COMPARE THE DIFFERENCES BETWEEN HOT AIR, SEMI-HOT AIR AND HOT DRUM

Hot air roasting technology, Semi hot air, hot drum, these terms are very familiar if you are working in the field of coffee roasting and grinding, or you are learning and a little interested in coffee roasting machines. But not everyone knows and understands these roasting technologies better. Today, Mars would like to share more deeply about the differences as well as the advantages and disadvantages of these roasting technologies.

1. Hot air roasting technology: means heating the air in another location, also known as the combustion chamber, and then the hot air will be blown into the roasting drum through the coffee beans and evenly distributed in a roasting drum to ripen the coffee.

What are the advantages of hot air roasting technology?

• With Hot Air roasting technology, coffee beans will be guaranteed to be heated evenly and cooked from the inside to the outside, thus overcoming the problem of roasted coffee being burned on the edges and cooked unevenly.
• In addition, Hot Air roasting technology overcomes the problem of coffee roasting being smoky and tasting acrid and burnt due to the silkverskins coming off during the coffee roasting process. If not vacuumed and taken outside, when coffee beans exposed at high temperatures, the silverskin will burn very easily, forming burning dust particles that stick to the coffee beans and the drum wall.
• Roasting coffee machines using hot air technology require less cleaning of the roasting coffee drum than machines using the other two technologies. That’s because when hot air is circulated from one end to the other, along with the suction force of the fan, it will suck the silverskin and dust out, ensuring the roasting drum is always clean and not burned black on the drum walls.
• And a superior feature that must be mentioned is the economic efficiency of shortening roasting time and saving fuel – saving gas (Mars will continue to analyze in the next article “why roasting technology is hot air saves more fuel”).

What are the disadvantages of coffee roasting machines using Hot air technology?

• The biggest disadvantage when using a coffee roaster with hot air technology is high production costs. Because of the complexity of the mechanical structure as well as the combustion chamber system, the product cost of coffee roasting machines using hot air technology will be higher than coffee roasting machines using other technologies.

(Photo illustrates the working mechanism of the hot air line)

2. Direct combustion roasting technology (hot drum): Heat is taken directly from the burner in direct contact with the outer wall of the roasting drum. Coffee beans are heated by direct contact with the walls of the roasting drum.

Advantages of direct combustion roasting technology (hot drum): The design and structure of the coffee roaster is simple and easy to manufacture, so production costs are low.

Disadvantages of direct combustion roasting technology:

• During the coffee roasting process, the friction and contact between coffee beans on the walls of the roasting drum is not uniform, some beans have a lot of contact, some have little contact, the beans coffee are already cooked but continue to be heated, leading to uneven ripening of coffee beans and scorched edges.
• Drinking coffee tastes acrid, burnt and has a smoky smell due to the burning of the silverskin during the roasting process but not being cleaned, leading to a reduction in coffee quality.
• Not stopping there, when the silverskin burns, it will stick to the roasting drum, making the drum roasting cleaning process very time-consuming and laborious. You must regularly clean the roasting drum to remove the black burnt layer stuck inside the drum. If you do not clean it and continue to use it the next time you roast it, this burnt layer will stick to the coffee and will reduce the quality of the roasted beans, which is why people often see roasters that have been used for a while. That’s why roasted coffee often gets smoky. In particular, these flammable ingredients negatively affect consumers’ health.
• Consumes more fuel than high-capacity machines using hot air roasting technology.

3. Semi-hot air roasting technology: means 50% of the hot air is put into the drum and the remaining 50% of the heat is taken directly from the bottom of the roasting drum. Regarding the advantages and disadvantages of semi hot air roasting technology, it neutralizes and overcomes some of the advantages and disadvantages of the two roasting technologies mentioned above.

Semi-hot air roasting technology partly solves the problem of uneven ripening, burnt skin, smoke… caused by direct combustion roasting technology (hot drum) and reduces production costs compared to hot air roasting technology. However, semi-hot air roasting technology is not the best solution for roasting coffee to achieve the best quality.

Conclusion: Through the above analysis, we see that it is not obvious that Hot air roasting technology has become the most advanced, modern and optimal roasting technology today. That’s why hot air roasting technology is highly appreciated by famous roasting companies and international experts.

Many customers are still confused between the two technologies of roasting hot air and semi hot air, possibly because the manufacturer’s advice is not clear or maybe customers do not really understand the operating mechanism between these technologies.

If you want to learn about the structure and operating mechanism of roasting technologies, please visit the Mars Roaster’s factory to have a practical and in-depth experience about the production process of each type.