The process of roasting green coffee. Learn how our brands roast their Premium Specialty Coffees.

The process of roasting green coffee

 

The secret of roasting coffee lies in knowing how to calibrate the roasting curve. That is to say, in maintaining the exact temperature, during the correct time, in each stage of the process.

 

Master roasters calibrate the roasting curves depending on the particular characteristics of the green beans. In this way they are able to obtain a roasted coffee in which certain attributes of flavor and aroma stand out.

 

Coffee Beans and Birds sells coffees from different origins in Colombia, from Antioquia, passing through Risaralda, Caldas, Huila to coffees from Nariño in the south of the country.

 

Each coffee farm uses a different roaster, either on their own farm or by renting the services of an authorized roaster in their region. However, depending on its origin, variety and quality each brand has different roasting curves. Every farm’s master roaster decides what type of roasting is be done and perform it to get roasted beans to perfection.

 

Here we explain the roasting process of two of our favorite brands, The Pristino and Del Poeta coffees.

 

Step 1. Roasting the green coffee: 

In this step we define the roasting grade. Our coffee growers define the level of roasting according to the variety and the type of preparation for which the coffee will be used. In the case of The Pristino coffee we have different roastings: high, medium-high or medium roastings, while for Del Poeta coffees we use low and medium roastings due to the varieties they handle.

 

• High roast: This is used most of the time for strong coffees such as espresso or macchiato. The high roast results in a bitter beverage with a flat taste, in which no special attributes of flavor and aroma can be differentiated.

• Medium roast: This roast is the most commonly used in high quality and specialty coffees, that is to say, most of the coffees Coffee Bean and Birds works with. This type of roasting allows to highlight all the attributes of acidity, flavor, body, sweetness and aroma of a great cup of coffee.

• Low roasting: It is used for very particular varieties of coffees such as the Geisha variety, as already mentioned by Café del Poeta, which exhibits a very subtle flavour and aroma that disappears as the degree of roasting increases.

 

 

 

Good to know that the degree of roasting is defined according to the change in color of the beans as the roasting time passes, and that the 45% percent of the final premium added value of our specialty coffees comes from the process of roasting.

 

Since we sell the Most Premium coffees in Colombia, our coffee roasters are true masters. Experts who have a whole ritual for this specialized task.

 

Step 2. Define the roasting curve:

 

Our roasters know how to calibrate the exact roasting point "by eye" and "by ear", observing the color changes in the almonds as the roasting time progresses.

 

The roasting temperature in the industrial machines such as the PRISMA, in which the Poeta's coffees are roasted, begins with the oven preheated to 200°C (120°F). This Prisma drum roaster is a specialized industrial equipment for the roasting of special coffees with high technical requirements in its curves and developments such as ours. 

 

The Pristino coffee carries out its selection process in XELTRON roller machines, which have an electronic optical analyzer that analyzes the bean at 360° and is the preferred model for Micro lots and Specialty coffees with a selection volume of up to 200 Kg/h. 

 

Then, coffee passes on to the roasting process through an INGESEC fluidized bed machine which allows experts to control manually or completely automatically batch by batch, and whose rotation allows a steady transfer of heat by conduction and convection in order  to the complete uniformity of the roast at every bean.

 

In general, all the roasting processes carried out by each of the Coffee Bean and Birds’ brands are performed in one of the two types of roasting machines, either drum or fluidized beds. 

 

The difference between drum and fluidized bed roasting is simple. In a drum roaster, the metal drum is heated, which then transfers the heat to the beans. Whereas with a fluidized bed roaster, air is first heated and then blown through the roaster bed, eliminating the need for a heated drum.

 

Drum roasters allow control of the amount of air entering and leaving the roaster in order to maintain a certain level of humidity for Specialty coffees. However, if the coffee is roasted above a certain level of humidity established by the brand, it will be "dry" and will lose its complexity and its more subtle flavors.

 

Brands such as The Pristino coffee that use the INGESEC fluidized bed   machine only use air to heat the coffee instead of the residual heat from the drum, which makes the loss of moisture at the beginning of the roast more of a concern as the beans can end up having a flat flavor once roasted.

 

Likewise, no matter the type of machine, the general roasting process that our coffees undergo follows the following scheme:

 

After loading the coffee, the temperature drops by half and then gradually rises again at a rate of 10°C per minute. If it rises faster, the coffee beans are roasted externally but remain raw and hollow on the inside.

 

 

The first crack

About 12 minutes into the process, when the temperature has risen again to 193°C, the first "crack" occurs.

 

This is a cracking sound like that of a popcorn popping. This sound occurs because the coffee bean expands, increases in volume and explodes internally, releasing gases and water vapor to the outside.

 

It indicates to our expert roasters that it is almost at the end of the process and the time remaining depending on the degree of roasting that has been chosen.

 

If it is a low roast, this first crack indicates that the coffee is almost at its roasting point.

 

If it is a medium roast, it will take approximately 2 to 3 minutes after hearing the first crack and the temperature will reach 200°C.

 

In this case the total roasting time is between 14 and 16 minutes.

 

 

The second crack

This is a much more subtle crack than the first one and indicates that the roasting process should be stopped.

 

From this point on, the sugars begin to caramelize and carbonize, the fatty acids rise to the surface and the quality of the coffee begins to deteriorate.

 

In a high roast, the temperature rises to 218°C and the coffee is dropped into the cooler just before or after hearing the second crack.

 

 

Step 3. Cooling the coffee:

 

When the desired degree of roasting is reached, the temperature of the beans should drop in less than 30 seconds to 175°C and in 3 minutes should reach room temperature. In this way, the roasting process is slowed down and the fatty acids of the almonds are prevented from coming to the surface.

 

For both The Pristino and Del Poeta coffees, the cooling system operates independently, ensuring continuous roasting rates of up to 125 kilograms/hour.