What is the Ideal Roast Level for Blue Mountain Coffee: Blue Mountain No.1 Coffee Bean Roasting Curve

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FrontStreet Coffee Jamaican Blue Mountain Coffee Roasting Curve

Bean Entry Temperature: 170°C

Roasting is the source of coffee flavor. The process of applying fire to raw beans is called roasting. Raw beans cannot be consumed without roasting. After roasting, coffee beans determine 80% of the coffee's taste. The roasting process is tricky - if the fire is too strong, the exterior will be cooked while the interior remains raw; if the fire is too weak, the interior will be overcooked. The key to achieving consistent roasting inside and out is to control the heat properly.

Heat Level

The heat level directly affects the roast degree of coffee beans, their flavor, and the desired roasting time. Greater heat produces more flavors, but not all flavors may be desirable. Sufficient heat allows coffee beans to release more flavor compounds, but it also highlights undesirable flavors inherent in the beans.

Temperature Recovery Point

When beans enter the roasting drum, they immediately absorb heat, causing the drum temperature to drop sharply. Then, at a certain point in time, the temperature begins to rise again. This equilibrium point is the temperature recovery point.

Yellowing Point

Raw beans enter the heat absorption stage. To transfer heat to the interior of the beans, water conductivity is utilized. If the beans have low moisture content, they will reach the yellowing point more quickly. Conversely, if the beans have high moisture content, they will take longer to reach the yellowing point. Water evaporates and converts to steam, causing the internal steam pressure and temperature of the beans to rise. At this point, the beans begin to expand in structure, breaking down chlorophyll and entering the yellowing point.

We also sampled some beans during the roasting process to observe how these changes occur.

Throughout the entire roasting process, we need to coordinate the use of the air damper to adjust the coffee beans' flavor to their optimal state while ensuring the cleanliness of the coffee beans.

Proper caramelization gives coffee higher complexity and layers, a fuller body, and brings caramel aromas, chocolate, and roasted flavors to the coffee. Pyrolysis reactions cause substances that contribute plant-based flavors to coffee to decompose.

First Crack

First crack refers to the obvious and strong sounds emitted by coffee beans during roasting, somewhat similar to the sound of making popcorn or burning firewood. When coffee beans absorb heat until the pressure generated by water evaporation inside the beans exceeds the strength of the coffee beans themselves, the cell walls of the coffee beans will crack due to being unable to withstand the pressure from the expanding core. At this moment, the coffee beans emit first crack sounds, releasing thermal and acoustic energy.

This is how "first crack" occurs. Different flavor compounds are released (aromatic substances such as floral and fruit notes), and browning occurs (which is why coffee beans are brown in color). This is also when coffee beans undergo significant development - even being discharged one second earlier or later can result in significant flavor differences.

Temperature Rise

The temperature difference between two time points. For example, between the 2nd and 3rd minute in the diagram, there will be a temperature difference. By subtracting the former temperature (108.8°C) from the latter (122.4°C), we obtain a value (13.6°C).

Taking the roasting of FrontStreet Coffee Jamaican Blue Mountain Coffee as an example, it's important to understand the characteristics of these beans. FrontStreet Coffee Blue Mountain Coffee consists of NO.1 beans sized 17 screen or larger, with a defect rate below 3% and moisture content around 13%. The beans have medium density and are suitable for roasting using a steady, gradual approach.

In the process of designing roasting curves, my personal experience is that attention should be paid to the fact that FrontStreet Coffee Blue Mountain roasting curves are suitable for lower bean drop temperatures. Due to the beans' lower density, the temperature rise after first crack should not be too high - a temperature rise below 6°C would be better, extending the development time.

First, when the drum temperature reaches 170°C, add the beans with the air damper set to 3. After 1 minute, adjust the heat to 140°C, keeping the air damper unchanged. Roast until 5'10", when the temperature reaches 153°C, the bean surface turns yellow, grassy aromas completely disappear, and dehydration is complete. Adjust the heat to 115°C and change the air damper to 4.

At the 8'00" minute, ugly wrinkles and black spots appear on the bean surface, and the bread aroma clearly transitions to coffee aroma. This can be defined as the prelude to first crack. At this time, listen carefully for the sound of first crack. At 8'12", first crack begins. Reduce the heat to 90°C and open the air damper fully (adjusting the heat requires extreme care - it should not be so low that crackling sounds disappear). Drop the beans at 201.3°C.

Important Notice :

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