Sorting Coffee Beans 

For coffee grown and processed in South American coffee beans, each batch picked must be sorted by both density and color.  For density, the small, unripe, broken, or any kind of defective beans are removed.  Keep in mind that to catch all the bad beans, there are generally up to three stages of this type of sorting, although two stages are sometimes used. 

For the first stage of density sorting, dense stones and rocks are removed.  Then the second stage is where debris is removed such as leaves, pebbles, and twigs, and the coffee is hulled.  This final and third stage is considered the most important of the three.  For this, a densimetric table for separating coffee into three or more levels of density is used.  The machine has settings that have to be monitored constantly to make sure the sorting process is going according to plan. 

With this, the light and less dense beans will move to the bottom portion of the table and the higher quality coffee beans to the upper third portion of the table.  Next, the table removes any remaining debris that was missed.  Keep in mind when buying South American coffee, the coffee beans that have gone through all three stages are the better tasting beans. 

Now, the coffee beans must also be sorted according to color.  Again, this process is used commonly for removing debris not caught during the hulling or processing processes.  Interestingly, many South American countries still color sort beans by hand simply because the labor to do so is so inexpensive.  However, some countries use modern day machines, typically made by Xeltron and Sortex. 

Similar to the hand sorting, the machine uses a CCD camera system to measure the color of each bean.  Then, depending on the wavelengths that have been measured, the bean will go down to the bottom portion of the table or to the top.  Other beans that do not fall into the right category, or are considered defective will be shot into a reject pile with a powerful puff of air.  For black and white coffee beans, these must be sorted with special monochromatic machines that are more sensitive to hue.