September 15,
Richard Jackman, Founder and Coffee Roaster
The journey from the humble coffee plant to your steaming hot morning brew is a long and complex one. In my post back in April, we talked about the coffee plant and the coffee cherry to which the coffee bean (seed actually) hides inside. Today we will have a look at how the cherry gets harvested, and processes involved in getting the coffee bean out of the cherry then getting it ready for roasting.
Coffee cherries mature and ripen individually on a plant and often not all at the same time. For optimum drinking quality, the coffee cherries need to be harvested at a specific maturity so for coffee growers aiming to produce specialty grade coffee, their crops need to be harvested several times within the harvest period. In Northern Peru where our growers are located, the harvest period is between May and August each year. Due to the mountainous topography where coffee plantations are usually located, coffee cherries are harvested by hand. This is a very laborious process as the cherries are very small and must be selected individually, discarding any cherry that has an obvious defect on it (such as insect damage, rots, or under/over ripe).
To get at the coffee bean inside the coffee cherry, there are two main techniques that are used globally: the 'natural' method or the 'washed' method. The natural method is the oldest techniques and simply involves leaving the coffee cherry to dry naturally in the sun to reduce the water content to below 12.5%. Drying usually takes 3-4 weeks. This technique often results in a more sweet cup with complex notes brought in from the fermented skin and pulp and heavier body. However, this technique also can result in inconsistencies in the quality due to the difficulties in sorting our any 'bad' cherries that were harvested, and difficulties ensuring the cherries are evenly dried.
In Peru the natural drying method can not be used as the climate is too wet with frequent rainfall events so the main method used is the washed method. In this method the cherries are first placed in a water bath. Any poor quality or immature cherries float to the top and are removed. Next, the cherries are placed through a de-pulping machine which removes the skin and most of the pulp from the cherry seed. The pulp (mucilage) is very sticky, so to remove the remain pulp from the seed, the cherries are then placed into fermentation chambers (water baths or barrels) and left to ferment for 12-36 hours. Following fermentation, the seeds are then rewashed, which removes any remaining pulp. At this stage the seeds (beans) contain just over 50% water. To prevent any mould growing on the coffee bean, their moisture content must be below 12.5% so the seeds are air dried until they are below this level. Once dry, the beans can then be stored in silos until required.
Drying the washed coffee either under cover or outdoors
The beans that are stored in silos still need a couple more steps before they are able to be roasted. These beans still have a papery protective outer layer called parchment that needs to be removed. This is removed mechanically at the pack-house which reveals the green unroasted coffee been beneath. At this stage the beans can then be graded both mechanically and by hand to remove any defects that are now able to be seen.
Green unroasted coffee beans in their final form before roasting
Once graded, the defect-free beans are then packed into jute sacks which contain special modified atmosphere bags that when sealed provide an environment that protects them from the harmful effects of atmospheric oxygen and humidity. These bags slow the beans aging process considerably, allowing them to stay fresh for up to one year without any major degradation in cupping (tasting) quality.
Finally, the sealed sacks of coffee are then sea-freighted to NZ for use in our roastery. As I said in my first blog, the process of getting from the bean from the plant to the cup is a long and complex one. We are nearly there, but in the next article I will talk about the second to last stage in the journey (and my favorite area): roasting the beans.
