage. The countless selections offered by coffee shops refer to different roasting styles or to countries of origin, not to their botanical origins like Arabica or Robusta.
Coffee plants thrive in tropical climes at elevations between 3,600 and 8,000 feet. The main coffee-producing countries are Brazil, Vietnam and Colombia.
Generally speaking, the higher the elevation, the more complexity and acidity results, says Cecile Hudon, a senior education specialist for Starbucks, the Seattle-based corporation that has 150 stores in the Greater Washington area.
Another key factor is the method chosen to remove the bean from the cherry, which is done by either a wet or a dry process. The dry process involves leaving the cherries out to dry before the seeds are removed. The wet method uses water to separate them.
"Dry processing produces a more complex cup," says California-based author and teacher Kenneth Davids, who has been studying coffee for three decades. Complexity, he notes, is "a way of describing a flavor that shifts among pleasurable possibilities and does not completely reveal itself at any one moment." He defines flavor as a synthesis for categories of acidity, aroma and body.
The earliest coffees, such as those from Yemen, were produced by the dry method, he says. "The wet method is classically employed in Central America and East Africa two prime coffee-producing areas. The wet method is better only because the coffee is not dried inside the fruit, which, left out too long, can attract molds and sugars that can ferment. But the wet method can destroy some of the complexity."
These are just some of the considerations that led Mr. Davids to claim that coffee requires a much more educated devotee than wine does to understand how best to make and enjoy it.
"It's not an assertion, but a statement of fact," he contends, "because the consumer needs to brew the coffee. You don't brew wine. Furthermore, coffee is roasted in a different location from which it is grown, whereas in high-quality wine, everything is done at the source. Coffee requires two procedures, and to produce a good cup, you need more sophisticated and active participation."
Then, too, he says, coffee "is more chemically complex, containing a minimum 400 chemical compounds affecting our sensory perception. There could be more, depending on how you judge it."
The chemistry in that beautiful brown brew with the unmistakable and tantalizing aroma is different at different times, he adds at five seconds after the brewing process is complete and at five minutes.
Most consumers rely on wholesalers to roast their coffee before purchase. Before roasting, the green beans are full of nutritional content primarily vitamin C, Mrs. Hudon says. For this reason, the pulp and husk of the fruit often get used as fertilizer, according to the Web site www.coffeeresearch.org.
"Given a good-quality bean, roasting is probably the single most important factor influencing the flavor of coffee," Mr. Davids wrote in the fifth edition of his popular book "Coffee: A Guide to Buying, Brewing and Enjoying." A darker bean the result of being kept longer in the roaster at a higher-than-average temperature produces a tangy and bittersweet flavor, which is considered ideal, he says. This is a delicate operation because if left too long, the bean turns into charcoal.
The composition of a green bean is similar to that of other nuts and kernels in its mix of mostly fats, proteins and fiber. The coffee's distinctive aroma and flavor are a result of roasting the bean. The heat in the roaster takes out much of the bean's moisture and, at the same time, brings out a volatile oily substance in the mix of solids. Without this oily substance just half of 1 percent of the bean's weight drinkers wouldn't have coffee as they know it but, in Mr. Davids' words, "only sour brown water and caffeine."
Starbucks roasts all the beans sold and used in both its East Coast and European outlets at a facility in York, Pa.
The M.E. Swing Co., a family-owned operation since 1916 that sells coffee at both retail and wholesale outlets, roasts nearly all its coffee and beans at a facility in Alexandria. (The company imports Hawaiian Kona and Jamaican Blue Mountain already roasted because demand for them is small.)
"The final test is in the cup," says Swing's manager, Dwayne Walker. Whether done commercially or in the home and whether done by machine or by hand, the brewing process involves what Starbucks' "coffee educators" call four primary fundamentals: proportion, grind, water and freshness.
Proportion is the amount of ground coffee measured against the amount of water. Two tablespoons of ground coffee are recommended for every six ounces of water for the best extraction rate as determined by the Coffee Growers Association.
