Coffee Roasting

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The Process of roasting coffee

To roast coffee means to heat the beans in a roaster to reduce moisture. Initially, the beans have a moisture content of about 12%. After roasting, the moisture content is  less than 1%. The beans start out a green color and darken during the roasting process. Once the coffee beans have been roasted, they are ground for packing or for brewing.

Roasting plants

Plants to roast and package coffee can be small, medium, large or mega size.

Roasting plants are classified by the amount of coffee they can roast. A small plant has the capacity to roast between 2 and 50 kilograms (5 – 100 pounds) of coffee per hour. Medium size plants can roast between 50 and 100 kilograms (125 – 250 pounds) of coffee per hour. Large plants can roast between 100 and 400 kilograms (250 – 1,000 pounds) per hour. Mega plants can roast more than 400 kilograms (1,000 pounds) per hour.  Eco Delight Coffee chooses to have a medium size plant in order to guarantee homogeneous consistency in our roasting process; characteristic of our concept of artisan coffees.  Eco Delight Coffee will continue its focus on top quality artisan coffees. Rather than sacrifice quality to achieve economies of scale as a large roaster, we will establish medium size roasting plants when expanding to other locations.

All roasting plants, regardless of size, use the same process. An elevator (usually mechanical screw) separates the coffee beans from any foreign particles or objects which might damage the machines. The roaster (at right) uses a gas burner to heat air which is then blown into the roasting rotating cylinder instead of placing a heating element inside the cylinder. Injecting hot air provides a higher quality roast and prevents damage to the beans. Some countries prefer to add sugar to the beans during roasting to produce more of a caramelized bean. The gas fuel can be either natural or propane gas, or a mixture of both.

After the coffee beans have been roasted to the desired level, the beans are removed from the roasting cylinder and placed into a cooler. The cooler is constructed of stainless steel and has a perforated floor to extract the smoke and hot air which surrounds the beans. Cooling takes between 4 and 6 minutes. Once the beans have cooled they are moved to a pneumatic elevator which removes husks. The coffee beans are then placed in a hopper to rest and degass. After the beans have a chance to rest in the hopper, they can either be bagged or ground for future brewing.

Coffee mills (also know as grinders) can be either disc or roller mills. The disc mills are more popular and more economical while roller mills allow for better gradation of the ground beans.

Coffee can be packed as whole roasted beans or as ground beans. In small companies the packing process is manual while in a larger plant the packing is automatic.

Some countries require treatment of the smoke from the roaster. This treatment can consist of a cyclone to separate the particles from the air stream, scrubber, washer or afterburners.

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