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.
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