The roasting of coffee is decisive for the approximately 800 aroma substances that determine the taste of the coffee. A range from dark chocolate and roasted peanuts to fruity wild berries can give the coffee its unique aroma.
Why Do Coffee Beans Need To Be Roasted?
Only by carefully roasting the cleaned and dried coffee beans, the aromas, flavors and texture that make this beverage so unique, unfold all the way.
If you ever saw a freshly picked coffee cherry before, you know that these cherries do not have much to do with the dark, aromatic beans we normally put in our espresso cooker. After extracting the beans from the cherry, freeing it from its various skins and drying it, bright, pale coffee beans remain. These raw coffee beans often contain chlorogenic acid to and extend that causes them to be somewhere between inedible and unhealthy. When exposed to heat, a lot of this acidity can be removed and the extensive flavors unfold during the Maillard reaction.
Also, raw coffee beans contain more water than roasted coffee beans. In order to actually brew a coffee, the ground beans cannot be saturated with water, otherwise they wouldn’t soak up the boiling water and none of the aromas could be extracted properly.
Depending on the condition of the raw coffee and the demands on the final product, various different roasting methods can be used. Today, there is just as many posting recipes as there is varieties of coffee. Now, more than ever, roasting coffee has become a real craft and has become a popular trade not just in Italy but in many other countries too. #
The Roasting Process
The raw coffee is exposed to a dry heat between 180 °C and 230 °C inside a furnace. In order to reach a uniform roast and to prevent burning the beans, the beans are continuously stirred and turned. Normally the beans remain inside of the oven for about eight to twenty minutes, undergoing various roasting cycles. By purposely moving the air inside of the furnace, different, smokey aromas can be added to the beans. Additives are not used during the roasting process.
Various things happen during the procedure inside of the furnace:
- Through the exposure to heat, the water content of the beans is lowered from 10-13% down to 1-2,5%. This causes the coffee beans to lose weight.
- The skin of the beans bursts due to the increase of volume of up to 70% and the aromatic coffee oils leak out.
- During the so-called Maillard reaction, the beans receive their brown color. The reaction produces up to one thousand different aroma substances from just a couple of starting materials. These cause the coffees very unique aroma.
- The glucose, the fruit sugar contained inside of the beans is caramelized by the heat, determining the sweetness of the coffee depending on the amount of sugar and the stage of caramelization.
- Caffeine is heat resistant and fully remains inside of the beans. Pesticides on the other hand fully disappear during the process of roasting. Therefor, even non organic coffee can be consumed without health risks.
- The heat reduces and converts the coffees acidity. Especially slow and gentle roasting reduces the acidity considerably. Slow-roasted coffee is usually very gentle to the stomach and well-digestible.
Generally, there is two major methods of roasting, the traditional drum roasting method and the hot air method. Here you can read more about the differences between them.
The Difference Is In The Mix
„Blend“ is a mix of different varieties of coffee beans. Mainly for espresso coffee, the most diverse coffees from all over the world are blended together to combine their individual benefits to a harmonic and superior finished product. It is important to always roast the different varieties of coffee separately. Every batch of raw coffee beans comes with its very own set of qualities and characteristics. Different water content, bean size, sugar content and acidity require individual setting for the roasting process.
Even though, arabica coffees are often considered the higher quality coffee, robusta beans feature some properties, arabica cannot convince with. Robusta beans often feature a thick, brown cream and a superior, full body. A common blend is 75% of arabica and 25% of robusta beans for an espresso blend, probably convincing even robusta-sceptic coffee lovers. But as always: You never know until you give it a go!
In a relatively usual mixing ratio of 80% Arabica to 20% Robusta, such as the Salimbene Superbar, is a balanced espresso blend, which will certainly also taste good to Robusta doubters.
The Perfect Coffee: The Roasting Processes
Unthinkable quantities of coffee are consumed all over the world. Not only the cultivation of the coffee plants but also the transport and the roasting have changed over time. Until today, the roasting of coffee has developed into a real craft and could even be considered an art for itself.
When at first coffee was roasted in little clay pots over a little wood fire, today there is two major methods of roasting coffee, the drum roasting method and the hot air method.
The Traditional Way: Drum Roasting
The so-called drum roasting is still used in most of the smaller and more traditional roasting companies. Drum roasters are available in lots of different shaped and sizes, by now even in versions small enough for your garage. The raw coffee is poured into a circular, roaring drum. The drum is heated externally, either electrically of by burning fossile fuels like wood or oil. The rotating drum is transmitting its heat into the coffee through direct surface contact with the beans.
This gentle method develops the coffees aromas particularly well because the longer roasting duration of 15 to 20 minutes at 180 to 230 °C reduces acidity and makes the coffee more digestible. During the process, the roast master regularly takes samples through a small opening and checks the degree of roasting until the perfect stage is reached.
Not just a good eye but also a lot of experience and training is required for the roast master to determine the perfect moment to interrupt the roasting and create a well roasted and consistent batch.
Because the coffee beans contain a lot of heat after the roasting process, the beans need to be cooled off immediately so that the internal heat doesn’t advance the roasting any further. Therefor the coffee is poured from the drum directly on a large, flat sieve. Cold air is blown through the sieve, cooling the beans down while an agitator stirs them.
Industrial Hot Air Roasting
Because a lot of coffee varieties are incredibly popular today, roasting companies had to find faster, more efficient ways of roasting their coffee in big amounts. By industrially roasting coffee with hot air, the companies can save a lot of time and money.
Normally, hot air roasters are designed as continuous systems. They consist of a large, perforated drum with a spiral conveyor, just like an auger, on the inside. At up 700 °C, the coffee beans are only roasted one to five minutes before they are cooled down again with cold water. Even though this method allows for continuous roasting of incredible quantities of coffee, the quality can sometimes suffer considerably. Because of the short duration of heat exposure, there is less time for the chlorogenic acids to transform and reduce. Also, the cooling water is soaked up by the beans, falsifying the coffees weight and aroma. Therefor, really good coffee is still roasted the traditional way.
Here, at Espresso International, we really value the quality of all our products. All our coffees are gently roasted with the traditional drum roasting method.