Coffee News: from Seed to Cup

Coffee Quality & M.A.S.L.: How Important Is Altitude REALLY?


Pick up any bag of artisanally roasted specialty coffee and have a look at the label. You’ll notice it tells you a few things: the country of origin and the region, what tasting notes the beans have, perhaps the name of the farm or roaster… and, if it’s a single origin, it will normally also tell you its altitude, measured in metres above sea level (m.a.s.l.).

But what does this actually mean? As coffee lovers, consumers, and perhaps even coffee buyers or roasters, why should we care about it?

Well, if you ask the barista, they’ll probably tell you that higher-altitude coffee is higher-quality but actually, it’s a little more complicated than that. Let’s take a look at what altitude really means.

Lee este artículo es español ¿Qué Tan Importante Es La Altura Para La Calidad del Café?

coffee farmView from a mountainous coffee farm in Colombia. Credit: Angie Molina

Altitude: A Symbol of Coffee Quality?

Higher altitudes are associated with sweeter, more complex coffee flavours, but it’s actually correlation, not causation. The real cause of this better-quality, more delicious coffee is temperature.

At lower temperatures, coffee trees will grow more slowly. The cherries that contain the seeds we roast and call coffee beans will also ripen more gradually. This means they have more time in which to develop complex coffee flavours.

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(On the other hand, there are downsides to this: coffee trees can yield less fruit, require more care, and harvest later in the year. Coffee shouldn’t be grown in too warm a climate, but neither should it be grown in one that’s too cold.)

coffee farmMountains in the distance, viewed from a coffee plantation in Nicaragua.

Even More Reasons Cooler Temperatures Are Good

At these cooler temperatures, it can also be harder for certain pests and diseases to thrive. Take coffee leaf rust, a fungus that attacks the leaves of coffee plants, thereby preventing them from photosynthesising and getting the energy required to grow healthily. In 2012, it devastated Latin American coffee communities, causing over US $1 billion in just two years (USAID). Yet, as Emma Sage, SCA Science Manager, makes clear, leaf rust is not without its own vulnerabilities – and one of these is temperature.

In a 2012 SCAA blog post, Sage writes that the optimal temperature for coffee leaf rust is 21–25°C/70–77°F while the disease cannot survive at less than 15°C/59°F. The ideal temperature for growing coffee in is 17–23°C/63–73°F, while it can be grown less effectively at 14–30°C/57–86°F.This means that, at lower temperatures, coffee leaf rust should be weaker.

Similarly, the coffee berry borer has caused hundreds of millions of dollars of damage, and it thrives at a warm 20–30°C/68–86°F, according to a 2009 study.

Coffee farms outside of this range (which normally means at higher altitudes) are less likely to be affected by coffee leaf rust, the coffee berry borer, or any other pest that struggles to survive in cooler climates. This adds up to fewer defects, and in turn fewer unpleasant flavours, in the final cup.

Not all coffee varieties are susceptible to rust; however, those that aren’t can sometimes have a less desirable taste. This is because they normally have a Robusta parent, a hardy yet bitter coffee species. A lower risk of pests and diseases also encourages some producers to plant higher-quality yet less resistant varieties (another thing that you might be able to find out from the coffee bag label).

Want to learn more? Read A Crash Course in Coffee Varieties

However, explaining all of these complexities takes time and a patient listener. For all these reasons, when asked why altitude is important, we tend to simplify matters and just say that higher altitudes produce better quality coffee.

The problem is that sometimes they don’t.

coffee farmView from Colombian coffee farm. Credit: Angie Molina

Where Altitude Falls Short

Just as altitude affects temperature, so too does latitude. Take a country like Colombia, famous for its high-quality, high-altitude coffee. Farms in regions like Nariño are barely 100 miles from the equator and, according to the Colombian Coffee Growers Federation, sit at 2,300 m.a.s.l. The result? High acidity, sweetness, a pronounced aroma – all of which adds up to a spectacular coffee.

But if we head to Cerrado Mineiro in the south of Brazil, over fifteen times as far away from the equator as Nariño, we find that the farms are at much lower altitudes: between just 800 and 1,300 m.a.s.l. And according to The Association of Brazilian Coffee Producing Regions, the area’s average temperature is 23°C, placing it within the ideal coffee-growing conditions.

So why should we look down on a coffee grown at just 1,100 m.a.s.l., when the local temperature will still be relatively cool?

Nor is it just latitude that can affect the local temperature. The Galápagos Islands straddle the equator, with farms at just 200–300 m.a.s.l. Yet the temperature is similar to that of Cerrado Mineiro, thanks to the Humboldt Current bringing cold air up from Chile and Peru. Coffees from here tend to be sweet and medium-bodied with caramel notes.

Altitude is an unfair scale. While it can indicate coffee quality, without the right context – a knowledge of latitude, local climate, and more – it can become meaningless. It’s useful when applied to farms in a specific region but should not, for example, be used to compare Hawaiian and Venezuelan beans or Indonesian and Yemeni ones.

So why do we rely on it instead of temperature? Because, unlike altitude, temperature fluctuates by the season, day, and even hour. And even if the scale is imperfect, we need to know how quickly the coffee beans grew. It affects the coffee’s flavours, aromas, and ideal roast profile.

coffee farmCoffee plantation in Brazil. Credit: Ana Valencia

How Does “Altitude” Affect Coffee Beans?

Roasters have a better way to measure this concept of coffee grown at low temperatures or high altitudes: they talk of density or hardness. Beans that develop slowly are hard or high-density; those that develop quickly are soft or low-density. Unfortunately, the coffee industry has no unit of measurement for density (some countries describe coffees grown above a certain height as Hard Bean or Strictly Hard Bean, but this goes back to the original problem: the ideal altitude will vary across countries and regions). However, the idea of measuring density does break the connection between altitude and quality.

This is because roasters, even more than coffee buyers, baristas, and consumers, need information about a bean’s density. You see, developing slowly doesn’t just result in more complex flavours; it also affects the bean’s physical composition.

As Zach Daggett wrote for Perfect Daily Grind in 2015, green, unroasted beans that are low-density tend to have an open fissure line. Those that are higher-density have a closed fissure.

But if we were to look inside the beans, we would see even greater differences: the low-density beans have more air pockets. This means that, during roasting, heat will be transferred more slowly and erratically. As of such, roasters should use a lower temperature to avoid burning or scorching the beans.

Discover how to roast hard and soft beans!

coffee farmA coffee farm in Brazil. Credit: Julio Guevara

Altitude: Just One Part of The Coffee Quality Equation

Are we, if you’ll pardon the pun, making a mountain out of a molehill? Is altitude really that important?

Coffee quality is complex. It’s affected by many factors: the coffee species and variety, the farming and processing methods, soil quality, altitude, local climate and how it varies from year to year, storage and export conditions, roasting, brewing…

Yet how quickly or slowly a coffee cherry develops can have a significant impact on the coffee’s flavour when brewed (not to mention how it’s roasted). For this reason, altitude is a valuable thing to know. We just need to understand in the context of the latitude and local climate.

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Written by Tanya Newton.

Perfect Daily Grind

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