Professional Coffee Roasting | Understanding the Three Key Factors of Roasting Profiles Through Daily Roasting Processes

Professional Coffee Knowledge Exchange

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Of the factors that shape a cup of coffee's flavor, raw beans account for 60%, roasting for 30%, and extraction for 10%. Good roasting maximizes a raw bean's unique character while minimizing defective flavors. Today, let's learn some roasting knowledge with FrontStreet Coffee:

1. The Basic Structure of Coffee Roasters

Coffee roasters on the market fall into three general types, and commercial roasters come in many makes - PROBAT, Diedrich, San Franciscan, Toper, Garanti, Has Garanti, Joper, Proater, Loris, Fuji-Royal, Bonmac, and so on. Sandouke from Shanghai, China, is also quite good.

• Direct Fire Roaster
• Semi Hot-Air Roaster
• Hot-Air Roaster

Before we start roasting, let's get to know a roaster's basic structure. We're using a Yangjia Pegasus 600-gram roaster (a semi hot-air roaster):

2. The Damper Controls Air Flow and Speed in the Roasting Chamber

This is usually done by adjusting the opening of a damper plate installed in the flue pipe ahead of the roaster's exhaust fan - or, on some roasters, by adjusting the fan speed itself.

The damper setting affects how effectively hot air heats the beans in the chamber. With sufficient heat, opening the damper slightly enhances the hot air's effect on the beans. But with insufficient heat, or a damper opened too far, the roasting chamber loses temperature. When necessary, opening the damper wider can more quickly carry away the silver skin and particles that might cause off-flavors during roasting. Damper size also affects pressure in the chamber, influencing how the beans develop.

3. Three Key Factors Before Starting a Roast

FrontStreet Coffee suggests keeping good records before roasting - bean moisture content, density, origin, processing method, plus the temperature and humidity of the roasting room - and planning your roasting curve.

Key One: Warming the Roaster

Using the roaster's standard bean drop temperature as a reference - 200°C here - you must first let the chamber temperature stabilize above 200°C. Set the damper to maximum and warm up for about 30-45 minutes. After 45 minutes, when the temperature reaches 200-210°C, warming is complete.

If the chamber reads 210°C and we want to drop beans at 200°C, we can close the damper to let the temperature fall to 200°C before charging. A rapid temperature drop isn't recommended: in a roaster's mechanism, excess heat (gas volume) only raises the surface temperature of the chamber, not the chamber's overall temperature.

Key Two: Set the Drop Temperature Based on the Raw Bean

Today's example is Papua New Guinea Paradise Bird, Typica variety - a low-density raw bean, so it doesn't suit dark roasting. It naturally has refreshing acidity and fruity aromas, so we'll choose a medium-light roast, focusing on heat adjustment after first crack. Assess the bean's basic condition first, then decide the roasting approach: this is a washed, low-density bean with 10% moisture content from the 2017 crop. Based on its current state, we set the drop temperature at 200°C.

Key Three: Heat Adjustment

Roasting is a delicate process. Heat too strong, and the outside cooks while the inside stays raw; heat too weak, and the inside overcooks. The key to roasting beans evenly inside and out is proper heat control.

Raw beans: 550g. Specific operations:

When the chamber reaches 200°C, drop the beans with the damper at 3. After 1 minute of steaming, adjust heat to 160°C, damper unchanged. When the chamber reaches 160°C, adjust heat once, reducing to 115°C. Roast until 5'35", temperature 152°C, when the bean surface turns yellow (the Maillard reaction begins), the grassy smell disappears completely, and dehydration is complete. Adjust the damper to 4 (steam is produced at this point - open the damper wider to release it).

Ugly wrinkles and dark spots appear on the bean surface, and the toast smell clearly turns to coffee aroma - the prelude to first crack. Listen carefully for the sound. At 8'40", first crack begins. Keep the small heat unchanged, damper fully open to 5 (exhausting at this stage). Adjust heat to 40°C, and drop the beans at 191.3°C (a light-medium roast).

First Crack Stage: Maximum Damper

First crack is one of the stages of roasting that demands the most care and concentration. Earlier, continuous heating turned the moisture inside the beans into steam.

As heating continues, the steam inside the beans plus the carbon dioxide from the Maillard reaction builds enormous pressure against the bean's cell structure. When the pressure finally exceeds what the bean can bear, the cell structure ruptures - steam, carbon dioxide, and other substances gush out - and that is the start of first crack. First crack produces a lot of smoke, so we open the damper to maximum at this stage!

Recording the Roasting Curve:

FrontStreet Coffee Recommendation

Roast level decides a coffee's final flavor: darker roasts taste more bitter and fuller-bodied, lighter roasts more acidic and lighter. For balance in between, medium-roasted beans are the sweet spot, and FrontStreet Coffee offers several standouts.

If you dislike both sourness and bitterness, go for FrontStreet Coffee's Brazil Fazenda Rainha (Queen Estate) - the local Yellow Bourbon variety from the world's largest coffee producer. Medium roasting brings out cream, peanut, chocolate, toasted bread, and sugarcane aromas with a quiet, gentle sweetness, and the beans work as pour-over, in a moka pot, or through an espresso machine. Want something fruitier but still medium-roasted? FrontStreet Coffee's Strawberry Candy (Caomeitang) Geisha blend is the pick: it marries a honey-processed Costa Rican component with washed Panama Geisha, and the medium roast highlights both the orange-blossom honeyed character and a rounded sweetness - lovely as cold brew, pour-over, or espresso.

And for balance in its purest form, FrontStreet Coffee's Jamaica Blue Mountain No. 1 - Typica grown under Jamaica's uniquely favored geography - is roasted medium so its acidity, bitterness, sweetness, and mellowness fuse into one elegant, captivating whole: chocolate, roasted nuts, cream, and caramel from the very first sip, a harmony no other coffee can match.