The mystery of coffee roasting is exposed

The mystery of coffee roasting is exposed

How many distinct coffee roast varieties have you heard called by? What about light, medium, or dark? Espresso? Continental? Wien, Francais, Italiano, Espaol? City? Full-City? Who comes up with these ridiculous ideas?

The dirty little secret (excuse the pun) of the coffee business is that there isn't universal agreement on how to classify different roasts. Therefore, we are all free to shop around, sample coffees from various vendors, and settle on our preferred blend(s). In this piece, I'll make an effort to employ common terminology and relate that terminology to the color and texture that any reader may evaluate for themselves.

Green coffee beans are the first step in the roasting process. These are kept at 12–15% humidity at room temperature. Temperatures of 450 degrees Fahrenheit and above are used for roasting. Roasting depends on both time and heat.

Heat can be absorbed by a coffee bean until its internal temperature reaches between 212 and 240 degrees Fahrenheit. At this stage, the bean's exterior will begin to darken into a lovely cinnamon shade. At this point, the bean will begin to steam.

As the bean continues to cook (between 250 and 300 degrees Fahrenheit, again depending on the type), the outer membrane dries out and begins to peel away from the bean. The bean experiences a 'first crack' when the temperature rises above 350 degrees Fahrenheit. This split opens as internal moisture escapes through the bean's preexisting gap. As a result, the leftover bean "chaff" is blown out of the little opening.

Coffee has reached the "light city roast" stage when it turns a light brown. The sugars within the bean begin melting, or "carmelizing," at temperatures just above 370 degrees Fahrenheit, the typical range for a city roast. It's this process that produces the classic 'coffee brown' hue. Around 400 degrees is where most city roasts are turned off. In this stage, the sugars are not fully caramelized, and the origin of the beans is more important than the degree of roasting in determining the flavor.

At higher temperatures, when the bean has reached the "second crack' stage, the "full city roast" stage begins. Depending on the bean variety, this process may take place at a range of temperatures. The second split occurs when the bean's internal temperature reaches the point at which its cellular makeup begins to degrade. The full city roast is achieved by stopping the roasting process at the precise moment the second crack appears (between 425 and 435 degrees Fahrenheit). The bean has darkened in color but still has a "dry" appearance, as the molecular breakdown that releases the bean's oils has not yet begun.

As the coffee continues to roast, it will enter the second crack and progress through the Vienna, Continental, French, and/or Italian roasts. The term "Espresso Roast" is also used to describe these, although technically this term does not exist. It's true that not all Italian espresso blends are the same; for example, the 'Vienna' roasting stage, far into the second crack, is typical of northern Italian espresso blends. At this point, the sugars within the bean have almost completely caramelized, and many beans within the roast will appear dark brown with indications of cracks. Most espresso mixes in southern Italy are roasted to the "French Roast" stage, where the beans are uniformly dark brown and just a shade or two from being completely black and where oils are beginning to emerge from some of the beans.

Beans roasted past this point will start to smoke heavily as they give off their oils and soluble components, but they will still turn out pretty dark with a very oily sheen. They can be designated "Italian Roast" if they haven't completely burned. Since I've found that the internal roasting temperature for each of these stages varies with the type of bean being roasted, I rely more on my senses than the probe thermometer when the roasting process reaches the second crack.

When coffee beans are roasted past the first crack, they no longer retain their varietal tastes. Is that something to be concerned about? Okay, maybe for some people... And early on in my roasting career, I almost grieved when a batch of premium Puerto Rican pick wandered unattended into the Italian roast domain before I managed to get back to it and rescue the special taste notes before they were lost. However, the characteristic French roast stage favors some kinds. Cup results should not be contested on the basis of personal preference; de gustibus non disputandum est.

And that's how you roast your coffee. There seems to be a lot of "slow-roasted' and 'deep-roasted' coffee advertised, and it makes me wonder what the difference is. Yes, I believe it would be a lengthy procedure to roast a large quantity of beans in a cool oven. If a roaster wants to get his beans to a specific level of doneness without burning them, he needs to be accurate and not roast them too quickly. But I wouldn't want to take any longer than necessary, intentionally.

What exactly is "deep" roasting? Hmm. I'm not sure what a "shallow roast" is, but I imagine it's the polar opposite of a "deep roast." The only 'secret of the trade' I can think of is counterintuitive to the idea of keeping beans at a constant temperature: once a batch reaches the desired degree, remove it from the roaster immediately and cool it down rapidly. It is crucial that the sugars and soluble components within the bean get 'boiled' very specifically, as explained above, to ensure a high-quality roast. Beans will continue to cook if kept in a hot environment (yes, even with other beans nearby, which will give off their own heat energy).

This is unavoidable to some degree, but a skilled roaster will make up for it by understanding his roasting environment and, ideally, setting up a cooling area where the beans may cool as quickly as possible by being exposed to cool (i.e., room temperature) air. This "coasts" them into their final, distinctive hue and flavor.