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(詳細はbrewing of coffee requires using the quantity of coffee, ground precisely, extracted to the correct degree, controlled by the correct time and correct temperature. == Concepts == More technically, coffee brewing consists of dissolving soluble flavors from the coffee grounds in water. Specialized vocabulary and guidelines exist to discuss this, primarily various ''ratios,'' which are used to optimally brew coffee. The key concepts are: ;Extraction: Also known as "solubles yield" or "Extraction Yield" – what percentage (by weight) of the grounds are dissolved in the water. Put simply, how much of the coffee in the brewer ends up in the cup. ;Extraction yield %: The percentage by mass of coffee grounds that ends up dissolved in the brewed coffee. Extraction yield % = Brewed Coffee() x TDS() /Coffee Grounds() E.g. (espresso) 36g brewed coffee x 10% TDS / 18g ground coffee = Extraction yield of 20% ;Total Dissolved Solids (TDS): If you have a standard refractometer the TDS is expressed in parts per million. (ppm). To convert ppm into a percentage: Divide the ppm by 10000. E.g. 10000ppm /10000 = 1% ;Strength: Also known as "solubles concentration", as measured by Total Dissolved Solids – how concentrated or watery the coffee is. ;Brew ratio: The ratio of coffee grounds (mass) to water (volume): how much coffee is used for a given quantity of water. This may be expressed in units of either grams per litre or ounces per US half gallon. These are related as follows: :Strength = Brew ratio × Extraction which can be analyzed as the following identity: :dissolved solids/water = grounds/water × dissolved solids/grounds A subtler issue is ''which'' solubles are dissolved – this depends on solubility of different substances at different temperatures, changes over the course of extraction (different substances are extracted during the first 1% of extraction than in the period from 19% extraction to 20% extraction), and is primarily affected by ''temperature.'' Brewing guidelines are summarized in ''Brewing Control Charts,'' which graph these elements, and center around an "ideal" rectangle indicating the target brewing range. The yield is the horizontal (''x''-axis), the strength is the vertical (''y''-axis), and a given brewing ratio determines a radial line, since for a given brewing ratio the strength is directly proportional to the yield. In brief, ideal yield is widely agreed to be 20%±2% (18%–22%), while ideal strength (for brewed coffee) varies between 1.25%±.10% (1.15%–1.35%) in American standards, to 1.40%±.10% (1.30%–1.50%) in Norwegian standards, with European standards falling in the middle at 1.20%–1.45%). This is most easily achieved with a brewing ratio of 55 g/L (55 grams of coffee per 1 L of water) in American standards, to 63 g/L in Norwegian standards, yielding approximately 14–16 grams of coffee for a standard 240 ml (8 oz) cup. These guidelines apply regardless of brewing method, with the following exceptions: espresso is significantly different (much stronger, and more varied extraction), and dark roasts taste subjectively stronger than medium roasts (standards are based on medium roasts; equivalent strength requires using a lower brewing ratio for darker roasts). These components are addressed in turn. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Coffee extraction」の詳細全文を読む スポンサード リンク
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