Hot air
The hot air roaster uses a blower to inhale air, and then lets the air pass through a heating coil to increase its temperature, and uses hot air as a heating source to roast coffee beans. The hot air can not only provide the temperature required for roasting but also use the airflow to stir the coffee beans with strength and kill two birds with one stone. This type of coffee roaster is popular among home roasters, as it is easy to use and clean. You can find many coffee roasters for sale online that use the hot air method.
Advantages: high thermal efficiency, fast heating, relatively uniform heating of green beans, easy to control.
Disadvantages: Because of the high heating efficiency, it is easy to cause the temperature to rise too fast, causing the beans to be “cooked”, and the caramelization reaction is not sufficient if the temperature is too high.
Taste characteristics: The acidity is obvious, and the taste is relatively clean and simple, but the taste is not rich enough and lacks depth, and deep roasting is prone to produce a pungent taste.
Direct fire
The direct fire method uses a flame to directly heat the coffee beans. So far, the “fire” of direct fire includes infrared rays and electric heating tubes in addition to general flames (including gas stove fires and charcoal fires). This type of coffee roaster is more suitable for professional roasters, as it requires more skill and experience to control the fire and avoid burning the beans. Some of the best home coffee roasters also use the direct fire method, but they are more expensive and complex than the hot air ones.
Advantages: The roasting time is longer so that the caramelization reaction is more sufficient and the taste is richer.
Disadvantages: It is easy to cause uneven roasting, and if the fire control is not good, it is easy to burn the coffee beans and form a burnt bitter taste.
Taste characteristics: The body is full, the aroma is strong, and the sweetness is prominent, but the acidity is low and the bitterness is high.
Semi-direct fire semi-hot air
The roasting method that combines the advantages of direct fire and hot air is currently the mainstream of commercial baking machines. Semi-direct fire roasting is actually similar to direct fire roasting, but because there are no holes in the outer wall of the roasting container, the flame will not directly touch the coffee beans; The hot air is introduced into the roasting chamber to improve the roasting efficiency. Another function of this ventilation device is to suck out the peeled silver skin (the film attached to the outer layer of coffee seeds) to prevent the silver skin from burning due to the high temperature in the roasting chamber, thereby affecting the taste of coffee beans. This type of coffee roaster is widely used by coffee shops and roasting factories, as it can produce consistent and high-quality roasts. Some of the most famous brands of this type of coffee roaster are probat coffee roaster, electric coffee roaster, and commercial coffee roasting machine.
The semi-direct fire and semi-hot air machines have both the advantages and disadvantages of direct fire and hot air, but the heating method is changed according to the adjustment of hot air and boiler speed. The bigger the hot air is, the faster the speed is, the closer to the hot air type; otherwise, the closer to the direct fire type.