Dry Milling

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Dry-Milling (general aspects)

Dry milling of coffee is the process by which the husks are removed from the beans so the beans may be sorted and classified by size, weight and color.

When designing a dry mill, a number of factors are taken into account. The coffee beans will be sorted and classified by size and weight. Some customers specify the size of the beans and the amount of defects they will allow, such as not allowing any black or broken beans.Elevadores

Dry milling Process

About 80% of the coffee beans can be classified through the following means:

Using an air elevator (seen at left), all heavy foreign objects such as stones or any metal are removed as the coffee parchments float up the required height into the thresher.

The coffee parchments are placed into the thresher to separate the husks from the coffee beans. The husks are set aside for later use, and the coffee beans continue on through the milling process. There are two methods to separate the husks from the beans. One uses friction and the other blades. The friction method is called “Peladora”, (lower right photo) where the parchments are placed between rollers and the husks are stripped from the coffee bean. The second method uses blades to cut the husks from the beans.

Peladora

The coffee bean is then categorized by size and weight by sorting them through a series of sieves of decreasing size (photo at bottom left).

The sorting method continues by using vibration and air flotation to separate the beans by three qualities, heavy (1st), medium (2nd), and light (3rd). Eco-Delight Coffee uses only heavy (premium) beans.

The coffee beans are stored in hoppers or silos until later when a stricter classification by color is done. Off-color beans are removed using an electronic sorter.  The remaining beans then continue on a conveyor belt where skilled workers remove any remaining defects.  The next step is roasting.

Clasificador cilíndrico

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