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Let's Talk Coffee, Part 2: Roasting


Wed, 14 Mar 2012 «permalink»

Last time on let’s talk coffee, we talked about the process of harvesting and processing coffee beans, as well as the effects of geography, environment, and cultivar on flavor profiles. Today, we’re going to talk about…

Roasting

After beans are processed and separated from the fruit, they need to be roasted.

From left to right, unroasted green coffee beans to dark roasted coffee beans.

One thing that many people don’t realize about coffee is that in spite of it being a “dried good” it does have a short shelf life for quality. Coffee beans emit CO2 after being roasted. This is why many whole-bean coffee bags have a one-way valve on them; to allow for off-gassing. This is only a prevalent interaction for a few days after roasting, but continues for weeks. The displacement of the gasses contained in the beans allow for oxygen to enter the bean. Oxidation of the oils and aromatics lead to the coffee becoming stale, and when the complex flavors of the bean have died you are left with the bitter, chalkboard coffee that so many people dread. Worse than stale beans are pre-ground beans. Once a bean is ground, the increased surface area leads to an almost immediate off-gassing of all the CO2 and the oxidation process beings immediately; no amount of freezing or packaging can keep ground coffee from going stale. We’re going to discuss a little bit of the roasting process today, so you can get a handle on why fresh is important when it comes to great coffee.

Roasting, Caffeine, & Flavor

Lighter and medium roasts tend to preserve more of the flavor profile of the bean as it has inherited from its sourcing. This leads to a tastier cup of coffee, but also a more fickle cup of coffee that takes more effort to brew well. Darker roasts tend to develop flavors that are characteristic of the roasting process and not the bean themselves; these flavors present consistently across brews, but many coffee “snobs” tend to prefer the flavors of the bean over the flavors of the roast. Because extremely dark roasts have flavors that are more characteristic of the roast and not the bean, dark roasts are often used commercially to make a product that doesn’t taste shitty when it gets too old or is brewed using drip machines and such. This is Starbuck’s secret to success; they go nuclear on their beans and mostly eradicate the profiles of the beans in favor of a consistent roast that they can sling out in their giant perc-o-vats. I’d even make the argument that objectively, Starbucks blatantly over-roasts their beans beyond recognition.

Roasting also has an impact on the caffeine content of the bean. Darker roasts contain less caffeine. This flies in the face of the common convention that espresso has more caffein than traditional coffee. First and foremost, there is no such thing as an espresso roast. Espresso refers to name of a drink that is created by a specific brew and extraction method. Most beans prepared for espresso tend to be of a very dark roast. As such, there is actually less caffeine in a dark roast bean than in a light roast bean; the high caffeine content in a shot of espresso comes from the fact that the espresso is a concentrated extraction. Taking an off-the-shelf “espresso roast” from the grocery store and brewing a regular cup of coffee from it will yield a lower caffeine cup than a lighter roast.

Home Roasting

Because green coffee beans can stay fresh for years but roasted beans can lose their characteristic flavors in a matter of weeks or months (especially lighter roasts), some people choose to undertake the process of coffee roasting at home to ensure that they get the freshest tasting coffee possible, preserving as many of the complex aromatics and essential oils with a light roast without worrying about the age of the beans compromising these flavors. It also allows a coffee lover to buy green coffee beans and then roast small volumes at a time so that every batch of coffee is fresh and tasty.

Home roasting can be done simply in a frying pan, or using more complicating setups including a rotating drum over a heating source. Stovetop roasting is imprecise, since its difficult to evenly roast all of the beans just through the process of “jumping” the pan or stirring with a utensil. Most coffee roasting machines use some sort of indirect heat or mechanical mechanism like a spinning drum to more evenly roast the beans. The particular point in time in the roasting process is often gauged by “cracks”, that is to say cracking noises made by the beans similar to popcorn. “First crack” occurs at the beginning of the light roast spectrum, and “Second crack” refers to the beginning of the medium roast spectrum. Roasting also produces a lot of smoke and whatnot, and needs excellent ventilation. Precise environmental factors, specific temperatures, and other factors all have an effect on the flavor imparted by the roast. It isn’t easy, and it isn’t a hobby that I’ve picked up yet, but it’s something that I look forward to trying out one day soon when I get around to building an outdoor coffee roaster.

I’m Not About To Start Roasting My Own Coffee…

Nobody expects you to, but you should definitely take the effects of roasting and staling in to consideration if you want the best cup of coffee you can get. Try to locate a local coffee roaster where you can get fresh roasted beans so you can ensure that they are young enough to not have oxidized too much. I’ve frequently heard the rule of thumb to be that grean coffee is good for 2 years, roasted beans for 2 weeks, and ground beans for 2 hours. Here in Northwest Florida and Lower Alabama, Keen’s Beans is a good source of fresh roasted, single-origin Costa Rican Arabica beans that are dry-processed in the sun. They sell grean beans, and fresh beans that are roasted immediately prior to shipping; this is why they only serve Florida and Alabama (freshness, remember!). You can buy them all over Pensacola; I stock up on beans every time I snag groceries at Apple Market. It’s not the greatest choice for beans without roasting yourself, but it’s still miles ahead of any cruft I could pick up (whole bean or not) from Publix.

Intelligentsia also does a good job of roasting beans immediately before shipping if you don’t have a roaster near you, and they serve the entire US. They carefully schedule the roasting and production of their coffee so that it gets to you as fresh as possible. But it’s still no substitute for a local roaster. Remember, a roaster can source their green coffee beans from nearly anywhere so you don’t need to be around a huge operation to get high quality beans. Take some time to do some research, and you won’t be disappointed.

Next time on Let’s Talk Coffee: Brewing and Extraction!