The Effects of Water on the Taste of Coffee

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Since 99 percent of a cup of coffee is water, the effect of water quality on coffee quality can hardly be ignored. If you don’t like the taste of the water that comes out of your tap, it makes no sense to think making coffee with that water will produce a palatable beverage. Merely because water is safe to drink is no indication that it is pleasant to drink. Chlorination, excessive hardness, alkalinity, brackishness, organic content, and other factors affecting water quality found in local water supplies can downgrade brewed-coffee quality. Sivetz states that at least half the coffee brewed in water available, and in some areas a good brew quality is impossible to achieve. The best water for coffee is free of off-tastes, odors, and impurities, not overly soft or alkaline, and possession a mild mineral content, or slightly hard. On this basis the Northeast, the Pacific Northwest, and parts of the South have the best general water conditions, though of course local conditions—or even the individual conditions found in your basement water pipes-- are just as important. Artificially softened water, for example, makes poor coffee.
What can you do if your local water supply is poor? Considering that most coffee drinkers do not drink a great many cups per day, using filtered or bottled water may provide the answer without a great deal of additional expense. Steam distilled water, in addition to being de-arated (and there fore somewhat flat-tasting), yields somewhat sourish coffee, perhaps because of excessive extraction. Some bottled 'spring” waters have too much mineral content and fail to extract enough flavor from the grounds. You may have to experiment with coffee made from various bolted waters or filtered tap water to find an appropriate substitute for poor local water. If excessive chlorination is the problem, simply letting water stand in a large pot for a few hours to a day may bring about a marked improvement in the water, and thus your coffee.
Even in areas with high-quality water, be sure to use only cold, freshly drawn water. Letting the tap run for a few moments before filing the kettle ensures that the stale, flat, de-aerated water that has been left standing in the pipes has run off. Do not use water from the hot-water tap; this is certainly quite stale and flat from siting in the boiler.
One of the principal causes of poor coffee made in most United States homes (and restaurant, too) is that too much water is used in proportion to the amount of ground coffee used. In spite of efforts by industry trade organizations, some coffee firms still make excessive claims for how many cups of coffee can be made from a pound of their blend. At one time in the United States it was common claim that up to seventy-five cups could be made from one pound of coffee, even though it is hardly in the industry’s interest to claim that more servings can be made from less coffee. No one has ever been able to show how more than about forty—fifty at most—servings can be made from a pound of beans with out a diminution in beverage quality. What is more, this “serving” or “cup” is a six -ounce cup, not an eight- or ten-once mug.
The ideal proportion of coffee is one standard coffee measure (two level tablespoons of ground coffee) per six ounces of water. This relationship holds true regardless of the method used. The only exceptions to this rule are double-strength coffees. These include French café filtre, and other coffees made in a Moka-type pot or an Italian machinetta. (Since these double-strength coffees are traditionally served in small demitasse cups, for convenience we'll refer to them as demitassse coffees.) These coffees require two standard coffee measures (or four level tablespoons) per six-ounce serving. Other coffees requiring a higher-than-normal proportion of coffee to water are espresso and Turkish coffee.
The proportion of two level tablespoons per six-ounce serving is considered ideal because it yields a brew with excellent strength: not weak, but not too strong. The strength of a cup of coffee can actually be measured by the concentration of solubles found in the beverage (this is easy enough to determine with hydrometer, which tells you how many solids are dissolved in the liquid), and this strength is directly related to the proportion of coffee used in a given amount of water. Using a recommended measure of coffee to water, one gets forty servings per pound, of which each serving has from 1.15- to 1.35-percent soluble solids. Trying to get more servings form a pound --making the coffee weaker—will result in less than 1.15-percent soluble solids in the beverage and a brew that will be excessively strong for most tastes. The exceptions here again are the demitasse coffees, whose extra strength is tolerable because they are served in small amounts.
