And here is the last part of the history and properties of coffee. What is the best method to infuse it? How can we serve it and maintain its temperature? Keep reading and discover more curiosities.
And here is the last part of the history and properties of coffee. What is the best method for brewing it? How can we serve it and maintain its temperature? Keep reading to discover more curiosities.
- Brewing Methods.
There are several different methods for brewing coffee. Almost all of them extract between 20 and 25% of the substance from the bean, producing a cup that contains between 1.3 and 5.5% solids.
Typical American coffee, made with a drip coffee maker, is the weakest, while Italian espresso is the strongest. The coffee-to-water ratio is 1:15 for American coffee and 1:5 for espresso. A clear conclusion from the previous table is that it’s always better to use more coffee than less. A strong but balanced cup can be diluted with hot water and will remain balanced, but weak coffee cannot be improved. This principle can help avoid problems caused by variations in cup and spoon sizes, as measurements are very approximate.
Each brewing method has its drawbacks. Percolators work at boiling temperatures and tend to over-extract. Many automatic drip coffee makers cannot deliver water near the boiling point and, to compensate, brew for a long time, resulting in loss of aroma and some bitterness. Manual drip filters allow little control over the extraction time. French press coffee makers leave small particles suspended in the brew, which continue to release bitterness. The Italian Moka coffee maker, placed on the stovetop, operates above the boiling point, at around 110°C, producing a somewhat rough beverage. Cold-brewing coffee overnight in cold water does not extract as many aromatic compounds from the ground coffee as hot-water methods.
- Espresso Coffee.
True espresso coffee is made very quickly, in about 30 seconds. A plunger, a spring, or an electric pump pushes water at 93°C through finely ground coffee at 9 atmospheres of pressure.
The amount of ground coffee is three to four times greater than that used in non-pressurized brewing, and the concentration of coffee materials in the brew is also three to four times higher, resulting in a substantial and velvety body and intense flavor.
Among the extracted materials, there is a relatively large amount of coffee oils, which the high pressure forces out of the coffee particles, forming a creamy emulsion of tiny droplets that contribute to the slow and prolonged release of flavor in the mouth, long after the last sip.
Another unique feature of espresso is the crema, the creamy and quite stable foam that forms on the surface of the brew. It is a consequence of gaseous carbon dioxide trapped in the ground coffee and the mixture of dissolved and suspended substances: carbohydrates, proteins, phenolic materials, and large aggregates of pigments, all of which interact with each other in various ways and maintain the walls of the bubbles.
- Serving and Maintaining Coffee.
Freshly brewed coffee is best enjoyed immediately because its flavor is fleeting. The ideal temperature to drink it is around 60°C, when a sip doesn’t scald the mouth, and all the coffee’s aroma is released. As it cools in the cup, coffee is usually left in the coffee maker just below the infusion temperature.
Strong heat accelerates chemical reactions and the escape of volatile molecules, so the taste of coffee changes noticeably in less than an hour. The best way to keep coffee hot is to preserve the original heat in a preheated, insulated, and closed container, not on a hot plate that constantly supplies excessive heat from below while allowing heat and aroma to escape from above.
- The Taste of Coffee.
Coffee has one of the most complex flavors among all our foods. The base is an exquisite balance of acidity, bitterness, and astringency. One-third or less of the bitterness is due to caffeine, which is easily extracted; the rest is due to phenolic compounds and slower-extracting brown pigments. More than 800 aroma components have been identified, contributing notes described as nuts, earth, flowers, fruit, butter, chocolate, cinnamon, tea, honey, caramel, bread, toasted, spices, and even wine and game meat.
Robusta coffees, which contain more phenolic substances than Arabica, develop a characteristic aroma of smoke and tar, valued in dark roasts. Milk and cream reduce coffee’s astringency because they provide proteins that bind to phenolic and tannic compounds, but these liquids also block aromatic molecules and weaken the overall coffee flavor.
- Decaffeinated Coffee.
Decaffeinated coffee was invented in Germany around 1908. It is made by soaking green coffee beans in water to dissolve the caffeine, extracting the caffeine from the coffee beans with a solvent, and treating the beans with steam to evaporate any remaining solvent. In the “Swiss” or “water” process, water is the only solvent used, and caffeine is extracted from the water with charcoal filters, with other water-soluble substances added back to the beans. Some organic solvents used in other processes were suspected to be hazardous to health even in the tiny amounts that remain in the beans. The most common one, methylene chloride, is now considered safe. More recently, high-pressure carbon dioxide has been used, which is non-toxic.
While a regular coffee infusion may contain 60-180 mg of caffeine per cup, decaffeinated coffee contains only 2 to 5 mg.
- Instant Coffee.
Instant coffee became commercially viable in Switzerland just before World War II.
It is made by brewing ground coffee near the boiling point to extract aroma, and then a second time at 170°C and high pressure to maximize the extraction of pigments and carbohydrates that provide body. The water is removed from the extracts by drying with hot air or freezing, preserving most of the volatile compounds and achieving a fuller flavor. The two extracts are then mixed and supplemented with flavors captured during the extraction phase.
Instant coffee crystals contain approximately 5% moisture, 20% brown pigments, 10% minerals, 7% complex carbohydrates, 8% sugars, 6% acids, and 4% caffeine. Being essentially dry concentrate, instant coffee is very useful for flavoring baked dishes, jams, and ice creams.