LEARN THE PRINCIPLE OF HEAT CONSUMPTION AND SOME FACTORS RELATED TO ROFING COFFEE

  1. Heat conduction principle
  • Heat tends to flow from hot to cold. On the same material, a material with a tighter molecular structure (harder) will transfer heat and conduct heat better. An inappropriate amount of heat applied to the roast can lead to a failure of the roast.
  • On Mars Roaster models, models 6kg or more are applied convection heat transfer method.

» Heat energy is transferred by 100% hot air (Hot Air technology)

» This convection heat transfer method is a special way of  conduction, minimizing the instantaneous heat intensity on 1 point of the coffee bean.

» The difference in temperater between the hot air and

» The difference in temperater between the hot air and the coffee beans is the instensity of the heat acting on the beans at the moment.

  1. Find out when to put coffee bean in the roasting drum (charge point).

» The charge point is the time when the coffee bean is put into the roasting drum, starting the roasting process.

» The main purpose of the charge point is to create a large heat intensity that strongly affects the coffee beans during the drying process, the main purpose is to make the evaporation of water at this stage faster, shorten the roasting time and ensure The roast is not faulty.

  • The inlet temperature (charge) along with the gas level in the roasting batch is considered the most important factor in the roasting process.
  • The inlet temperature and gas supply threshold in the roasting batch are determined after synthesizing the inputs from the kernel: species, preliminary processing method, season, moisture content of green coffee beans, etc.
  1. Factors related to coffee roasting:

3.1Species:

» Input temperature (charge): Arabica kernels have a harder grain structure than Robusta and Excelsa beans, so when roasting Arabica is allowed to charge higher than Robusta and Excelsa.

» Gas supply threshold in batch (heat supply): Because Arabica beans have high sugar content and better heat transfer than Robusta and Excelsa beans, Arabica’s gas supply threshold is lower than that of Robusta and Excelsa.

» Elevation of planting area: With the same species, seeds in higher growing areas have a harder grain structure, so the charge temperature is higher and the gas supply threshold is lower.

3.2.Processing method:

» Input temperature: The same type of beans, kernels are processed by dry processing method (Natural) and honey processing method (Honey) charge temperature is lower than wet processing method because the silver skin is often sticky. close to the kernel, and the amount of sugar left in the kernel is higher, if the heat input is high, it will easily burn the outer silver sikin layer and quickly destroy the sugar, causing a burn on the surface of the grain that cannot absorb heat inside, easily produce the phenomenon of burning outside, the inside is not ripe.

» Gas level threshold: For the same type of nut, processed by honey method has the highest percentage of sugar, processed by wet method, has the highest percentage of acid. As a result, honey-processed seeds are given a lower initial gas supply threshold than natural and fully washed, to avoid sugar burning of the nuclear surface compared to the conventional methods with the rest of the processing methods..

3.3.Season:

» past crop): After being stored for a long time, the acid is reduced (making the sweet taste higher), the grain structure is softer and porous because the seeds have self-respiration and heat exchange process => lower charge point.

» Current crop: The cell structure is stable with the surrounding environment over time, so the charge point is higher than the past crop.

» New crop: Just finished the post-harvest processing, there is no “rest” time to stabilize the cell structure (usually prone to grassy = weeds), so the charge is lower than current crop.

3.4.Moisture within beans: Ideal equilibrium moisture (12%), at this moisture contains no free water, only bound water. The higher the moisture, the lower the charge point because the more water content in the beans, the easier it is to collect water to one point, leading to the first error and more serious, starch gelatinization leading to the failure to develop coffee beans in the future. roasting process, on the contrary, the gas supply threshold is larger to provide enough heat during roasting.