Ideally, after the washed process, the parchment should remain surrounding the bean for 15-90 days. This strengthens the cell structure of the green bean and extends the shelf life of the green coffee. The parchment, or endocarp, serves as a protective barrier for the coffee to help maintain more consistent moisture and keep unwanted flavors out. Coffees that are removed from the parchment too soon often age faster once they are shipped. Taking the time to rest coffee is a challenge for producers because they have spent the money to fertilize, pick and process the coffee and are often strapped for cash by the time they should be letting the coffee rest.
Prior to the resting period, or reposa in Spanish, producers dry the coffee in parchment until it reaches 10-12% moisture content. Maintaining the moisture level for the remainder of reposa, like so many aspects of processing coffee, proves more complex than one would expect. If moisture levels in the coffee increase during this time, the quality of the coffee may suffer. The resting facility design must accommodate the requirements of the coffee in parchment. Coffee needs to rest in a cool, shaded and dry area since exposure to hot humid air causes it to reabsorb moisture. A lot of fluctuation in the temperature of the structure itself can lead to interior condensation and a subsequent undesirable increase in humidity, so a building with temperature stability is preferred.
To further complicate matters, coffee in reposa also needs ventilation. Producers must maintain a delicate balance between moving the air through the building to allow the coffee to breathe and stabilizing the temperature and humidity. Often, jute bags filled with coffee resting in parchment are stored in a large mass stacked together on pallets which limits the total surface area of the coffee that comes in contact with the surrounding air but still allows the coffee to breathe. A more advanced storage technique utilizes a bin or silo. Humidity controlled air moves slowly through the coffee using a standard fan in a process called conditioning. Heat rises, so a fan placed at the bottom of the bin or silo can help maintain the temperature. The size and resources of the farm or washing station, climate at origin and established way of doing things locally all influence the many ways to achieve a balance between ventilation and control of temperature and humidity.
Although we believe that the ideal rest period is probably 60-90 days, we have learned that is it also important to keep in mind the rest of the journey for that green coffee. After resting, the coffee goes through an arduous journey to the dry mill where it is hulled, sorted and prepared for shipment. It is important to ship the coffee as soon as possible after this barrier is removed at the dry mill. The coffee is taken to a port at sea level in the tropics (too humid), then loaded on a boat, and often stuck in transit going through the Panama Canal (also humid). If it can take up to 2 months in transit to the USA, do we really want to add another month of rest? Is fresher coffee, unrested at origin and shipped to us sooner, a better choice?
The ideal rest time must be balanced against the amount of time that it will take to get to America. We often now begin preparing coffee for shipment after 30 days rest time in order to ensure fresh arrival.
Time from Coffee-on-Boat to USA port
- Central America 2-4 weeks
- Ethiopia/Kenya 3 months
- South America 3-5 weeks
- Indonesia 4-6 weeks