Excessive extraction (causing bitterness) is not the same as excessive strength; it is possible to make a weak (low-strength) but bitter cup by grinding coffee excessively fine, using less than the recommended proportion, and boiling it for ten minutes on the stove. The result will be thin, watery,and bitter. It is also possible to make an excessively strong, but underdeveloped (flavorless) cup by using a very coarse grind in twice the recommended amount through a filter cone. The coffee will be strong, but lack coffee character. Probably one of the reasons Americans often make coffee to weak is that the methods they use often result in over extraction. To avoid the resulting bitterness, many use less coffee. Many people think they don't like full-strength coffee,when in fact they have simply never had a properly brewed cup made in the proper proportion. In order to brew coffee properly, it should be made full-strength, and then, some claim, if it is still to strong,it can be deluded with hot water in the cup. While this is certainly preferable to brewing it weak, we find that dilution degrades the coffee's character. Before resorting to dilution, try simply switching to a milder coffee—a lightly roasted Brazilian Santos, for example.
In short, proper measuring of the coffee and the water is a must. Many coffee pots and coffee makers do not have accurate cup markings, so check these first before relying on them. Although few people will be willing to go to such lengths, it is true that coffee is more accurately measured by weighing than by cubic measure, because coffees “bulk” differently according to roasts and origin. For those who are interested in pursuing the ultimate in coffee perfection, the weight equivalent of the recommended proportion is ten to eleven grams per six ounces of water. For those making large amounts of coffee, this is 1 pound of coffee to 2 1/2 gallons of water. Some useful measurements in between are: for 3 cups of coffee use 1 ounce of coffee to 16-20 ounces of water; for 8 cups (48 ounces) of coffee use 2.4-3 ounces;for 10 cups (60 ounces) use 3-3.75 ounces of coffee. Our personal preference is for coffee made all the upper-strength limits.
The temperature of the water used is another important factor in proper coffee-brewing. The ideal temperature for water when it comes into contact with the ground coffee is 200°F: in fact, the temperature of the water should vary no more than plus or minus 5° from this norm. Fortunately, achieving this sort of precision does not require anything fancy in equipment, since it is the range of temperature that a pot of boiling water falls to the moment it is removed from the heat. In a number of coffee-making methods—drop, filter cone, vacuum, and so on—water must first be brought to a boil and then added to the ground coffee, often by simply poring the water on the grounds. Water brought to a boil in a kettle will fall to the required temperature as the kettle is lifted from the heat and the water is poured. Bring the water to full boil, but do not let it boil any length of time, as this will drive off the air in the water and deaden the taste.
In order not to impart any foreign flavor to the water, we recommend using a stainless-steel kettle, rather than any old saucepan, although a porcelain pot would seem unproblematic, Many people use whistling kettles, but these have one considerable drawback: the narrow neck makes it impossible to clean the kettle. If you've ever had occasion to look inside a kettle used for a year or two you're liable to be startled by the extraordinary build up of mineral and other deposits left as accumulated residue from the boiling of hundreds of gallons of tap water. Needless to say, these formations don’t help the character of the freshly drawn water, since it is being boiled in their presence—not to mention that most of this material does not look like the sort of thing most people would care to imbibe purposely along with their coffee. We happen to use the stainless-steel bottom with half of a vacuum coffee pot; with the lid on, it boils as fast as the usual kettle and can easily be cleaned, since its wide mouth will admit an entire hand. Any similar-design kettle would doubtless work as well. We have been told that it may be something of a possible health hazard to scour the inside of such a kettle with an abrasive pad, since scouring the surface may allow small amounts of chromium to be leached into the water, depending on the alloy of the metal. Aside for two every once in a while with the sort of plastic scrubbing pad that is recommended for use with Teflon products is all that we've found necessary to clean our kettle, at least if it’s not used for anything else. We find no inconvenience in not having a whistle, since we almost always first put the water on to boil, and then select and grind the coffee, prepare the pot, ready cups and like, after which time the water is often at a boil.

pp. 107-111 of Coffee and Tea by Ellin McCoy & John Frederick Walker (1991)

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