There are a multitude of conditions, such as high elevation, the presence of shade, and levels of soil drainage, that can slow down the growth process of coffee plants. In turn this causes various sugars in the coffee cherry to develop over time, and subsequently impacts the flavor as it sundries into the coffee beans.
Additionally, slower growing processes can alter the density of the coffee beans. High bean density leads to higher heat resistance, which is an indicator for the roastermaster to consider when conducting Split Bean Analysis as part of roasting procedure. (Split Bean Analysis literally means cutting a sample of coffee beans in half, and assessing its density as compared with other beans and other roasts.)
Generally, lower grown coffees have a different solid bean structure than higher grown coffees. As the elevation increases, so does the bean structure. This is caused by the different natural gasses that exist inside the beans as they grow. Additionally, the drainage in the soil helps maintain lower water levels, which keeps cherry size smaller. This applies to mountain grown coffees, because many hilly farms contain plants that grow on a sloped angle, allowing for greater levels of drainage.
Variations in Altitude Around the World
Although there are many diagrams that breakdown coffee flavor based on altitude, they are not always accurate. Coffee grown at the same altitude, but in different parts of the world can show vast differences in flavor profile. For example, some coffee flavor charts state that coffee grown at 5,000 feet or more will show signs of fruity, floral, or spicy notes. Yet some coffees, at the same altitude in Nepal may show salted caramel, and rich creamy notes.
High grown beans in Costa Rica are far different from high grown beans in Ethiopia. Costa Rica's highest coffees are grown around 4,500 feet above sea level, where in Ethiopia they are grown around 6,000 feet. Hawaiian coffee beans are usually found at a lower altitude like most other island-grown coffees: however the difference in flavor may surprise you. Hawaiian coffees are shade grown, which slows maturation of the plants, letting more sugars develop on the coffee cherry, resulting in sweet tart flavor profile.
Higher density beans may take a high initial heat when roasting to help excite the beans to crack. On the other hand, lower grown coffees may have a quicker reaction to heat, so it is advised that you use lower or softer roasting methods depending on bean origin.
There are a lot of things that may impact and change the flavor profile and the density of coffee beans. Our prime recommendation is to try and measure the density before you roast a new coffee. Get to know the coffee beans next to the other coffees you have worked with. This will help you recognize the different nuances of the beans over time, and as a result make you a better roaster.