Commercial coffee roasters mainly include three types: direct fire type, semi-hot air type and hot air type.
Direct fire type: The boiler surface has a perforated design, and the fire is directly conveyed into the furnace chamber, which requires high technical skills from bakers. The advantage is that the preheating time is short, which can better bring out the flavor of estate beans and is suitable for single-blend beans or single-type bean coffee. The drawback is that it is easily affected by the external environment, such as indoor and outdoor temperatures, air circulation, etc.
Semi-hot air type: It combines the features of direct fire and hot air, makes up for the shortcomings of direct fire, enhances safety, and can easily present the aroma and flavor of coffee. The internal temperature of the boiler is easy to adjust, the firepower is stable, and it is suitable for blending coffee and roasting.
Hot air type: Air is drawn in by a blower, heated through a heating coil, and then hot air is used as the heating source to roast coffee beans. The advantages are high thermal efficiency, fast heating, uniform heating of green beans that is easy to control, suitable for light and medium roasting, and highlighting clean acidity. The drawback is that it can heat up too quickly, causing the beans to be “undercooked”. Moreover, if the temperature is too high, the caramelization reaction will not be sufficient, resulting in insufficient flavor richness and depth. Deep roasting is prone to produce pungent flavors.