In order to carry out their functions correctly, modern roasters need to be able to transmit energy (heat) through the three basic mechanisms: conduction, convection and radiation, with precision, but additionally there are other characteristics that are of great importance to be able to adequately reproduce roasting profiles or curves coffee, perhaps the most important of these are the drivers.

Most roasters have energy management systems through electromagnetic valves that open and close when reaching certain temperatures programmed by a controller and adjusted by gas regulators, or electric heaters that turn on or off when reaching the temperature programmed in the controller; However, none of these factors takes into account the temperature differential caused by the surrounding environment, nor by the temperature of the coffee beans when entering the roasting chamber; That is, it is not the same to roast coffee in the morning as the temperature is regularly cooler and the beans are colder, than to do it in the afternoon in a warmer environment, since the inlet air to the machines will need more or less BTUs * as the case may be in order to accurately follow the proposed profile.

Additionally, in negative pressure systems (those that suck air, instead of injecting it) every time a coffee sample is taken in the roasting process, cold air is brought into the roasting chamber, altering the programmed profile. substantively.

The most advanced controllers, on the other hand, open and close gas valves depending on whether the grain temperature is above or below the programmed temperature, this is done several times per minute, this type of controller automatically compensates for variations environment, but not that of the grain inlet temperature differential, which, although it registers it, cannot adequately compensate for the grain being a biochemical reaction system; In the case of cylinder roasters, this system is accompanied by the opening and closing of air inlets to be able to react more quickly to the detected deviation; however, it also alters the type and speed of heat transmission.

To solve this problem, it would be desirable to adapt a first adjustment valve or electrical resistance with variable heating to adjust the temperature of the air inlet flow to the combustion chamber to a constant temperature, before passing through the valves or resistors that control in based on temperature toast profile. In this way, the effect of the change in ambient temperature in the roasting process can be compensated, without altering other variables such as air speed or intensity of the flame during this operation, but it also requires a prior conditioning stage of the beans. green coffee, prior to roasting without causing dehydration to ensure that they enter the roasting chamber at the same temperature, avoiding the typical damage from thermal shock when the bean is very cold.

* British thermal Unit; defined as the amount of heat needed to raise 1ºF a pound of distilled water

It is also desirable to design a type of sampling that allows roasted coffee to exit without allowing cold air to enter the roasting chamber, avoiding impact on the registers, giving greater control of the roasting process, they are easy to prepare, but not there are many brands that handle it.

The lack of solving these problems applies to all roasters that have between two or more valves adjustable to the roasting profile, regardless of whether they are air or cylinder and although a previously developed roasting curve can be perfectly followed, the impact reactions and taste are not completely standardized due to these factors.

Finally, there is a common problem with the design of many of the roasters since they must heat and cool efficiently and quickly, otherwise it is impossible to achieve adequate control of the roasting process when it is required to continuously operate several roasting profiles.

When the mass of the roaster is very large, time is required to heat or cool it, especially if the convection transmission mechanisms are limited, this causes a decrease in the productivity of the machine and increases the operating costs; However, it is not only a matter of supplying more air, metals that heat up and cool down quickly tend to fatigue soon, especially if they are of low quality, which increases the cost of the equipment considerably.

Undoubtedly, these are factors to be taken into account when choosing a particular brand of roasters and variables to consider during the process of designing and monitoring roasting profiles.