Getting to know the secrets of coffee roasting

Coffee roasting, one of the most important and most important processes that coffee goes through before it comes to our cup, has such deep roots in time as the coffee itself.

Though roasting, green coffee beans lose the moisture they contain and unfold the characteristic aromas of coffee. Although the chemical composition and nutrients contained in a roasted coffee bean do not differ substantially from those in a green one, what is decisive is the flavor and aroma - the well-known taste of coffee would not be possible without roasting.

The devices currently used for coffee roasting are divided into cylinder machines and hot air machines. On cylinder machines, the grains are roasted on a rotating heated surface, while in air machines, roasting is done in a pipe from which hot air passes through.

In both cases, roasting requires high temperatures while the overall process rarely exceeds 15-20 minutes, depending on the equipment used and the desired degree of roasting. Roasting is a process that requires knowledge and experience in order to make coffee beand unfold the desired flavor. Roasting is a multifactor method, which is influenced by temperature, time, and speed of the machine rotation (or air volume for air engines). Nowadays, the roasting process has turned into science, for which precision thermometers and sensitive timers are usually uses, as well as much experimentation in order to reach the desired result.

Until the recent past, the roaster’s experience and “hand”  played a decisive role. Roasting depended on the two “cracks” that can be heard during the process: the first crack (due to the release of moisture and oxygen) means the beginning of the light roasting phase, while the second crack (the release of carbon dioxide) signaled the passage of the grains into dark roasting. Choosing the right roasting tone was done with the smell, but also by counting seconds after the sounds were heard. Despite advances in technology, these methods, based on many years of common experience, are still in use.

What are the different roasting deegrees ?  

• Light Roasting (196^oC - 205 ^oC) : The bean’s color varies in light tones of brown. The coffee has  strong acidity, its natural flavor characteristics (those that depend on its variety, climatic conditions, its method of processing) are particularly intense, while other characteristics such as sweetness have not yet been developed.
  Medium Roasting (210 ^oC - 219 ^oC) : Coffee beans color darkens, while the acidity gradually decreases. The natural flavors of coffee remain intense, while the flavor is enriched by the roasting process. It is a widespread roasting degree, both for commercial and specialty coffee.
• Dark and Very Dark Roasting (225 ^oC – 245 ^oC) : Coffee beans color darkens more, ranging from dark brown to glossy black, (in very dark roasting). Coffee acquires caramel notes and bittersweet aromas. As the roasting degree gets higher, natural taste declines in favor of roasting, burnt like aromas.

Interesting Roasting Facts : 

• The oldest surving roasting machines are made of metal or porcelane and are, more or less, flat pans with large handles. Dating back to 15th century, they originate from Ottoman Empire.
• The first cylinder machine, which allowed coffee beans to move and looked quite similar to the current machines, appeared in Cairo in 1650 and spread rapidly throughout Europe.
• Until the middle of 19th century, most of coffee lovers used to roast coffee beans in their home kitchen. Selling roasted coffee beans was not as usual and popular as today. 
• There are various strange roasting techniques around the globe. In Vietnam, beans are sometimes roasted with butter and sugar, a process that ends in coated coffee beans with caramel flavors. 
• Roasted coffee beans have to rest and mature for some days to be ready for grinding and extraction. During these days, they lose CO2, something that affects coffee's taste and characteristics.
• Contrary to popular belief, the roasting degree does not affect caffeine content ! 
• The thee basic roasting deegrees described have many other sub-deegrees, with "cinammon roast" being the lightest and "Napolitan roast" being the darkest.