1. Discoloration – Color Changes
Although the seeds decrease the quantity of water at the same rate throughout the roasting process, the initial stage of the roasting process is often referred to as the “drying phase.”
The chlorophyll degradation leads the seeds to change color from blue to yellow within minutes after roasting the head. The Maillard process causes the roots to change color from yellow to yellow and eventually brown as they burn. The brown hue of the seeds will darken when they reach the first crack owing to the caramelization process. Carbonization may become black during dark roasting.
2. Classic Definitions of Roast Degree
During the preparation for the French roast, these seeds are photographed every 1p. The seeds change color from yellow to tan, then brown, and if coffee beans are roasted long enough, extraordinarily dark and black. There is no standard method for identifying various roasts; one roaster calls a light roaster, and another calls a full-city roaster.
Light roasts include fruity, flowery, acidic, and more delicate tastes than dark roasts, as well as a more petite body. Smoky, pungent, bitter, and carbon tastes are produced by DR. When roasted to a high degree, the fire flavor takes over, and the body diminishes.
The lack of agreed-upon nomenclature regarding roasting levels in the coffee business generates misunderstandings among roasters and consumers. I don’t claim to have the definitive definition for various roasting degrees. Still, I feel the descriptive titles below indicate a broad and reasonable interpretation of roasting levels and roasting green coffee colors.
Roast-style cinnamon is often “dropped,” released from the roasting cage early in the first crack. Some drinkers prefer green, grass, and bean variants. However, some more prominent organizations that sell coffee beans to consumers concerned about pricing prefer the cinnamon roasting method since it results in less volume loss.
Sour, generally “green” or “peanutty,” with grassy and flowery notes and a light body in the cup.
Particles released at the last stage, or only later, first crack, are called roast at the city level. Roast for a light-bodied coffee with a high acidity level. City roasts are presently popular among progressive or third-wave roasters, and they used to be the standard in Nordic nations.
Acidic, winey, sweet (mainly fully developed), and juicy in the cup, with flowery and fruity aromatics, a touch of caramel, and a light body. It may taste grassy, lemony, and sour if not completely matured.
2.3. Full City
“Full City roasts” are roasts that discharge right before the second fracture and the emergence of the oil surface. Whole city roasts are popular among customers because they provide a unique blend of mild acidity, mellow caramels, and medium body.
Caramelly, with ripe fruit and a medium body in the cup.
Viennese roasts are coffee beans that have been released during the early phases of the second crack when the fresh oil has begun to rise to the top. Starbucks’ average roasting level is an excellent example of the darker Viennese. Bittersweet, caramel, fragrant, and often nutty or spicy in the cup, with a thick and syrupy texture.
Oil-filled coffee beans with intense, bittersweet, and carbonized characteristics are French roast. Because of the dark roasting, it isn’t easy to discern the unique features of coffee bean roasters.
Burnt, bitter, and smokey with traces of caramel in the cup; the body may be bold or medium since the body is most vital at a lighter French roast and lowers as the roast progresses.
Italian roasters produce medium roast coffee, but the blackest, oiliest, bitterest, and most carbonized roasting degree has become commonly recognized as Italian roast.
Because the disintegrating cellulose structure enables rapid oxidation and loss of flavor, almost all Italian roasts have a foul odor (rancid) until the coffee beans are eaten. Burnt, smoky, sour, and carbonized in the cup, with a medium body.
3. Structural Changes
The coffee filling has a well-organized and solid structure, with oil coating the cellulose matrix’s surface. When coffee roasts, the pressure within the grain rises as vapor and CO2 are produced, causing the grain structure to expand and the hole to grow. The seeds begin to release silver-colored skin, or chaff, a few minutes before 1st crack and trap it within the folds of their central fissures.
When cellulose can no longer dilate, cracks develop within and on the particle’s surface, allowing steam and vigorous gases to escape, resulting in the popping sound of the first break.
Specialty roasters want a light or medium roast that discharges the grain between the end of the first crack and the beginning of the second crack. The gas generation continues after the first fracture, replenishing the pressure within the particle cell. The granular structure becomes increasingly brittle at the same time, preparing for the second fracture.
While the rise of steam pressure is the original cause of the first fracture, the accumulation of CO2 is the primary cause of the second break. The oil escapes to the grain surface just before or after the commencement of the second crack; almost all roasters will pay attention to this as an objective signal of the dark roast’s target temperature.
In the second crack step, the seeds are released. Keep an eye on the oil’s surface and fissures.
4. Inner-Bean Development
Throughout the two cracking phases, particle expansion and drainage of steam and gases degrade the cellulose structure of the particles, making them hollow and brittle. The grain is darker, hollower, crunchier, and more developed on the inside. For optimum crushing quality, multiple/high glass extraction, and the elimination of unwanted savory tastes, proper seed development is required.
During roasting, the development within the seeds lags behind the growth outside the grain. A roaster’s process abilities must be managed to guarantee that the interior of the grain is sufficiently roasted until the exterior of the grain achieves the desired color.
The final spread, or color difference, between the inner and outside grain should be minimal for light-roasted coffee beans. The darker the roast, the greater the color difference, allowing the grain’s insides to expand to the minor extent possible. I will explore ways for improving grain growth throughout the book.
5. Coffee Beans Size, Density, and Weight Loss
When roasted, the coffee loses 12-14 percent of its weight, depending on the moisture content at the start, the roasting phase, and the development of the seeds throughout roasting. Sources discharged during the last stages of the 1st crack and lost the average volume, or shrinkage-contraction, in the range of 11-13 percent may provide the lightest delicious roasts.
Shrinkage is about 14-16 percent 30 seconds after the first crack stops and around 17-18 percent at the commencement of the second crack. Black roasting oil may have a percentage of 22 percent or higher. The presently popular light roast loses 14-16 percent of its original weight in the specialty business.
Water contributes to up to 90% of weight loss in mild roasts. The remainder is organic stuff, mainly CO2, with minor quantities of trash, CO, N2, VOCs, and volatile acids thrown in for good measure. Organic matter loss rises dramatically with dark roasting: OM loss ranges from 5-8 percent in medium rin roasted to 12 percent in highly dark roasts.
They lose weight when seeds are roasted and hatch to 150-190 percent body of their original volume. The simultaneous weight loss is comparable to a half-density decrease.