Coffee: Roasting.

Madison.

Coffee: the roasting process. You could, conceivably, find an alternate use for green coffee beans,¹ but, as Harold McGee writes: "Raw green coffee beans are as hard as unpopped popcorn, and about as tasty."

Coffee roasting turns these little green BBs into brown, brittle packages, developing their flavors through a careful application of heat. Anyone can do it at home, though a frying pan or a modified popcorn air-popper does lack some of the subtle control that the professional drum roaster offers. In general, the process goes like this, regardless of your choice of roasting apparatus:

1. The roaster heats the green beans over a fairly high heat. They're endothermic at this point, absorbing heat as their temperature increases. Slowly, they'll begin to change color from gray-green to a dull yellow and take on a faint aroma of hay, around three minutes².
   
   
2. The beans continue to change color and aroma, from yellow/hay (three to five minutes) to gray-brown/bread (six minutes) to cinnamon/coffee (eight minutes) - and they begin to expand as the remaining moisture vaporizes, puffing up the beans. Throughout this process, an experienced roaster can smell the beans to gain an sense of the flavors that will be present in the final roast. In the even you're considering this as something to try at home, beware that the beans will start smoking here. A lot. All of the bean's proteins, sugars, phenols, etc., start to break down, producing all of the great variety of coffee flavors and aromas, while giving off lots and lots of smoke. (Invest in a really good ventilation system, or do it outside.)
   
   
3. At about nine minutes, the beans reach the "first crack", which is the point where the chemical breakdown becomes self-sustaining and the beans become exothermic (about 320°F). Since they're putting off energy, the roaster needs to reduce the heat to avoid burning the beans, which will give them a harsh, unpleasant flavor. The first crack is where the steam pressure inside the beans causes them to pop, with a sound a lot like popcorn, starting with a few sporadic beans before it suddenly erupts in a wave of popping sounds.
   
   
4. Depending on the hardness of the bean, which is primarily a function of altitude - beans from lower altitudes are considered "soft", and can't take as much heat without burning - the roaster may then choose to apply extra heat to finish the roasting. At about twelve to thirteen minutes, the beans will enter the "second crack", which is where the natural sugars begin to caramelize. It sounds very much like a series of small cracks, as the beans themselves deform enough to produce small cracks or, in some cases, break pieces off.
   
   
5. When the beans have reached the desired level of roast, the roaster cools them down with a flow of cold air, usually stirring the beans to bring them down to room temperature as quickly as possible to stop the roasting process.

There are an unbelievable variety of final roast levels, and no one really seems to have agreed on what "dark roast" and "espresso roast" mean, exactly. Part of that is due to the fact that different styles of roasting - the subtleties not mentioned in the above that give each roaster their signature flavors - give varying end results within the "medium-dark-French" roast range. Here's one approximate breakdown of some typical roast levels you might see:

• Light roast. This would be any roast that never made it to the second crack, and you don't see them often. The aromas are often underdeveloped at this point; the coffee's natural sweetness is subdued; and the coffee's acidity is very high and often unpleasant.
  
  
• Medium roast. A medium roast should be the best expression of a coffee's character, with the roasting stopped just as it reaches the second crack. At this point, the aromas and flavors that are part of the bean itself - as opposed to the flavors of the roast - are fully expressed, and haven't been driven off by further roasting. A high-quality coffee will be naturally sweet at this point, but coffees with defects - meaning 98% of the coffee out there - will have varying degrees of bitterness that make them unpleasant.
  
  
• Dark roast. A dark roast coffee has usually been roasted until the second crack is nearly complete,³ but not quite. The Maillard reactions produce more sugars, resulting in a sweeter coffee that can disguise the bitterness of mid-grade beans. It also produces more flavors of the roast, such as toast, cooked beef, and roast coffee.⁴ The downside is that many of the delicate, complex aromas have already started to disappear, though there are some coffees that benefit from a darker roast. A small amount of natural oils may appear on the surface of the beans.
  
  
• French roast. This roast has pushed all of the way through the second crack, resulting in a coffee with intense roast flavors and very little, if any, of the bean's aromas remaining. The telltale aroma of a French roast is maple syrup, though there are often notes of toast and smoke, especially as the coffee runs the risk of burning by this point. Ruptured cells start leaking oils to the surface of the beans, giving them a definite gloss. There is also a significant amount of caramelized sugar⁵, as well as the creation of new, harsh flavors from the Maillard reactions. The high sugar content of French roasts makes them good candidates for the high-pressure, short-time extraction used in making espresso.
  
  
• Italian roast. Just short of completely burnt, this is a roast sometimes used for espresso. There are no real aromas left, and the development of harsh, bitter flavors overwhelms any developed sugars. The distinct aroma of an Italian roast? Fish.

In addition to roast level, roast date is a critical piece of information in finding good beans. The roasting process develops enormous amounts of carbon dioxide, which the beans expel over the next several days. Enough that it's all but impossible to keep them in a completely closed container; any sealed bag of coffee will have a small, one-way air valve to let the excess gas escape, pre-explosion. Though this does prevent staling due to oxygen, the production of carbon dioxide helps volatilize the delicate oils that give the coffee its distinct aroma, so its quality begins to fade away quickly.

Coffee is best when made one or two days after roasting, when the aromas are still present. It'll still be good, without any noticeable stale flavor, for at least ten days after roasting. Grinding, however, greatly accelerates the staling process, and you can notice a definite loss of flavor in just a few hours. Ground coffee will stale in just a few days.

In case you're interested in home-roasting, you can give it a go with anything from a cast-iron skillet to a countertop roaster, which is like a miniature version of the gas-fired drum roasters used by professionals. Check out Sweet Maria's for a good selection of high-quality stuff, including better green beans than you'll find just about anywhere else.⁶ Just want to buy some good beans? Get 'em from Sweet Maria's or Johnson Brothers Coffee Roasters.

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¹Like in Brazil in the '70s, when they were strongly considering the use of low-grade beans - most of Brazil's crop makes harsh, thin coffee - as fuel for steam locomotives.

²The times here are estimates, assuming you want to finish the roasting process in about twelve to fifteen minutes. Less than ten minutes produces sour flavors, while longer than twenty gives the coffee a baked aroma. A good roaster adjusts the heat applied throughout the process to, ideally, bring in every medium-roast batch at the same time.

³Better sorted - i.e., more uniform - beans will tend to reach the first and second cracks as a group, relatively close together, but it's still a period that stretches over thirty seconds or a minute, depending. Less uniform batches of beans run the risk of over- or under-roasting portions of the coffee, resulting in a mess of off-flavors.

⁴This is not a joke. Roast coffee is a standard aroma in coffee, and is present in all roast levels, but at different amounts. It also tends to be one that remains in coffee over time, after all of the other aromas have dissipated.

⁵The reason this roast was developed and is so frequently used is that the high development of sugars covers the natural bitterness of coffee defects. It also allows larger roasters - particularly the big corporations - to maintain a more consistent product, since variations among French roasts are far less than among medium roasts.

⁶You're paying well above normal green bean prices, for the privilege of having access to Tom Owen's pre-approved selections. Every coffee he'd sell you is one that he's already roasting and selling, himself.