Primer For Coffee Roasting Levels

One of the great mysteries of coffee are the myriad of chemical reactions that occur inside the bean as coffee is roasted. Every coffee is different because they start with different bioflavinoids, esters and other complex organic compounds within the bean. But roasting then changes all these compounds at different levels. In fact, there is only one certainty when roasting – if you overdo it and burn the coffee all you are left with is charcoal. But even a very dark roast can still have some complex chemicals left within the bean, providing the flavor.

But there are some basic elements that change in the same way as coffee gets roasted. The most straightforward is caffeine itself. Caffeine is destroyed and broken down by high heat, so the darker the roast the less caffeine is left in the bean. Of course, starting caffeine levels differ from bean to bean, so that is just one element of the puzzle. But this explains why morning and breakfast coffees are usually light roast and evening and dinner coffees are dark roasts. The caffeine levels are adjusted to be more appropriate for the time of day.

In addition, light roasts tend to taste more earthy and more of a green and growing plant since more of the raw character of the bean remains behind. Dark roasts tend to taste of heavily roasted and cooked flavors like dark caramels or toast since part of the flavor does in fact include a burnt element.

So what goes on in the process? Coffee beans are the pit of the coffee cherry, a small red berry that growes on coffee trees and bushes. Coffee is usually hulled and dried near where it is grown so that the green coffee bean which is dry and resistant to rot and also very stable can be shipped. Then it is roasted before being delivered to consumers. In fact, roasting removes some of the stability and inert character of the green coffee bean and as a result means that roasted coffee beans can go stale and lose flavor. So roasting is best done shortly before consumption. Grinding roasted coffee accelerates this breakdown and means that ground coffee does not keep very long at all.

When a coffee bean is roasted it first dries out a bt, and then undergoes a process a bit like popcorn popping where steam from inside the bean builds up and breaks out, resulting in a very light popping sounds and also in an expansion of the bean in size. This process is called first crack and coffee is not considered roasted at all until it reaches this point. Before that happens the coffee bean changes color from a grey-green to a pale yellow to a light tan and then the depth and darkness of the brown color intensifies.

The color changes come from internal chemical changes as starches convert to sugar and begin to caramelize and burn. As the beans darken, a second cracking stage is reached, called ‘second crack’ and most coffee roasts are done to finish very close to this stage. Past the second crack, coffee reaches an internal temperature of 450 degrees Fahrenheit and at that point the combustion of sugars reaches a self-sustaining point and the coffee is irretrievably burnt.

As the coffee beans vent steam and expand they also grow lighter, losing water. Chaff (a thin outer skin) also comes off the bean continually between the first and second crack stages. This chaff is flavorless and doesn’t hurt the final coffee except to add a small amount of unnecessary bulk.

The art of coffee roasting lies in matching the original profile of coffee to the very small range of temperature and roast level between 410 and 445 degrees Fahrenheit that result in light roasts, light city roasts, full city roasts, italian and french roasts and all the myriad slight variations in between. Lighter roasts have more herbal, acidic flavors, darker roasts have more oily, smoky tastes. The same basic coffee bean can taste very different at different roast levels. And while at the very dark end of roasts, coffee flavors do tend to start to converge on the kind of taste associated with dark french roasts, they can still exhibit their own characteristics.

It is estimated that there are over 1000 bioflavinoid, sugar, ester and other volatile organic compounds in roasted coffee that contribute to the overall flavor. So it is worthwhile to experiment and look for the kinds of flavor you like.

Roast Levels

• Light – as first crack is underway – lowest drinkable roast level, very low in body and high in acidity. High in caffeine. Used only by high-volume commercial operations.
• Light city – also known as American – end of first crack. Coffee is now clearly brown and flavors are starting to develop. Common roast level for high-volume operations.  From here to the next official roast level, you get usage for breakfast roasts and blends.
• City – beginning of second crack – also known as medium – roast level for medium gourmet coffees and a pretty common choice for balance of flavor and strength.
• Full city – midway through the second crack – this is also known as Viennese – and is the last stage before the darker burnt flavors start to develop. From here on out timing is critical since from here to burnt can be as little as a minute.
• Italian – just at the end of second crack – first of the dark roasts – popular after dinner roast level.
• French – second crack is clearly over but there is a very small difference between Italian and this level. The darkest roast level that is common. Some roasters make a dark French which could also be called lightly burnt…
• Burnt – yep – that’s the next stage.

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1. Roasting Coffee – the Basic Way