The first article in this series on coffee covered its early roots and routes. Coffee has planted itself all over the globe from the forests of Africa to the Middle East, the Indian Ocean Islands, South and Southeast Asia and the tropical Americas. Nearly all the commercial coffee varieties (97%) that grow globally are derived from either Coffea arabica or Coffea robusta. But how do different coffee varieties emerge? What are some of the favored varieties? Before the green beans are roasted, what are the factors that affect quality? How can someone roast coffee beans at home?
AFRICAN ORIGINS OF COFFEE
A three-part series:
Definitions and progression:
» Caramelization occurs when sugars in a compound are heated, release water, brown and produce new flavor compounds. It usually occurs at temperatures up to the first crack of coffee roasting.
» First crack produces caramel-like notes.
» Maillard reaction occurs when a sugar and a protein interact when heated to produce browning and a range of different flavor compounds. The Maillard Reaction takes place slowly at room temperature, at higher temperatures and proceeds quickly during and after the first crack.
» Second crack produces smoky woody asphalt-like notes.
What are some of the salient characteristics differentiating Arabica and Robusta?
- Superior taste
- More susceptible to pests and disease
- Slightly larger beans
- Higher fat and sugar content than Robusta
- Best for all types of roasts
- Self-pollinating, which results in less genetic diversity and less variability
- Inferior taste
- Less susceptible to pests and disease
- Smaller beans
- Higher caffeine (double) and chlorogenic acid (CGA) content
- Best for dark roasts and espresso
- Cross pollination, which results in more healthy plants
How plant varieties emerge
from soil to soil
From Arabica emerged two well-known varieties, C. arabica var. arabica (typica) and C. arabica var. bourbon. According to genetic researchers, historical data indicate that Typica originated most probably from a single plant from Indonesia that was subsequently cultivated in the Amsterdam botanical gardens in the early 18th century. The Bourbon genetic base originated from coffee trees introduced from Mocha (Yemen) to the Bourbon Island (now Réunion) in the early 1700s.
When a plant migrates and grows in a new location, it adapts if it can. The migration may be around the corner to a sunnier side of the slope or as far away as another continent. The first coffee plantation on the Bourbon Island (Réunion), for example, yearned for the soil it first grew in — yes, I am attributing human qualities to a plant, but stay with me. Coffea arabica said — and certainly not with an ancient Latin accent but more like a Kafa accent with a tinge of Yemeni Arabic and the sailor slang of the Mocha Port — “Where am I, this soil is too sandy, and this sun’s heat is a bit much for my forest montane constitution and the salt in the air. Ya Allah, enough with the salt! And why do the minerals in the soil taste so nasty? And, hold on, what the hell is that fungus creeping on my leaves!” Get my point?
So the coffee cherries that survived got replanted. The second generation adapted. A unique tasting coffee bean emerged unlike its ancestors from distant Yemen or Ethiopia. This generation’s crop, now firmly identified as Island coffee, possibly contained more sugar, less of a particular protein or a different concentration of minerals. When the ultimate alchemical roasting occurred, new flavor compounds surfaced, and the world got Coffea arabica var. bourbon. That is one story of a coffee plant. Manifold factors determined taste. On the one hand, a brilliant creation of a new coffee variety materialized, on the other, the diminution of genetic diversity ensued. Wonderful and catastrophic, all at the same time.
Dry, wet and natural pulp-drying processes
Ripe coffee beans are processed in one of three ways.
Dry process is the original method that uses less machinery. Dried directly in the sun, the green seed is torn out of the dried dark fruit. This process can result in including unripe beans. And it requires more labor to hand pick the defects and contaminants.
Wet process entails removing the fruit, then washing it in water so unripe beans, defects and contaminants float to the top. The beans are fermented to remove the final mucilage fruit layer surrounding the bean and then dried.
Pulp natural process is a hybrid of the wet and dry. The fermentation process of the wet process is skipped and instead, the beans dry with some fruit still attached. This newest technique produces a cup that is less acidic and more full-bodied and is a cleaner process. It has been dubbed the “miel” or honey process in Costa Rica. (Sweet Maria’s is an excellent source for information on all aspects of green coffee beans.)
What to look for in a green coffee bean?
To assess a quality batch of green beans, look for uniform shape, color, size and evenness. These characteristics allow for even roasting of the beans. This ensures a consistent and defined taste.
Top photo: Green coffee beans. Credit: Sarah Khan
This article was partially underwritten by the The Christensen Fund, a nonprofit organization, dedicated to biocultural and agricultural diversity of marginalized people and landscapes globally.