Coffee is a beverage made from the liquid extracted from roasted and ground beans (or seeds) from the tropical plant ‘Coffea’.
Although there are countless species of Coffea, the most commonly used are Coffea arabica (Arabica coffee) and Coffea canephora (Robusta coffee).
Arabica coffee is better regarded than Robusta because of its smooth and aromatic qualities. Robusta is more bitter.
Robusta is used as an inexpensive substitute for Arabica in commercial coffee blends for the following reasons:
- Easier to grow: less susceptible to diseases
- Economical: it yields larger crops
- Caffeine content: it contains 40-50% more caffeine than Arabica.
Robusta coffee can be desirable in a blend for its 'body' and better 'crema'.
1- The coffee berries or cherries are picked when ripe, by hand or machine.
2- The cherries are skinned. Depending on the method used, the fruit covering the seed or bean can be removed either before or after the drying process.
3- The coffee beans are dried, sorted by colour, size and density and then graded.
The coffee cherries are now called green coffee beans.
Here's what happens during the roasting process...
After a few minutes, in the first crack stage, the bean 'pops' audibly like popcorn as the moisture dries.
- A chemical reaction called pyrolysis breaks down starches in the bean into sugar.
- The caramelisation of the sugar changes the colour of the bean.
- Caffeol or coffee oil (responsible for the distinct flavour of coffee) is released during the second crack stage.
- The longer the roasting process, the darker and shinier the coffee beans becomes.
- Darker roast's flavour can dominate and eclipse the signature characteristics of coffee regions.
The roasting time varies according to many factors:
- Age, grade, quality and moisture of the coffee beans
- Origin of the bean. Light roast is preferable for keeping the original regional flavours.
- Coffee roast types desired by the Coffee Roaster for his 'recipe' or 'roast profile.
Characteristics of coffee roast types
Each coffee roast type has its own characteristics.
1- Light Roast (also called Cinnamon)
- Roasted to the first crack
- Dry surface
- Lighter-bodied, higher acidity
- No obvious roast flavour
2- Medium Roast
- Roasted a few minutes longer after the first crack
- Dry surface
- Sweeter than light roast, more body and balanced acidity and aroma
3- Full or Dark Roast (also called Italian or Viennese)
- Roasted to the second crack
- Slightly shiny beans
- A bit spicy, heavier body and mount feel
- Roast flavour is evident
4- Double Roast (also called French)
- Roasted a few minutes longer after the second crack
- Very oily surface
- Roast flavour mask the flavours characteristic of the bean's origin.
The Degassing Process
The roasting process causes the coffee beans to release carbon dioxide for several days after roasting. Packaging coffee beans without degassing could cause coffee bags to burst under the pressure of the gases.
To accommodate the degassing process, two ways are used to package coffee.
The roasted coffee beans are left to cool to ‘gas off’' and then vacuum-packed (the air drawn out of the bag). Unfortunately, by the time coffee beans are packaged, they have already been exposed to their worst enemies, moisture, light and oxygen and lost their initial freshness. Vacuum-packaging is used by coffee suppliers who sell long-life shelf coffee. The 'brick' look coffee packs are easy to transport globally and store for many months. Can you really believe the 'fresh coffee beans' labels?
2- One-way valve packaging
The coffee is packaged immediately after roasting, keeping its freshness. With the one-way valve system, degassing occurs when the coffee is in the bag. Carbon dioxide can escape without letting oxygen and moisture in. One-way valve is now industry standard for Australian coffee roasters. You can easily recognise the button-look valve at the top of the package.