Going to purchase coffee seems like it is becoming an increasingly confusing task each day, what with the huge selection now being offered, with varieties from around the world that all claim to be the very best. You have organic coffee versus non-organic, estate coffee versus blends, and oftentimes a choice between Arabica beans and Robusta beans. The following is a brief breakdown of some of the most important differences between the two species to help guide your purchasing decisions.
Let's begin with the difference you probably care about the most, taste. Arabica beans come in a much wider range of flavors. The mildest varieties are soft and sweet and the most robust are tangy and sharp. Before they are roasted they give off a scent that is oddly berry-like, and roasted they take on a bit stronger of a sugary sweetness. Robusta beans have less variety, and though delicious Robusta coffees are certainly out there, many find the taste to be a bit harsh and less complex.
Robusta coffee is considered a much hardier plant than Arabica, because it can stand up to surprisingly harsh environments, including low altitudes, hungry insects and other pests, as well as rough handling. This makes it quite cheap to grow in large quantities, and thus very available at much lower prices. Arabica coffee is a bit trickier. These plants crave cool and moist (usually subtropical) conditions, and are only found at much higher altitudes. Usually somewhere between 600 and 2000 meters is the right elevation. They require both shade and sun regularly, and though they like the cool, they will wither in the cold. It is because of these conditions that they are often lower in acidity, and therefore less bitter. A perfect example of a region made for growing Arabica is the Jamaican Blue Mountains, where the world famous Jamaican Blue Mountain coffee is grown.
Because Robusta beans are so cheap and easy to grow, if you pick up a can of coffee at the grocery store, you are often getting more robusta than arabica. A higher quality blend from a specialty shop or a gourmet coffee purveyor will most likely contain a high percentage of Arabica. It is not, however, necessarily as simple as Arabica being better. Once of the most defining qualities of this species is its range, so many coffees and coffee blends of this type may be inferior to certain Robusta selections.
Robusta is used in many European espresso blends to both increase the "crema" and lower the cost of the coffee. Used sparingly, it will not hurt the flavor much, but too much Robusta means a less complex espresso.
Unfortunately, this means you still may have some research ahead of you in your quest to choose the right brew for you! As a rule of thumb, though, the best coffees are not blends at all (so nothing you do not know about can be snuck in there), and will be labeled saying exactly where they are from.