As published by The Caffeine Chaser.
Photo: Justin Coomber
There's nothing like waking up to the smell of fresh coffee, or walking into a coffee shop with that distinct coffee smell hovering in the air. The smell fills your nasal cavities and tickles all the way down to your toes, there's nothing more satisfying.
That aroma and flavor all trapped on the inside of a green seed, as we know it, the green coffee beans. It merely escapes with the roasting of these fascinating green beans. Roasting of green coffee beans brings out the aroma and flavor contributing to the distinct coffee smell and taste. Therefore, roasting plays a significant role in producing the coffee you would drink.
What does the process of roasting look like?
The roasting process generally takes place after the coffee has been processed from being picked.
In large operations, bags of green beans are either hand opened or machine opened. The beans are dumped onto a hopper where they are screened for the removal of the debris. These beans go to be weighed and is transferred by belt or pneumatic conveyors to the storage hoppers. They will be stored until they are needed to be conveyed to the roasters.
Roasters can make use of two types of roasting machines and they vary in size and capacity.
The oldest type of roaster is the drum roaster. Coffee beans are loaded into the drum or cylinder-shaped chamber that's lain on its side. While the drum rotates, either gas or electricity will be used to heat the tumbling beans inside.
The other type of roaster is the air roaster. This machine utilizes a rapid flow of super-heated air. The roast times depend on each roaster's unique experience.
The temperatures to which the beans are roasted varies between 180°C to 250°C at most. During the process of exposure to the heat, the beans will absorb the heat which is responsible for the color change from green/yellow to brown and increasingly darker shades of brown. These beans will continue to darken until removed from the heat.
Most roasters will use the combination of temperature, smell, color and sound to monitor the process of roasting. Sound is a very good indicator of the temperature during this process. Roasters will listen for a "pop" sound, just like the pop of popcorn, which indicates two temperature thresholds known as "cracks'. The first crack will emit at approximately 196°C which marks the beginnings of the light roasts. A large amount of moisture will evaporate and the bean will increase in size. The second crack emits at approximately 224°C which indicates that the structure of the bean is starting to collapse. When the beans are allowed to progress further, the beans will fully carbonize and eventually combust.
The beans are cooled directly after being roasted by a vacuum system or a water mist process also commonly known as quenching. Cooled beans will be packaged quickly, preferably in foil bags where the beans are allowed to degas.
Different levels and degrees of roasts:
The degree to which the beans are roasted is responsible for the different taste of the coffee in your cup. The level of roast preferred is subjective and depends on where you live. Most of us tend to think that the darker the roast, the stronger and richer in flavor our coffee, but the truth is that lighter roasts actually have slightly higher concentrations of caffeine.
The color of the roasted beans ranges from light to dark. Most roasters prefer to have specialized names for their favored roasts, but there's no standardization for roast names in the coffee industry. This can cause confusion when buying your favorite bag of beans, but in general the roasts fall under one of four categories which is; light, medium, medium-dark and dark.
The light roast consists of a light brown color, a light body and there will be no oil present on the surface. It's perfect for the tasting of origin flavors, as it's retained to a larger extent than darker roasts. Toasted grain taste and pronounced acidity is what makes the light roasts so unique. It retains most of the caffeine, therefore lighter roasts are preferred for those who need a strong cuppa. During the roasting process, the beans reaches an internal temperature which ranges between 180°C and 205°C. Usually at or around 205°C the first crack will be heard, which means lighter roasts are not roasted beyond the first crack, but just before. Common names that will appear are: Light city, Half city, Cinnamon and New England roasts.
This roast will be brown in color, with more body than the lighter roasts and an oil layer is still absent on the surface of the beans. The medium roasts start to lack the grain tastes of the lighter roasts, but it does exhibit a more balanced flavor, aroma and acidity. It is definitely stronger in flavor. Sadly, the caffeine is somewhat decreased but still higher than those of darker roasts. The beans will reach a temperature of between 210°C and 220°C, which indicates that the medium roasts exist between the end of the first crack and before the beginning of the second crack. Common names for the medium roasts are as follow: Regular, American, City and Breakfast roast.
Medium-dark roasts consists of a rich and dark color and the oils start to surface on the beans. It has a heavier body in comparison with those of the lighter or medium roasts. The distinct flavors and aromas of the roasting process starts to become noticeable, which is responsible for the bittersweet aftertaste. The taste becomes somewhat spicy. This specific roast takes place at the beginning or even in the middle of the second crack, which indicates internal temperatures between 225°C and 230°C. The common names are: Full-city, After dinner and Vienna roasts.
Dark-brown colors such as that of chocolate, or almost black, is evident in the dark roasts. A sheen of oil is visible on the surface of the beans, which is noticeable when brewing dark roasts. The flavors of roasting overpowers the origin flavors. Bitter tastes surfaces in this roast, which can be described as a smoky or burnt taste. The caffeine at this point has substantially decreased. Internal temperatures reaches up to 240°C, which indicates the end of the second crack. The beans are usually removed from heat at this point and seldomly reaches temperatures of 250°C. Dark roasts are commonly used for espresso blends. There's various common names for dark roasts, therefore it causes confusion. So make sure you check your bag of beans before buying. The common names are as follow: French, Italian, Espresso, Continental, New Orleans and Spanish.
In a nutshell:
Roasting changes the chemical and physical properties of a green bean and produces the characteristic flavor of coffee. When the green beans are being roasted, they are brought to rapidly high temperatures causing the beans to change in color and composition. The beans releases moisture and becomes crunchy and changes in color. The majority of the coffee is roasted commercially on a large scale. A small-scale commercial roasting became popular to "single origin" coffees served at specialty shops.
We are definitely ready to go bean shopping, and why not tell a friend a thing or two on your trip to finding the coffee that best suits your preference.
Till the next cup of coffee.
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