Viennese

Viennese roasts are those dropped in the early moments of second crack, when oil has just begun to migrate to bean surfaces. The standard roast degree offered by Starbucks Corporation is an example of a darker Viennese roast.***

In the cup: Bittersweet, caramelly, pungent, and often nutty or spicy, with heavy, syrupy body.

Left: French roast, Right: Italian roast

French

French roast indicates oily beans with pungent, bittersweet, and carbonized flavors. Such a dark roast makes it difficult to detect a bean’s unique character.

In the cup: Burnt, bitter, and smoky, with hints of caramel; body may be heavy or medium, as body peaks at a lighter French roast and declines with further roasting.

Italian

Most Italian roasters drop their coffees at medium roasts, but somehow the darkest, oiliest, and most bitter and carbonized roast level has come to be known as Italian roast. Almost all Italian roasts are rancid by the time they are consumed because their degraded cellulose structures allow rapid oxidation and staling.

In the cup: Burnt, smoky, rancid, and carbonized, with medium body.

Structural Changes

The microstructure of green coffee is relatively organized and dense, with oils coating the cellulose matrix.¹⁰ As coffee roasts, the generation of steam and carbon dioxide (CO₂) increases pressure within the beans, forcing their structure to expand and pores to enlarge. A couple of minutes before first crack, beans expand enough to begin freeing the silver-colored skin, or chaff, trapped within the folds of their center cracks. When the cellulose can stretch no farther, fissures form within beans and on their surfaces, violently expelling water vapor and gases, creating the popping noises of first crack.

Specialty roasters seeking a light or medium roast typically drop beans between the end of first crack and the beginning of second crack. After first crack, gas production continues, rebuilding pressure within the bean cells. Simultaneously, the bean structure becomes more brittle, setting the stage for second crack. While the primary cause of first crack is the buildup of steam pressure, accumulation of CO₂ is the main driver of second crack. Just before or after the onset of second crack, oils bleed to the bean surfaces; almost all roasters would regard this as an objective indicator of a dark roast.

Beans dropped during second crack. Note the surface oils and fissures.

Inner-Bean Development

Bean expansion and the release of water vapor and gases during the cracking phases weaken beans’ cellulose structures and make them more porous and brittle. The darker, more porous, and more brittle the inner beans are, the more developed they are. Sufficient inner-bean development is a prerequisite for great grind quality, high extraction, and elimination of undesirable savory flavors.

Inner-bean development lags behind outer-bean development during roasting. A roaster must skillfully manage the process to ensure that the inner bean is sufficiently roasted by the time the outer bean reaches its intended color. Ideally, the final “spread,” or color difference, between the inner and outer bean should be negligible in a light roast. The darker the roast, the larger the acceptable spread, provided the inner bean has developed to a certain minimum degree. Throughout this book, I will discuss strategies to optimize inner-bean development.

Bean Size, Density, and Weight Loss

Coffee loses 12%-24% of its weight during roasting, depending on initial moisture content, roast

degree, and inner-bean development during roasting. The lightest palatable roasts are probably those dropped during the latter stages of first crack and typically have weight loss, or shrinkage, of 11%-13%.**** About 30 seconds after first crack ends, shrinkage is roughly 14%-16%, while at the onset of second crack, shrinkage is around 17%-18%. Dark, oily roasts may have shrinkage of 22% or more. The light roasts currently popular in the specialty industry lose an average of 14%-16% of their initial weight.

In a light roast, water accounts for up to 90% of the lost weight. The rest is organic matter, primarily CO₂, as well as small amounts of chaff, carbon monoxide, nitrogen, volatile aromatic compounds, and volatile acids. Organic losses increase significantly with darker roasting: Organic-matter loss is 5%-8% in medium roasts and as high as 12% in very dark roasts.⁵ As beans lose weight during roasting, they also expand to 150%-190% of their original volume. The simultaneous loss of weight and gain in volume equates to a density loss of almost half.

The trowel allows a roaster to sample beans during a roast.

* “Cinnamon” relates to the color of the beans at this roast level and has nothing to do with the flavor of cinnamon.

** Coffee importer Timothy Castle coined the term “third wave” in 2000 in reference to a movement refocusing on coffee quality. Castle described the first wave as the emergence of pioneering, quality-obsessed coffee entrepreneurs in the 1960s, ’70s, and ’80s who offered the first modern alternatives to large, institutional roasters. The second-wavers were a group of skilled businesspeople in the ’80s

and ’90s who offered quality coffee but were more business savvy and profit oriented than the first-wavers. The third wave developed as a rebellion against the compromises of the second wave and offers a renewed commitment to coffee quality. Common usage of “third wave” has evolved away from Castle’s original definition and now typically refers to companies favoring lighter roasts and brewed-to-order coffee made by hipsters.

• I think of full city and Viennese roasts as the “crowd pleasers,” though most connoisseurs and third-wave companies frown upon such roasts. Critics contend that a lighter roast highlights a bean’s uniqueness, while a full city or darker roast blunts too much of a coffee’s acidity and delicacy.

• These estimates assume a green-coffee moisture content of 10%-12% and a roast time of 11-12 minutes. Actual shrinkage may vary considerably.