It all starts with green coffee
Coffee beans are the seeds of the coffee cherry. Before roasting, they’re green, dense, and smell vegetal - nothing like the coffee you know. They can be stored for months or even years without significant flavour degradation, unlike roasted beans.
Specialty roasters source green coffee directly from farms or through importers who pay above-market prices. The quality of the green bean sets a ceiling on how good the final cup can be - no amount of roasting skill can turn poor raw material into great coffee.
The stages of a roast
Roasting happens in a drum roaster (or air roaster) over 8 - 15 minutes. As temperature climbs, the bean passes through distinct physical and chemical stages:
Drying Phase
~160°C / 320°F
Moisture inside the bean evaporates. The bean turns from green to yellow, and smells like hay or fresh bread.
Maillard Reaction
~160 - 200°C
Sugars and amino acids react to form hundreds of flavour compounds. This is where most of the complexity in coffee is created - similar to what happens when you brown meat or toast bread.
First Crack
~196 - 205°C
Pressure builds and the bean physically cracks open with an audible pop. At this point, you have a light roast. Stopping here preserves the most origin character.
Development Phase
Post first crack
The roaster controls exactly how long to develop after first crack. Longer development = more body, more sweetness, less brightness.
Second Crack
~224°C / 435°F
The cellular structure breaks down. Oils migrate to the surface. This is where dark roast begins - smoky, bittersweet, lower acidity.
What roast levels actually mean
There are no industry standards for what “light,” “medium,” or “dark” mean on a bag. One roaster’s medium is another’s dark. However, the general principle holds:
Light Roast
Stopped shortly after first crack. Highest acidity, most complex origin flavours, lighter body. Best appreciated as filter coffee.
Fruity · Floral · Bright · Tea-like
Medium Roast
Developed longer after first crack. Balanced sweetness, medium body, approachable for most palates.
Balanced · Caramel · Chocolate · Smooth
Dark Roast
Taken to or past second crack. Roast flavour dominates. Lower acidity, heavier body, oily surface.
Bold · Smoky · Bitter · Full-bodied
Specialty roasting vs. commercial roasting
Not all roasting is created equal. Most supermarket coffee is roasted on industrial drum roasters in large batches, prioritising consistency and shelf life over flavour. Beans are often roasted dark specifically to mask defects in low-quality green coffee.
Specialty roasters operate differently. They start with high-quality green beans - typically scoring 80+ on the Specialty Coffee Association scale - and roast in small batches with a clear goal: to express the unique character of that specific lot.
How to read a specialty coffee bag
A well-labelled specialty coffee bag tells a story. Once you know what to look for, you can decode what a coffee will taste like before you even open it.
The single most important number on the bag. Tells you how fresh the coffee is. Peak flavour window is 7 - 28 days post-roast.
Country and often specific region or farm. Ethiopia vs. Colombia vs. Sumatra will taste dramatically different.
Washed, natural, or honey. Washed = clean and bright. Natural = fruity and sweet. Honey = somewhere between.
The cultivar of the plant (e.g. Gesha, Bourbon, Typica). Different varieties have different flavour potentials, like grape varieties in wine.
The roaster's flavour descriptors - e.g. "blackcurrant, brown sugar, juicy." A guide, not a guarantee, but useful when exploring new origins.
Higher altitude = slower growth = denser bean = more complex flavour. Look for 1800m+ for high-quality lots.
Why roast date matters more than expiry date
After roasting, coffee off-gases CO₂ rapidly and starts losing volatile aromatics. The “best before” dates on most supermarket coffee are often 12 - 18 months away - that’s a shelf-life date, not a freshness date.
Specialty coffee is at its peak 7 - 28 days post-roast. After 6 weeks, most of the interesting flavour has gone flat. Always look for a bag with a roast date printed on it - not just a best-before.
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