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

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Among the factors that affect the flavor of a cup of coffee, raw beans account for 60%, roasting accounts for 30%, and extraction accounts for 10%. Good roasting can maximize the unique characteristics of raw beans while minimizing the appearance of defective flavors. Today, let's learn about roasting knowledge at FrontStreet Coffee:

1. Basic Structure of Coffee Roasters

Coffee roasters on the market are generally divided into three types, and commercial coffee bean roasters come in various varieties. Such as PROBAT, Diedrich, San Franciscan, Toper, Garanti, Has Garanti, Joper, Proater, Loris, Fuji-Royal, and Bonmac, etc. Sandouke from Shanghai, China is also quite good.

• Direct Fire Roaster
• Half Hot Air Roaster
• Hot Air Roaster

Before starting to roast, let's get to know the basic structure of a roaster. We're using a Yangjia Pegasus 600-gram roaster (Half Hot Air Roaster):

2. The Damper's Purpose is to Control Air Flow and Speed in the Roasting Chamber

Generally, this is achieved by adjusting the opening of a damper plate installed at a certain position in the flue pipe before the roaster's exhaust fan, or in some roasters, by adjusting the speed of the exhaust fan.

The size of the damper affects the heating effect of hot air on raw coffee beans in the roasting chamber. With sufficient heat, slightly increasing the damper can enhance the hot air's effect on the raw coffee beans. However, insufficient heat or an excessively large damper can cause temperature loss in the roasting chamber. When necessary, opening the damper wider can more quickly remove the silver skin and particles that might cause off-flavors during coffee roasting. Damper size also affects the pressure in the roasting chamber, influencing the development of coffee beans.

3. Three Key Factors Before Starting Coffee Roasting

FrontStreet Coffee suggests keeping good data records before roasting: coffee bean moisture content, density, origin, processing method, roasting environment temperature and humidity in the roasting room, etc., and planning your roasting curve.

Key One: Warming the Roaster

Referencing the basic bean drop temperature for the roaster used, with 200°C as the standard, you must first let the roasting chamber temperature stabilize above 200°C. Set the damper to maximum, with a warming time of about 30-45 minutes. After 45 minutes, when the temperature reaches between 200-210°C, the warming is complete.

If the roasting chamber temperature is at 210°C and we need to drop beans at 200°C, we can close the damper to let the temperature fall to 200°C, then proceed to the next step of dropping beans. Rapid temperature increase is not recommended because in the roaster's mechanism, excessive heat (gas volume) only increases the surface temperature of the roasting chamber, not the entire chamber's temperature.

Key Two: Determine Bean Drop Temperature Based on Raw Bean Properties

Today we're referencing Papua New Guinea Paradise Bird, Typica variety, which is a low-density raw bean, so it's not suitable for dark roasting. It naturally has refreshing acidity and fruity aromas, so we'll choose a medium-light roast, focusing on heat adjustment after the first crack. First, assess the raw bean's basic conditions, then decide the roasting method. It's a washed processed, low-density bean with 10% moisture content from 2017. Based on the current raw bean state, we set the drop temperature to 200°C.

Key Three: Heat Adjustment

The roasting process is tricky. If the heat is too strong, the outside will be cooked while the inside remains raw. If the heat is too weak, the inside will be overcooked. The key to achieving uniform roasting inside and out of coffee beans is proper heat control.

Raw beans: 550g. Specific operations:

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

At the 9th minute, ugly wrinkles and dark spots appear on the bean surface, toast smell明显 turns to coffee aroma, which can be defined as the prelude to first crack. At this time, listen carefully for the sound of first crack. At 8'40", first crack begins. Keep small heat unchanged, damper fully open to 5 (exhaust at this time). Adjust heat to 40°C, drop beans at 191.3°C (属于浅中烘焙).

First Crack Stage: Maximum Damper

The first crack stage is one of the stages in the coffee roasting process that requires the most care and concentration. Previously, due to continuous heating of coffee beans, the moisture inside the beans became steam.

Due to continued heating in the later stage, the steam inside the beans and carbon dioxide from the Maillard reaction create great pressure on the bean's cell structure. Finally, when the pressure becomes too great and the beans cannot bear it, the coffee bean cell structure ruptures, and steam, carbon dioxide, and other substances gush out from inside the beans, indicating the beginning of first crack. Therefore, first crack produces a lot of smoke, so we open the damper to maximum at this stage!

Recording the Roasting Curve:

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473