Coffee and espresso start with the same green coffee beans, but the ensuing processing and preparation produce different styles of brew. Espresso concentrates the essence of coffee, with a flavor deeper and more intense than regular drip brew. This explains the difference in serving sizes: Espresso typically comes in a 1.5-ounce demitasse cup, while brewed coffee is served in a 6- to 8-ounce mug.
Any green coffee bean can be used for either drip brew or espresso, but roasters use some best practices:
Espresso blends often feature Arabica beans due to their superior quality. The beans are roasted until they take on a medium to dark brown color. The range of bean options and roast profiles for drip brewed coffee is wider than that used for espresso. Drip coffee can be made from light, medium or dark roasted beans. Lighter roasting allow you to experience more of the bean's natural flavors, while darker roasts highlight the caramel and toasty notes of the roasting process.
Once the beans are roasted, the coarseness of the grind determines the type of coffee you can prepare.
- Espresso requires very finely ground beans that can be compressed into a puck in the basket filter. A coarser grind, such as that needed for drip brew coffee, would not allow the hot water to extract flavor under pressure.
- Drip brew coffee needs a medium coarseness. This gives enough surface area for hot water to extract flavor compounds but not so much that coffee dust ends up in your finished beverage.
The most important difference between coffee and espresso comes during the brewing process. Espresso is made by forcing hot water through a compressed puck of finely ground coffee at high pressure. This process produces an intensely flavored viscous shot of coffee topped with a lighter-colored foam called the crema.
Brewed coffee is made by allowing nearly boiling water to slowly filter through ground beans until it drips through a filter into a pot. This method can produce larger quantities of coffee at a time than espresso.
The beans used to brew espresso and drip brewed coffee contain about the same amount of caffeine although the resulting beverages vary widely.
A 1.5-ounce serving of espresso contains 77 milligrams of caffeine. An 8-ounce cup of coffee contains 163 milligrams -- more than double the amount in a shot of espresso. But if you compare an ounce of espresso to an ounce of brewed coffee, the espresso has 51 milligrams per ounce compared with a mere 20 milligrams per ounce in brewed coffee.