With Rotating Drum This formula is based on an operating principle:
- Conductivity with convection
- Roasting by direct contact of the walls of the drum, heated by the flame with the flow of hot air.
- The roasting time varies between 8 and 17 minutes.
Fluid This formula is based on an operating principle:
- Switching heat
- Hot air flow, allowing more identical firing temperature control and precise synchronization.
- Roasting time varies between 8 and 17 minutes.
The heat used in roasting causes the coffee beans undergo changes such as:
- Reduction of moisture (from 12-8% to 5-1%)
- Reduction in weight (15 to 20% due to water evaporation)
- An increase in volume (by 30 to 60% due to the formation of carbon dioxide)
- Color change (the grains are brown-skinned) change in content (+12 -16% fats, -10% sugars – acids 3%)
- Development of fragrances
These changes are gradual and are determined by the increase in firing temperature.
- 50 ° C: internal modification of tissues begins
- 60 ° C: the evaporation process begins
- 100 ° C: first color changes come about
- Between 150 and 180 ° C: stage light roasting
- Between 200 and 230 ° C: optimal degree of roasting
- Between 215 and 220 ° C: light roasting (more acidic and less bitter)
- Between 220 and 225 ° C: medium roasting step
- Between 225 and 230 ° C: dark cycle (bitter and less acidic)
After roasting, coffee beans are rapidly cooled to ensure internal condensation of aromatic substances.
There are two methods of cooling:
- Cold air flow, rapid cooling.
- Loss of some perfumes.
- Produces fumes
- Thin spray in precise quantities.
- Reduce several perfumes by opening the pores of the fruit of the coffee.