Expresso is made by forcing water through the grounds with high pressure. Through this process, a higher percentage of the beans oil is extracted, which emulsifies into the brew and gives the drink a velvety texture. The concentration of coffee is three or four times greater in expresso than on unpressurized brews. Expresso also forms a characteristic foam, called the crema, which is the product of carbon dioxide gas and the mixture of dissolved and suspended carbohydrates, proteins, phenolic materials, and pigment aggregates.
Decaffeinated coffee was invented in Germany in 1908. It is made by soaking the green coffee beans in water to dissolve the caffeine, then extracting the caffeine with a solvent, and steaming the beans to evaporate any remaining caffeine. Ordinary coffee contains 60-180 mg of caffeine per cup. Decaff contains 2-5 mg.
Instant coffee is essentially a dry concentrate. It is made by boiling ground coffee in duplicate to obtain maximum extraction of pigments and carbohydrates. Later it is dehydrated and supplemented with aromas. It is used in baking, confections, and ice cream.
Showing posts with label coffee. Show all posts
Showing posts with label coffee. Show all posts
Thursday, March 29, 2012
Tuesday, March 20, 2012
Brewing and drinking coffee
There are many different methods for brewing coffee. Most methods extract between 20 - 25% of the coffee substance. Standard American filter-drip coffee is the lightest, making a proportion of 1:15 coffee to water. Italian expresso is the strongest at a 1:5 ratio. Brewing coffee is an art, as the results depend on type of drip, temperature, and length of time.
Coffee tastes the best when freshly brewed and consumed. The ideal temperature for sipping is 140 degrees F. It loses aroma and flavor in less than an hour in the pot. It is best to keep hot coffee within its original heat in a preheated, insulated, closed container than on a hot plate, as excessive heat speeds the escape of aroma and flavor.
Coffee tastes the best when freshly brewed and consumed. The ideal temperature for sipping is 140 degrees F. It loses aroma and flavor in less than an hour in the pot. It is best to keep hot coffee within its original heat in a preheated, insulated, closed container than on a hot plate, as excessive heat speeds the escape of aroma and flavor.
Making coffee
Coffee beans are prepared in the following manner:
First, the ripe berries of the coffee tree are picked and the seeds cleaned by one of two methods. In the dry method, berries are exposed to the sun to dry and ferment, then the fruit is mechanically removed. In the wet method, most of the pulp is rubbed off by machine, and the remainder is liquified by fermenting microbes. Then, the seeds are washed and dried to 10% moisture. The parchment shell is removed, sugars and minerals are leached out, and finally the beans are roasted.
Raw green coffee beans are hard. Roasting transforms them into fragile pockets of flavor. Coffee beans are roasted for 15 minutes or less at temperatures between 375 to 425 degrees F. As the temperature approaches the boiling point of water, the moisture inside the beans turns into steam and puff up the bean (similar to popped corn). At the higher temperatures, proteins, sugars, and phenolic materials break and react with each other in typical Maillard (browning) reactions. The roasted aroma, dark pigment, and flavor develop. At 320 degrees F, the Maillard reactions become self sustaining. The molecular breakdown gnerates more water vapor and carbon dioxide gas. If roasting continues, oil escapes the damaged cells and provides a visible gloss to the surface of the beans. Medium roasts give the fullest brews. The darker beans tend to be more bitter from resulting browning reactions. Once the desired roasting is achieved, the beans are cooled off rapidly.
Coffee keeps reasonably well for a couple of weeks at room temperature and a couple of months in the freezer. Once the beans are ground, the shelf life is only a few days at room temperature.
The key to grinding coffee is to obtain a standard particle size. Too large of a particle makes it hard to control the extraction. Too small particles have a larger surface area that comes in contact with the water, which often leads to overextraction and a bitter flavor. Grinders that allow small pieces to escape before getting too small give more consistent particle sizes and better brews.
First, the ripe berries of the coffee tree are picked and the seeds cleaned by one of two methods. In the dry method, berries are exposed to the sun to dry and ferment, then the fruit is mechanically removed. In the wet method, most of the pulp is rubbed off by machine, and the remainder is liquified by fermenting microbes. Then, the seeds are washed and dried to 10% moisture. The parchment shell is removed, sugars and minerals are leached out, and finally the beans are roasted.
Raw green coffee beans are hard. Roasting transforms them into fragile pockets of flavor. Coffee beans are roasted for 15 minutes or less at temperatures between 375 to 425 degrees F. As the temperature approaches the boiling point of water, the moisture inside the beans turns into steam and puff up the bean (similar to popped corn). At the higher temperatures, proteins, sugars, and phenolic materials break and react with each other in typical Maillard (browning) reactions. The roasted aroma, dark pigment, and flavor develop. At 320 degrees F, the Maillard reactions become self sustaining. The molecular breakdown gnerates more water vapor and carbon dioxide gas. If roasting continues, oil escapes the damaged cells and provides a visible gloss to the surface of the beans. Medium roasts give the fullest brews. The darker beans tend to be more bitter from resulting browning reactions. Once the desired roasting is achieved, the beans are cooled off rapidly.
Coffee keeps reasonably well for a couple of weeks at room temperature and a couple of months in the freezer. Once the beans are ground, the shelf life is only a few days at room temperature.
The key to grinding coffee is to obtain a standard particle size. Too large of a particle makes it hard to control the extraction. Too small particles have a larger surface area that comes in contact with the water, which often leads to overextraction and a bitter flavor. Grinders that allow small pieces to escape before getting too small give more consistent particle sizes and better brews.
Monday, March 19, 2012
Coffee
Coffee trees are native to Africa. They produce a red berry that contains two large seeds or "beans." The history of roasted coffee dates back to the 14th century Arab nations. From then, the coffee tree was taken to India in the 1600s, after which it was taken to Java and then to the French Caribbean. Today Brazil, Vietnam, and Colombia are the largest exporters of coffee.
There are two main trees that produce coffee beans: Coffea arabica, native to the Sudan, produces "arabica" beans; and Coffea canephora, native to West Africa, produces "robusta" beans. About 2/3 of the beans in the international trade are arabica beans. They develop a more complex and balanced flavor than robustas. They also contain less caffeine, less phenolic material, and more oil and sugar. Robustas are only popular because the trees themselves are more disease resistant.
There are two main trees that produce coffee beans: Coffea arabica, native to the Sudan, produces "arabica" beans; and Coffea canephora, native to West Africa, produces "robusta" beans. About 2/3 of the beans in the international trade are arabica beans. They develop a more complex and balanced flavor than robustas. They also contain less caffeine, less phenolic material, and more oil and sugar. Robustas are only popular because the trees themselves are more disease resistant.
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