What are the coffee roasters the difference between a semi-hot air roaster and a direct roaster

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Semi-hot air (Half Hot Air Roaster), as its name implies, is a baking method that has the advantages of both direct fire and hot air. Van Guban, a German, improved and manufactured a barrel roaster in which hot air was introduced into the baking chamber through a small hole in the drum.

In 1907, the German Perfekt roaster began to introduce this concept, using gas heating, there is an air pump, half of the hot air into the drum, half to the outer barbecue drum. Commercial baking machines have been in the mainstream since 1910. The German Probat drum roaster is the most famous. The heating drum makes the internal heat of the drum transfer directly to the raw bean, but unlike the direct fire type, the semi-hot air drum is made of thick iron plate without holes, so the flame will not directly touch the coffee beans, so it is not easy to scorch the bean table.

In addition, a ventilation equipment is added to introduce the heat from the heating drum and the hot air passing through the heat source into the baking room, so that the baking can obtain stable heat and make it heated uniformly. In addition, the ventilation equipment can also suck out the shedding silver skin, so that the coffee beans will not smell because of the silver skin. In the construction of the baking mechanism, excluding the exhaust valve to regulate the hot air exhaust, the baking operation becomes relatively simple, and a good baking reproducibility is obtained, so it has become the standard way of the modern roaster. However, compared with the direct fire type, the coffee baked by the semi-hot air roaster does not have a prominent personality.

Direct Fire Roaster, literally, is to heat coffee beans directly with a flame. The biggest feature is that the drum has a small hole, and the fire can burn directly to the bean watch. Although the coffee beans can be heated evenly by stirring the drum, the heat is difficult to control, so it is easy to scorch the surface of the beans, while the stamens are not fully ripe when the beans are cut open. The direct fire type adjusts the heat through the exhaust valve, and its operation is also cumbersome, so the reproducibility of the baking result is poor. In addition to the general flame (including gas furnace fire and charcoal fire), the "fire" of direct fire now includes infrared and electric heating pipes.