About Coffee and Roasting
Arabica (Coffea arabica):
Arabica coffee plants produce a more flavorful cup of coffee when roasted and brewed. The beans are considered far superior to those from the alternative Robusta plant.
Arabica coffee plants are somewhat delicate. They demand a precise temperature range and annual rainfall, which limits the areas in which they can be grown. There can be no droughts or frosts or the Arabica coffee plants will die. Arabica plants grow more slowly than Robusta, and they are typically grown at high elevations – between 3000 and 6000 feet.
For these reasons, Arabica coffee plants are more costly to grow and consequently the beans the plants produce cost more than Robusta beans.
Robusta (Coffea canephora):
The beans from the Robusta coffee plant can be described as flat and neutral in taste when compared to those form the Arabica plant, but with a higher cafine content(which makes them a stonger taste).
Robusta coffee plants can be grown at low elevations and, as the name Robusta implies, they are very robust – able to withstand weather related problems that would seriously harm Arabica plants. This hardiness means the Robusta plants are less expensive to grow and consequently the beans they produce cost less as well.
Typically, large commercial coffee roasters purchase most of the Robusta coffee bean crops. They often blend their Robusta beans with some superior Arabica coffee beans to impart a better flavor.
The machinery to roast coffee fall into two types, drum roasting & fluid bed roasting.
Drum roasting entails the beans rotating inside a drum with the flame usually heating the outside of the drum, whereas fluid bed roasting entails a jet of hot air forcing the beans to rise & fall inside a chamber.
At Yarra Coffee, we drum roast our coffee beans in 30kg batches.
As the green coffee beans are roasting, they darken in color becoming yellow, then a light tan or cinnamon color, and eventually a deep rich brown. Part of this color change is the result of sugars within the beans caramelizing, which also contributes to flavor. The beans even make audible popping sounds as moisture escapes. And, oils rise to the surface of the beans making them shine. Coffee beans will retain more of their unique flavor characteristics at lighter or regular roasts. These characteristics are a result of the region in which each bean is grown. The type of soil in a particular region, as well as the weather conditions in that part of the world have a strong effect on an individual coffee’s flavor.
The roasting process reduces the input weight by about 18%, depending on degree of the roast and increases the mass as the beans expand.
Aroma is a very important component in a coffee’s flavor. Since our sense of smell directly relates to our sense of taste, the aroma of a coffee largely impacts how we perceive the flavor of that coffee. The aroma of different coffees can vary greatly. Many of our fine varietal coffees have aromas ranging from fruity or berry like, to nutty, to buttery, and even wine like.
Most of us, in the specialty coffee industry, use aroma as the first indication of a coffees overall quality. And even more importantly, we use aroma to point out any potential faults.
Body is the weight of the coffee that can best be sensed by allowing the coffee to rest on the tongue and by rubbing the tongue against the roof of the mouth. Body ranges from mild, to medium, to full and is a result of the fat content.
Acidity is the bright, sometimes sprightly, taste that adds life to a coffee. It is likened to the dry but bright sensation experienced on the backside of your tongue. Perceived acidity does not necessarily correlate to the pH level of a coffee, but is believed to be the result of the acids present in coffee.