In the coffee world there is a received wisdom: the higher, the better. Altitude alone is often spoken of as if it were proof of quality. As a coffee lover, I do think a little more altitude "sounds delicious". And as a farm owner, a little more altitude makes me a little proud. But this wisdom should be restated more precisely. Let me check it against the research.
There is a study that measured the relation between altitude and quality down to chemical composition. As altitude rose, green-bean pH fell, the chlorogenic acids behind bitterness fell, and sucrose, the precursor of sweetness, rose (correlation coefficients with altitude of R = −0.85, −0.94 and 0.91 respectively; the closer R is to ±1, the stronger the relation. Urugo et al., 2024).
The important point is that the total amount of acid correlated with temperature rather than rising with altitude alone. "High = acid" is about pH (the strength of acid), a different matter from the total amount. The same word, acid, was pointing at different things.
It is becoming clear that what governs quality is the coolness of the temperature rather than altitude itself. When it is cool, ripening proceeds slowly and sugars and aroma precursors accumulate. One report found ripening extended by about four weeks in a cool environment compared with a hot one (Cassamo et al., 2022; Ramalho et al., 2018).
Altitude is only one condition that brings that coolness. At the same altitude, different night temperatures and diurnal ranges give different results. So it is more accurate to speak not of "how many metres the farm is" but of "how cold the nights get in that garden".
In low-latitude Southeast Asia, where we are, the same altitude is warmer. In measurements from low-latitude Indonesia, beans from 700 m scored around 80 in cupping (SCA, out of 100) while beans from 1,250 m scored 82 to 84, a difference that crosses the specialty line. Sucrose, the precursor of sweetness, was about 2.4 times higher in the 1,250 m beans than in the 700 m beans (Nugroho et al., 2020). To aim for specialty at low latitude, roughly 1,200 m or more is the guide.
The other way to take the heat off is shade. Compared with full sun, shade lowers the maximum temperature by 3 to 5 °C and slows ripening (Koutouleas et al., 2022). The hotter the plot short of altitude, the greater the worth of shade. Altitude cannot be changed, but shade can be designed (though it needs a long-term plan).
I am tempted to say "we do not make altitude a signboard of quality", but honestly, the farm cannot be moved and new land is not easily acquired. The conditions in which higher is advantageous are certainly in place.
That said, my feeling is that a farm designed so that the diurnal range and the way shade falls can be controlled does more for the filling of the fruit. Altitude is a given; temperature can, to a degree, be made. So what we look at is how slowly and evenly the fruit ripened on that land.
Altitude is an easy number. That is why it becomes a signboard. But the same altitude tastes completely different. What makes the difference is the cold of the night, the diurnal range, the shade, and the slow ripening that results. Precisely because it is not simple enough for one number, measuring and recording has meaning.
Not exactly. pH (the strength of acid) falls with altitude, but the total amount of acid correlates with temperature and does not rise with altitude alone.
In measurements from low-latitude Indonesia, 700 m and 1,250 m gave a cup difference that crossed the specialty line. Roughly 1,200 m or more is the guide.
Shade works. Shade has been shown to lower the maximum temperature by 3 to 5 °C compared with full sun and slow ripening. The hotter the plot short of altitude, the more shade is worth.
For reading ripeness beyond colour see Signs of ripeness beyond colour; for the risk of over-ripeness, The upper deadline of ripeness; for the whole picture, Harvest and selective picking; for measuring and telling, What is the Data Bank.
New records and lot releases, delivered to your inbox first.
New lots, drying updates and field notes — every Friday, in one short letter.