A different size grind is needed for different brewing methods. The two main types of grinding machines are the blade style and the burr or mill grinder style. A blade is less effective because there is less control and hence less consistency. "The blade just cuts it up, whacking away," Mr. Walker says. Thus, the grind is less uniform.
Starbucks believes that the coffee press, also known as French press or plunger method, is best for brewing. Mr. Davids and Mr. Walker favor filter and vacuum methods.
The press method, Mr. Davids says, produces a cup heavy with colloids that he describes as "heavy globs to give a sense of body to coffee. And [with the press] there tends to be a suspended silt in the coffee. If you like a kind of heavy cup with a slightly sharp, gritty taste, then you would use French press. With French press, there is a metal screen, whereas most drip coffee is done with a paper filter."
The size especially the thickness of the filter can be a determining factor as well. A thick filter, such as the Chemex paper version or the one found in metal mesh devices, requires a slightly coarser grind. "If you use a mesh filter, you get coffee with a lot of colloids because more silt goes through it," he says. "For me, the best is to pour water over coffee in the filter and stir it with a long-handled soda spoon as you pour it in to assure a more complete extraction."
Specialists all agree that too fine a grind traps water and prevents full flavor from emerging, while too coarse a grind produces a poor extraction of flavor and results in weak coffee. A Melitta filter method requires a finer grind; the plunger method takes a coarse grind. The plunger device gives the coffee a longer time to interact with the water. A fine grind used in filter methods is surrounded by water for a shorter time.
The kind of water and the temperature at which water is heated also affect the taste. Filtered water free of impurities or clean fresh water is ideal. Coffee should be stored away from too much light in airtight glass containers and ground fresh each time it is made.
Authorities advise against storing beans in the freezer or refrigerator, where they are liable to be affected by moisture from condensation, which can dilute the flavor inherent in the bean. The very best storage area would be anywhere away from extreme heat and light. "Coffee draws moisture and odors from its surroundings," Mr. Walker says. "If possible, beans should be used within two weeks of purchase; after that time, they start to lose their body."
Another basic rule is not to boil coffee or leave the brew on a burner. Too low a temperature results in an underextraction of the flavors; too much interferes with taste and can make the coffee bitter.
The ideal is to make coffee "just off the boil." Water boils at 212 degrees, so it's best to pour the water onto grounds when it is between 198 degrees and 205 degrees. (A high-quality automatic coffee maker controls the heat better than a standard glass Melitta or Chemex filter device, Mr. Walker says.) Microwaving coffee isn't a good idea because it is simply another method of heating.
The standard percolator is not recommended for brewing, either, because the coffee is constantly being boiled and brought to the top container holding the grounds, resulting in the loss of some of the volatile flavors.
"After three minutes on a warmer, [coffee] will start to break down. After half an hour, it will usually be undrinkable," warns the Coffee Masters Web site (www.coffeemasters.com). "If you need to keep brewed coffee warm for a long period, use an insulated vessel like a thermal carafe or vacuum flask, which will keep the coffee warm without heating."
Decaffeinated coffee begins life as a green bean; the caffeine is extracted either through what is known as a Swiss water method, which takes out the caffeine elements by percolation through activated charcoal, or through a direct-contact method, which uses chemical solvents selective to the caffeine. A third, less common separation method uses carbon dioxide.
Mr. Davids maintains that the taste of the best decaffeinated coffee, when freshly roasted and ground and carefully brewed, can stand comparison with untreated coffee, but he concedes that because decaffeinated beans are hard to roast, fine decaf is not the norm.
Powdered instant coffee is made by brewing coffee in large containers and then evaporating the water from the brew, resulting in powder crystals. Freeze-dried instant is made by freezing fresh-brewed coffee and putting it under pressure. Moisture in the form of ice is drawn out, leaving dry coffee crystals.
Mr. Davids' explanation of coffee's global popularity: "Coffee is a very aromatic and stimulating package that becomes a sort of positive thing in the memory."

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