A few days ago, we reviewed an article related to fluid bed roasters; the comments for and against them have really caught our attention. After having experimented 30 years with them we would like to share some advantages and limitations of these roasters and then move on to their enormous contribution towards hybrid roasters.
The different mechanisms of heat transmission (conduction, convection, and radiation) cause different sensory results in the same coffee beans. All three of these mechanisms are crucial and letting one of them predominate usually leads to unwanted results. Using conduction as the predominant heating method tends to slow down the roasting process and offers little control of the chemical reactions occurring inside the coffee bean. The predominance of convection causes weak and often rancid flavors. Using radiation as the main heating mechanism means that the pores of the coffee bean will likely not seal properly and therefore this setup will dry out the coffee and strongly affect the crucial Maillard reaction.
Fluidized bed roasters can quickly and accurately transfer heat to the surface of the coffee bean, but the ability of the beans to absorb heat is another story, affected by density, temperature differential and air/volume of coffee ratio, among other factors.
Lack of expertise on how to dose the energy in these roasters may create coffee with a series of sensory defects like:
· unbalanced flavors
· excess of organic acids
· herbal notes
· sour taste
· burned taste
· smokiness due to the excessive application of heat
Additionally, it may also cause coffees with flavors that fade quickly over just a few days due to a low-density particle that allows for an excessive loss of volatiles and a greater exposure to the oils that can make coffee taste slightly rancid.
We have noticed that in many cases, roaster operators tend to blame their tools. In most cases, it is the lack of understanding and control over the equipment that causes issues rather than the machine itself, whose ease of operation in some models is undoubted.
Hybrid systems were created to optimize the heat transmission. These roasters allow conduction to dominate at the beginning of the roasting process, followed by a mix of radiation and convection meant to transmit heat without causing dehydration. It is best to avoid excessive loss of water and volatiles at the beginning of the roasting curve and finely control the pyrolysis reactions. At the same time, one can develop positive attributes to prevent the grains from burning and tarring due to excess smoke and heat.
The contribution of convection roasters (fluidized bed) to the latest technology is unquestionable, now we must understand the importance of transmitting heat by the different mechanisms.
We believe that roasters will tend to evolve towards hybrids in a not-so-distant future since they tend to be quieter, consume less energy, produce less air pollution, and have a lower cost of installation and operation. These roasters combine the wonder of traditional roasters, fluidized bed roasters and more ecological roasters, taking us closer to the ideal scenario of sustainable coffee.
Coffee-Tech Engineering has one of the most complete product lines when it comes to hybrid roasters. Their laboratory roasters, specifically the new FZ-94 EVO, give the operator complete control over all three heat mechanisms. Let us evolve towards a cleaner world with better coffee. The SHB Caffé team is always available for any question, whether technical (pablo.contreras@shbcaffe.com ) or commercial (rod.mendoza@shbcaffe.com ).
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pablo.contreras@shbcaffe.com) o comercial ( rod.mendoza@shbcaffe.com ).