Red Cherries to Green Beans

Red Cherries to Green Beans

23 February 2016

While visiting a winery in Africa recently, I learnt that in wine, the thickness and colour of the grape skin directly affects the flavour of the wine. This got me thinking as to whether there be any parallels here with coffee. After bouncing this off one of my colleagues, he referred me to OCR (Operation Cherry Red) where certain coffee wet mills only accept red cherries for high quality batches. In doing this and by regulating the drying and consequent fermentation, a consistent profile highlighting a sweet, strawberry flavour is the result. Finding information or evidence on people measuring the thickness of the coffee fruit’s skin was harder. The point was also raised as to whether it is the outer layer of the cherry that affects the sweetness or is it that the inner parchment layer acting as a block, or maybe both?

As our curiosity drove us to seek more information we began our search for a better understanding of the effect of cherry skin versus parchment on sugar retained in coffee beans. In searching online I also tried to build a better understanding of the biology of the cherry and the way cherries are formed. I learned of the stages of growth the cherry goes through, starting with rapid expansion of the locules (a vacant cavity inside the cherry), followed by the growth of the endosperm (coffee bean base material) that fills the vacant cavity. In the next ten weeks of growth the bean will rapidly grow, taking up to 70% of the trees nutrients going to the cherries. Around five weeks later, when the bean is fully formed, the cherry will ripen going from green to red and will be ready to harvest.

I believe the answer to my question lies somewhere in this development period. One agronomist we spoke to was not convinced that sugar is transferred from the coffee mucilage (‘fruit pulp’) to the coffee seed (‘bean’), but rather it is intrinsic to the bean itself. As opposed to this opinion, many years ago while working on a coffee farm, Instaurator tasted coffee that had been processed in an unusual way, as the result of a violent wind storm which stripped the fruit from the trees. The fruit was then left on the ground for several weeks. The coffee itself tasted wonderful, much like a Guji style coffee only richer, deeper, earthier with plum-like fruitiness. It would seem that the beans (‘seeds’) in this case had absorbed some extra character as a result of the fruit and or skin even though is was not verified. Whether it was the skin per se, is definitely hard to quantify.

So if anyone has read or researched anything on this topic I would be very interested in their data-based observations.

Caleb Holstein
Apprentice Coffee Roaster
Espressology
Sydney, Australia