Flavor Differences Between Coffee Bean Roasting Levels | Blue Mountain No.1 Coffee Bean Roasting Temperature

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Many of coffee's flavors are expressed through roasting. As the roasting level varies, the flavors also manifest differently. In this article, FrontStreet Coffee will share the different flavor profiles and mouthfeels of coffee beans at various roasting levels.

The Coffee Bean Roasting Process

Coffee bean roasting generally goes through the following stages:

Loading: Before loading the beans, the roaster is preheated to maintain a stable drum temperature. Generally, the beans can be loaded when the preheating temperature reaches 180-200°C.

Dehydration Stage: After loading, the beans begin to absorb heat, and the drum temperature drops to around 100°C. About 1-2 minutes after loading, when the drum temperature reaches its lowest point and begins to rise again, this marks the temperature recovery point.

At around 5 minutes, the beans turn yellow, and their original grassy aroma transforms into a toasted bread fragrance. This is the yellowing point. The heat absorbed by the beans penetrates to the interior, and the fiber structure of the beans begins to change and expand. At this stage, the temperature is steadily and continuously rising.

First Crack: This refers to the "popping" sound produced when the pressure from water evaporation inside the beans breaks through the cell walls during continuous heat absorption. At this point, the coffee beans are in an exothermic state. Generally, 1-2 popping sounds mark the beginning of the first crack. This is followed by intense "pitter-patter" sounds, indicating the dense phase of the first crack. When the popping sounds become sporadic and finally end, this marks the conclusion of the first crack. The entire first crack process typically occurs between 9-12 minutes, and the duration of first crack development determines the coffee's flavor changes.

Second Crack: After the first crack ends, the beans return from an exothermic to an endothermic state. When the coffee beans absorb a certain amount of heat, the lignocellulosic fibers of the cell walls break, producing "popping" sounds. The oils inside the beans also flow to the surface as the fibers break, making the bean surface appear shiny and oily. The second crack sounds are slightly weaker than those of the first crack.

Cooling: Beans can be removed from the roaster at any point from the first crack to the second crack, though this will result in different roasting levels. After roasting, the beans must be cooled immediately to rapidly stop the high-temperature pyrolysis process and lock in the flavors. Otherwise, if the high temperature inside the beans continues to act, it will burn the aromatic substances and give the coffee a smoky, burnt taste. The discharge temperature is generally above 180°C.

How to Distinguish Roasting Levels

As mentioned above, coffee beans can be discharged at any point from the first crack to the second crack, and different timing nodes will result in different roasting levels. FrontStreet Coffee's coffee bean roasting is divided into light roast, medium roast, and medium-dark roast.

Using sun-dried Yirgacheffe as an example, FrontStreet Coffee conducted comparative tests with light roast, medium roast, and medium-dark roast.

Light Roast: Yellowing point at 5'00", first crack begins at 8'30", temperature 185.8°C, developed for 1'30" after first crack before discharge, discharge temperature 196.3°C.

Medium Roast: Yellowing point at 5'00", first crack begins at 8'32", temperature 186.9°C, developed for 2'30" after first crack before discharge, discharge temperature 197°C.

Medium-Dark Roast: Yellowing point at 5'20", first crack begins at 8'42", temperature 185.4°C, developed for 3'30" after first crack before discharge, discharge temperature 198°C.

Cupping the Three Different Roast Levels

[Light Roast] Wet aroma has notes of berries, cream, and citrus. When slurped, flavors of blueberry, citrus, berries, tropical fruits, and cream are present.

[Medium Roast] Wet aroma shows spice, berries, and fermentation notes. When slurped, flavors include peach, plum, lemon, cream, almond, and floral notes.

[Medium-Dark Roast] Wet aroma has spice, smoky, and cocoa notes. When slurped, flavors include nuts, dark chocolate, cream, and herbal notes.

Therefore, lightly roasted coffee has more prominent acidic fruit flavors. As the roasting level increases, the acidity gradually diminishes while sweetness becomes more apparent. At the medium roast stage, flavors of dark fruits, chocolate, and brown sugar emerge. At dark roast levels, caramelization reaction flavors become very obvious, presenting notes of nuts, cocoa, and cream.

So is there a scientific method to define roast degree? The answer is yes - by using color values to determine the roasting level:

Light Roast:

Agtron Color Value #95: Light Roast
Discharge Time: When first crack density is about to end

Agtron Color Value #85: Cinnamon Roast
Discharge Time: Around the end of first crack

Medium Roast:

Agtron Color Value #75: Medium Roast
Discharge Time: After first crack ends

Agtron Color Value #65: High Roast
Discharge Time: During the quiet period between first and second crack

Medium-Dark Roast:

Agtron Color Value #55: City Roast
Discharge Time: At the beginning of second crack

Agtron Color Value #45: Full City Roast
Discharge Time: Before second crack density

Dark Roast:

Agtron Color Value #35: French Roast
Discharge Time: During second crack density

Agtron Color Value #25: Italian Roast
Discharge Time: When oils begin to seep to the bean surface

FrontStreet Coffee's Roast Level Representatives

So what corresponding roast level representatives does FrontStreet Coffee have?

Light Roast: Represented by various African beans and fresh acidic American beans, such as coffee from Ethiopia, Kenya, Panama, and other countries, generally expressing lively fruit and floral notes.

Medium Roast: Mainly includes Brazilian coffee beans, Jamaican Blue Mountain coffee beans, Papua New Guinea's Bird of Paradise coffee beans, and Hawaiian Kona coffee beans. These are characterized by excellent balance.

Medium-Dark Roast: Mainly includes Indonesia's Mandheling coffee series, such as PWN Golden Mandheling coffee, Tiger Mandheling coffee, and Aged Mandheling coffee. These are characterized by extremely rich body, with notes of nuts, cocoa, and herbal tones.

For more specialty coffee beans, please add FrontStreet Coffee's private WeChat account: kaixinguoguo0925

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473