What is Coffee?
First of all, coffee is a selectively picked crop, just like strawberries, apples, or lettuce. It comes from a tree or bush in the ground, and it has a life cycle: it grows, peaks, matures, and declines. When the crop is gone, it is gone for good. No two crops are exactly alike although generalities do persevere year after year.
There are two main species of coffee trees: Arabica and Robusta. Arabica trees produce less coffee per tree than Robusta and they require more attention; that equates to higher prices. They also produce the more flavorful beans and are known as specialty coffees.
There are a number of subspecies of Arabica, perhaps the most common being Typica, Catuai, Caturra and Mocca. Hybrids and sub-species also abound, like Maragogype, Bourbon and Pacas to name a few; they are all Arabica plants.
Robusta is a high-yield, low maintenance tree that produces beans with less flavor and lots of caffeine, much more than Arabica varieties. They are used primarily as inexpensive fillers in commercial coffee, sold to soft drink bottlers as a caffeine source, and used sparingly in many peoples' Espresso blends. That being said, virtually everything else written here will be about the Arabica species.
Where and How Does Coffee Grow?
Coffee production usually occurs in the tropics. With rare exception, coffee trees grow between the Tropic of Cancer and the Tropic of Capricorn all around the globe. There are many factors that impact the flavor of each crop, including soil condition, sunshine, and precipitation.
Other factors are the amount of shade the trees have:
- More shade means slower ripening process means more qualities are drawn from the soil and the air.
- How the trees are pruned makes a difference, as with any fruit bearing plant.
- What kind of fertilization is used: chemical or organic.
- What method of pest control is used: chemical or natural.
What are "HARD" and "SOFT" coffee beans?
First of all, "Soft/hard bean" is a new kind of descriptor and somewhat nebulous. It seems to have come from someone with more knowledge of engineering, electronics, and physics than coffee beans, and I think the Hearthware engineers were merely trying to describe the best use of their different pre-programmed roasting profiles
To the best of my knowledge these are relative terms, and there is no hard and fast definition of hard or soft beans that I am aware of. There are a number of variables that lead me to consider one bean harder, or softer, than another, but it is a relative term.
It could refer to bean density, which is largely dependent on moisture content. Moisture content is largely dependent on variables like freshness, diligence in processing, storage, and other ambient conditions...and subject to change. This is easiest to see in a bean fresh off the tree versus the same bean a year (or more) later.
Some arabica subspecies are generally considered harder or softer. Typica beans, i.e. Jamaican Blue Mountain, most Konas, some Colombians and Indonesians, tend to be "softer," and I often refer to them as "fragile" in a number of descriptions. Others, like Catuais and Moccas, could be considered "harder beans," which tend to take a dark roast well without burning.
Peaberrys are also generally considered harder then bi-valved beans, regardless of their subspecies. Kona Peaberries are harder than Kona XF (Typica), and Kauai Peaberries are harder than Kauai Estate Reserve (mostly Red Catuai); the old Maui Mocca Peaberries were harder than the Maui Mocca 14 screen (Mocca).
The term "hard bean" has also been attributed to beans grown at higher elevations, and we frequently see the term "SHB" attributed to Latin American coffees grown at altitudes over 3000. The implication is that lower grown Latin American coffees are softer, although I have found no appreciable difference in how they roast.
The only decisive answer, in my opinion, is the terms are relative. To the best of my knowledge, there are no published parameters.
The question now becomes where to draw the line between what is hard and what is soft.