The term “espresso” is derived from the Italian word for express since espresso is made for and served immediately to the customer. A double espresso is a 47-62.5 mL (1.5-2 ounce) extract that is prepared from 14-17 grams of coffee through which purified water of 88-95°C has been forced at 9-10 atmospheres of pressure for a brew time of 22-28 seconds. The espresso should drip out of the porta-filter like warm honey, have a deep reddish-brown color, and a crema that makes up 10-30% of the beverage.
Espresso coffee brewing is defined by four “M’s”: the Macinazione is the correct grinding of a coffee blend, Miscela is the coffee blend, Macchina is the espresso machine, and Mano is the skilled hand of the barista. When each factor of the four M’s is precisely controlled, the espresso beverage that is produced is the ultimate coffee experience.
The best espresso should be extraordinarily sweet, have a potent aroma, and flavor similar to freshly ground coffee. The crema should be dark reddish-brown and smooth, yet thick. A perfect espresso should be enjoyable straight with no additives, yet bold enough to not disappear in milk. A pleasant and aromatic aftertaste should linger on the palate for several minutes after consumption.
The following steps describe in detail how to make espresso. You will also learn about the various factors and problems with espresso that limit its perfection. If any of these factors are off, you will not achieve a high quality espresso.
Roasting is a chemical process by which aromatics, acids, and other flavor components are either created, balanced, or altered in a way that should augment the flavor, acidity, aftertaste and body of the coffee as desired by the roaster.
The first stage is endothermic where the green beans are slowly dried to become a yellow color and where the beans begin to smell like toast or popcorn.
The second step, often called the first crack, occurs at approximately 205 °C (400 °F) in which the bean doubles in size, becomes a light brown color, and experiences a weight loss of approximately 5%. The corresponding Agtron number for this color is between 95-90 (Davids, 68-69).
In the next step the temperature rises from 205 °C to approximately 220 °C, the color changes from light brown to medium brown (Agtron # 60-50), and a weight loss of approximately 13% occurs (Davids, 68-69). The resulting chemical process is called pyrolysis and is characterized by a change in the chemical composition of the bean as well as a release of CO2.
The second step is followed by a short endothermic period which is followed by another exothermic step called the second crack. This second pyrolysis occurs between 225-230°C, and the roast color is defined as medium-dark brown (Agtron #50-45) (Davids, 68-69). The second pop is much quicker sounding and the beans take on an oily sheen.
Espresso potential is maximized in roasting when you maximize the sweetness and aroma of the coffee while minimizing the bitterness and acidity. Most people focus on the latter and therefore roast extremely dark, yet without sweetness and aroma the espresso will never be palatable. This explains the unpopularity of straight espresso and the popularity of espresso based drinks where either milk or other flavors are used to replace the sweetness that was lost by roasting darkly. So, if someone tells you that espresso needs to be dark and oily, don’t listen to them. The more coffee is roasted, the more caffeine is driven from the beans.
From 170-200°C the sugars in coffee begin to caramelize. From tasting pure sugar versus its caramelized component it is evident that uncaramelized sugar is much sweeter. The dark color of coffee is directly related to the caramelization of the sucrose in coffee. Therefore, to maximize sweetness you want to minimize the carmelization of sucrose, yet you do not want to roast too lightly or bitter tasting compounds will not thermally degrade. Stop the roast somewhere between the end of the first crack and less than halfway through the second crack. Do not roast far into the second crack. We recommend a roasting chamber temperature somewhere between 205-215°C. Realizing the danger of the following suggestion we might recommend a color similar to the one below. Note: All monitors, computers, and internet browsers will display the color slightly different. This is only a recommendation to point out that this color is preferable to the almost black color you will frequently observe for espresso. To get a better idea of roasting colors order the Agtron roasting classification kit from the SCAA.Contents courtesy Coffeeresearch.org