Show me your beans and I will tell you where you are from
Does a bigger bean pack a bigger punch?
Let us begin with the fact that differences in coffee's appearance can already be seen in raw green beans, or even in the fruit. Some coffee cherries are particularly large, with seeds reaching as much as 1.2 cm in length. One example is Brazil's Maragogype, affectionately called “elephant coffee”. This spontaneous mutation of Typica appeared in 1870 on plantations in Bahia, in northern Brazil. Today it is a varietal — a mutation grown commercially — that gives growers and coffee lovers the largest beans, sometimes twice the size of their ordinary cousins. By comparison, the smallest beans can be found in bags of Ethiopian Mocca.
Differences in bean size come from genetics, but also from the natural conditions in which the plants mature. The mineral richness of the local soil has a considerable influence, and a region's soil chemistry tells growers how a coffee shrub “feeds”. But does size always matter in coffee? Well, yes and no. The general view is that, within the same variety, larger beans contain more caffeine. That does not mean their smaller cousins from a different varietal are inferior. Quite the opposite: small beans sometimes contain much more of this stimulating substance! Keep that in mind when choosing a coffee with the strength you enjoy and matching it to a brewing method, whether a traditional moka pot or a modern dripper.
Not just genetics
Genetics has a lot to say about what beans a plantation will produce. By crossing species and reinforcing particular characteristics, growers can obtain beans distinguished not only by size but also by shape — rounder or more oval — and even caffeine content!
One look at a chart of beans from familiar varieties explains why an experienced coffee tester would never confuse a small, almost perfectly round Colombian Caturra bean with a slender Panamanian Geisha. Yet these most visible differences, size and shape, are not only the result of tinkering with DNA. Interestingly, processing matters too. The notably large, swollen Monsoon Malabar beans from Kerala, India, reach their size by absorbing moisture from monsoon winds for three months.
On the trail of flavour
Finally, a few words on what probably interests caffeine fanatics most: do flavour differences between coffee varieties also come from genetics? Of course, but not only from genetics. Processing, during which beans absorb sweet juices from the pulp, and roasting, which draws out their flavours and aromas, also play major roles in shaping a coffee's profile. But why does a particular coffee region almost always produce beans with a particular flavour profile?
Why does your barista always know that Anna's citrus-scented espresso came from Africa, while Stephen's latte, steaming with caramel and chocolate notes, came from deep within South America?
It turns out that some African countries choose dry, or natural, processing because of the local climate and limited water resources. Prolonged contact with the fermenting skin, which comes away after several weeks, infuses the bean with tangy, fruity notes. And the caramel and nutty aromas from countries around the Amazon? Scientists associate these with the mineral composition of the local soil, particularly large quantities of potassium found in areas with frequently erupting volcanoes...
Whether you prefer large, round beans or find their slender cousins more appealing, always look for those that deliver the best flavour. Stay open to beans of every size, roundness and shape. After all, you never know what aromatic riches an unassuming Costa Rican Caturra might hold...