What factors contribute to differences between coffee beans?

Question

I heard that there are different kinds of coffee beans, which have different specialties like aroma, taste, flavor. But I don't know what causes these differences.

What are the different types of coffee beans, and what are there characteristics? What other factors contribute to differences between one bean and another?

Answer 1

As has been mentioned, the species of coffee makes a difference. There are something like a hundred different species, with Robusta and Arabica being the most common commercially grown by far. Liberica is another species that is grown in small quantities and has a very distinctive taste.

Within a single species such as Arabica, there can be a huge number of varietals. Some are naturally occuring (such as Bourbon and Typica). Maragogype ("elephant bean") is also a naturally occuring mutation from Brazil. Others have been bred by research institutes. For example SL-28 and SL-34 are common Kenyan varietals.

Another famous varietal is the "Gesha" (sometimes romantically but incorrectly called "Geisha"). This came to light when an estate in Pananma "La Esmarelda" noted something interesting when they were cupping their coffee. By separating their harvest, they finally identified a small section which was contributing to the overall cup. This coffee went on to dominate the Cup of Excellence competition and set a world record price at the time. It's since been planted on other farms which brings up the next point.....

As has been mentioned, things like altitude, soil and micro-climate affect the taste. So the Gesha (or any other) varietal from one farm won't taste exactly the same as Gesha from another farm.

The way of preparing the green beans - washed, dry-processed, or a number of other methods, all have their effect on the final flavour. So even the identical cultivar harvested from the same farm but prepared differently will produce different flavours. (The difference between dry and wet-processed is very signficant.) The actual care taken during preparation is also hugely important - I suspect that if one is starting out with a decent high grown bean, this is what really separates speciality coffee from the mass produced stuff. It takes a lot more care to prep the coffee carefully.

And I haven't even mentioned roasting and brewing....

I think this is what makes coffee so interesting - there is so much variety to try and enjoy.

Answer 2

There's a lot to your question; some of the topics have been covered in other questions. Hopefully this will give you some pointers, or help you refine the question to something more specific!

The two primary species of coffee are Robusta and Arabica, as explained in the question linked in comments above. There are also other more obscure species, such as Liberica; see this question for more. There are also various regional strains that differ more subtly from each other, also discussed at the latter question. More on varieties at Wikipedia.

But there are other aspects to coffee besides species:

• regional differences: a coffee grown in one growing region is different from other regions (akin to a varietal of wine grown in, e.g., France vs. California). One q/a with some quantitative data. Here's one of my favorite articles on growing regions and characteristics from Serious Eats.
• peaberry coffee: occurs when one bean grows in the fruit instead of two beans; different shape and qualities. Something around 5% of every crop is peaberry; sometimes the peaberry beans are left in the mix, sometimes they are sorted and sold separately.

And a lot of other factors... :)

Answer 3

Disclaimer: OK, as hoc_age has edited this question, I would like to contribute to this new version. Still, this is quite a broad topic, in my opinion. Maybe everybody in the community may share a part of their knowledge to build a comprehensive list. Thus, we can add iteratively on top of each other's knowledge.

My first try to classify beans is by their origins in a broad sense. Please correct me if I'm wrong.

African beans: These beans are mostly Arabica beans the flavors you taste are generally Mediterranean fruity notes like grape, orange or raspberry. These beans are mostly mild.

Asia-Pasific beans: These beans are mostly Robusta (Geographically, less mountains). They are not aromatic at all, but generally have some earth-like flavors. They are full bodied, strong beans.

American beans: These beans can be either Arabica or Robusta. These beans are also aromatic as African beans but the notes are quite sweet. Generally you taste cocoa, nuts, caramel, chocolate, etc. These beans can have mild or strong body.

Answer 4

There are several factors that affect differences between coffee beans. I'll list them in order of occurrence since the influence factors of each are greatly debated.

• Genetics: There are several species and varietals out there. These vary from major differences between species (arabica, robusta, liberica) to more subtle differences between varietals.
• Growing Conditions: Plants with the same genetics, but grown in vastly different climates will have differences in flavor. Humidity, rainfall, elevation and temperature all have their say with a set of plants. Coffee is ultimately an agricultural product and will vary accordingly.
• Processing: There are a variety of processing methods. Dry Process, Pulp Natural and Wet Processing will all produce different flavor results with the same beans. Different methods are more accessible or more/less useful varying by region.
• Roast Method: Flavor profiles may also vary by roast method. Air roasting and contact roasting may highlight different notes in coffee.
• Roast Level: The level to which beans are roasted (along with how that level is reached) is the last factor to affect the bean.

Arguments could also be made for storage, but I would generally dismiss it as storage has optimums that are meant to keep flavor, but can't really enhance it in any way.