The flavor of green coffee can change dramatically over its lifespan, from the moment it is harvested until it is roasted. Even very fresh coffee — with impeccable processing, expeditious exporting, and careful roasting — is several months “old” by the time it hits the grinder.
Since the coffee is changing all throughout this time, it is important for cuppers — especially in the world of coffee buying at origin — to learn how these changes happen and what flavors are associated with them.
Traditionally, most coffee is “rested” after processing, in warehouses within the country of origin. So this means, for example, that coffee from Guatemala that was harvested in February might finish drying in March, and then be placed in a warehouse with the parchment still on, where it sits undisturbed for as long as three months!
Then the coffee must be milled, bagged, and shipped. By the time it reaches Asia, for example, it could be almost August already — almost six months after it was harvested. And this is considered fresh crop coffee.
Coffee treated in this manner is still quite excellent and fresh. Indeed it is probably “peaking” in terms of flavor. So there’s nothing “wrong” with this old model. But there’s a better way to do things. To understand how, we need to look at why producers developed the practice of resting coffee to begin with.
Proper Drying Practices and Free Moisture Distribution
When coffee first comes out of fermentation tanks while processing, the free moisture content can be well above 40%. Properly dried coffee ends up with a free moisture content of somewhere between 10% and 13%, with most producers aiming for that 12 – 12.5% range. This is free moisture content, which means water that is not chemically bonded within the cells of the bean: moisture that can move around, evaporate, or increase depending upon conditions.
However, it’s not enough just to bring down the overall percentage. The drying process must also maintain a relatively even distribution of moisture within the structure of the bean.
Imagine if you lay the wet coffee out on a patio, and never move it around. The sun will beat down on one side of the coffee, while the underside might be totally hidden from heat, and the water on that side of the bean will not evaporate.
In this case you might have 20% moisture on one side, and 7% on the other. The overall reading will be around 13%, but it’s totally unacceptable. Imagine roasting this coffee. One side will be under-roasted and raw. The other side will be over-roasted and burnt. Even with excellent roasting technique, you will end up with bad-tasting coffee. (This, of course, is why drying is so very important!)
With better drying practices, the coffee moves during the drying process, and air moves all around the bean too. Carefully done, we end up with beans that look more like this:
As you can see, the moisture is much more evenly distributed. This is far superior to the first case.
However, if you notice, the moisture is still not perfectly distributed. There are small pockets of extra moisture, and small pockets that are slightly more dry. Coffee is a living, breathing organism, even after it has been harvested. There is no such thing as exact perfection. But with this carefully processed coffee, we are off to a good start.
Now, if you are traveling at origin at the end of harvest, looking to buy some great lots, this is what the good coffee will be like. It will be well-dried, with relatively even moisture distribution — but that distribution will still not be totally even.
Of course, you can’t see any of this. You can’t even measure it with a moisture meter, because such devices can’t give you such a fine level of detail. You have to be able to taste it on the cupping table.
Why “Rest” Green Coffee?
There is a particular character to coffee that is very recently processed, and it’s related to several factors. Aromatic compounds are more densely packed and present than they will be at any other point in the coffee’s life cycle — as the coffee respirates over its lifetime, it will gradually lose aromatic intensity. Also, as you can gather from the above linked video, some chemical changes are still happening, especially with natural-process coffee.
Another associated flavor is a bit of “green-ness,” “freshness,” or “youth” in the coffee. “Young” coffee means coffee that has not been rested in the warehouse for very long.
A few days after the drying is finished, the moisture is still moving around within the coffee, even for beans that were treated perfectly. Eventually, as the different parts of the interior of the bean exchange free moisture, it will even out more and more.
Of course, this is only a schematic drawing. The coffee will probably never achieve perfect, exactly even moisture. But it’s much closer to even after resting for several weeks.
But resting alone cannot save coffee. Imagine if we took the improperly dried coffee that we first looked at, and then rested that. What would be the result?
It’s still a mess. You can’t hide bad quality just by resting it.
However, resting coffee will make good coffee taste smoother, sweeter, and less “green.” This is why many producers, and especially many exporters, will rest their coffees before trying to sell them. Cuppers are more likely to score the rested coffees higher.
Young coffee tastes a little bit like under-roasted coffee. It has a fresh, green character to it, due to all of the above factors.
Tasting Into a Coffee’s Future
Of course, experienced coffee cuppers and buyers can learn to recognize this flavor. Once you have tasted it many times, you begin to be able to “taste past” the youth of the coffee. Also, it is especially helpful to have an opportunity to taste a coffee when it is young and when it is rested. That way you build an internal understanding of how the coffee will change over time. If you do this enough, you begin to develop a skill for tasting into the future of the coffee — understanding how it will taste even before those tastes develop.
Unfortunately, the vast majority of coffee professionals simply never get this chance. Producers may usually only taste their coffees when they are young. Roasters — even master roasters with tons of experience — probably taste very few truly young coffees in their careers.
Learning about youth in coffee and how it develops over time has been a steep learning curve for me personally, but the more we get a handle on it, the more it frees us up to buy very fresh coffees that are still exploding with flavor. We can trust our ability to pick great coffees and also get them into the hands of developers as soon as possible.
If we discover a coffee in March, we think it’s best to immediately set in-motion the process of exporting it. It can “rest” as it’s being prepared for export, shipped, and warehoused. This extends the life cycle of the coffee at the developers’ end, and we want to put as many choices into the hands of developers as possible — if a roaster wants to rest something, great! But the roaster ought to be given that opportunity.
Learning how to taste young coffee at origin is a skill that can be learned, as I said. It’s something we’re also developing a language to talk about within OCN. We want to be able to share knowledge across the board, from origin to developer to the final cup.
We’ve already started our concierge service, allowing you to tell us what kind of coffees to seek out at origin. In the future, we want to also extend things even further, and help roasters, baristas, and other developers make their own choices directly at origin. At some time in the not-so-distant future, we will be sharing thoughts on tasting young coffee with developers in-person … in Africa, in Brazil… who knows?
If you’d like to start a conversation about being included on future OCN origin trips, drop us a line at firstname.lastname@example.org.