Step 1 · Roast

Roast levels and processing: where coffee's flavor comes from

Updated November 2026 · 4 min read

Two decisions made long before you brew shape most of what's in your cup: how the coffee was processed after harvest, and how dark it was roasted. Here's what each one does, and how to brew with it in mind.

What roasting does

Green coffee is a dense, grassy-smelling seed. It's hard to grind and tastes nothing like coffee. Roasting transforms it in a few minutes of intense heat, usually 9–15 minutes in a commercial roaster. The roast moves through a few stages:

• Drying. Moisture cooks off and the beans turn from green to pale yellow. The smell is grassy, then like hay or bread.
• Browning. Maillard reactions between sugars and amino acids create hundreds of aroma compounds, and the beans turn tan, then light brown.
• First crack, at around 196°C. Steam and gas build up inside the bean until it audibly pops, a bit like popcorn. The bean expands and becomes brittle enough to grind. Roasts dropped shortly after this are light roasts.
• Development. Sugars caramelise, acidity falls, and bitterness and body build. Every extra minute trades fruit and acidity for sweetness and roastiness.
• Second crack, at around 224°C. The bean's structure starts to break down and oils rise to the surface. From here on you're into dark roast.

Along the way the beans lose roughly 12–20% of their weight, mostly water, and grow by up to half again in size.

Light, medium and dark

There's no industry-wide scale, so one roaster's "medium" can be another's "light". These are the broad families:

About caffeine: dark roasts aren't meaningfully "stronger". Caffeine survives roasting well, and the differences between roast levels are small. Brew strength (how much coffee you use) matters far more.

Processing: what happens before roasting

Coffee beans are the seeds of a fruit, the coffee cherry. After harvest, the fruit has to be removed and the seeds dried, and the way that's done, called processing, has a big effect on flavor. Look for it on the bag next to the origin.

Washed (wet process)

The skin and pulp are stripped off, then the seeds sit in water tanks while fermentation loosens the sticky layer of fruit (mucilage). They're washed clean and dried. Flavor: clean, crisp and bright, with clear acidity. Washed coffees let the variety and growing region come through most clearly.

Natural (dry process)

The whole cherry is dried in the sun, on patios or raised beds, for several weeks, with the seed inside, and the dried fruit is removed afterwards. Flavor: fruity and sweet, often berry, wine-like or tropical, with a heavier body. Naturals can be spectacular, and occasionally funky or fermented-tasting if drying wasn't carefully managed.

Honey (pulped natural)

The skin is removed but some or all of the sticky mucilage is left on while the seeds dry. There's no actual honey; the name comes from the stickiness. Producers label it yellow, red or black honey depending on how much mucilage is left and how slowly it dries. Flavor: between washed and natural: sweet and rounded, with gentler fruit.

Anaerobic and carbonic maceration

Cherries or seeds are fermented in sealed tanks without oxygen, often with careful temperature and time control, before drying. Carbonic maceration, a technique borrowed from winemaking, flushes the tank with carbon dioxide. Flavor: intense and unusual: tropical fruit, cinnamon, boozy or yogurt-like notes. These coffees are exciting to some drinkers and too much for others.

Wet-hulled

Common in Indonesia, especially Sumatra. The outer parchment is removed while the beans are still quite wet, and they finish drying afterwards. Flavor: earthy, herbal and spicy, with a heavy body and low acidity.

Co-fermented and infused

Some producers add fruit, spices or yeast during fermentation. The results can taste like cinnamon or strawberry. Good roasters label these clearly as infused or co-fermented, because the flavors come from the additions rather than the coffee itself.

Origin and variety

Where and how the coffee was grown matters too: altitude, climate, soil and the plant variety. These are broad tendencies, not rules, and processing can shift any of them:

• Ethiopia: often floral and citrusy (jasmine, bergamot, lemon), with berry notes when naturally processed.
• Kenya: often bright and juicy, with blackcurrant, tomato and grapefruit notes.
• Colombia: often balanced, with caramel, red fruit and medium body.
• Brazil: often nutty and chocolatey, with low acidity. A common base for espresso blends.
• Central America (Guatemala, Costa Rica, Honduras): often sweet and clean, with cocoa, stone fruit and gentle acidity.

Brewing each roast

Pour-over tends to reward light and medium roasts, because its clean, paper-filtered cup shows off the fruit and sweetness those roasts keep.

Freshness and storage

• Look for a roast date, not just a best-before date.
• Let it rest. Very fresh coffee is full of CO₂, which makes brews bubbly and uneven. Most coffee is at its best from about 4–7 days after roasting for medium roasts, and 1–3 weeks for light roasts.
• Use it within about a month of opening. It won't go off, but aroma fades steadily.
• Store it airtight, cool and dark. Not in the fridge, where it picks up moisture and smells. For long storage, freezing in small sealed portions works well. Grind straight from frozen.
• Buy whole beans and grind just before brewing. Ground coffee loses aroma within minutes.

How to read a coffee bag

A good specialty coffee bag tells you most of what's above:

• Origin: country, often region, and sometimes the farm or washing station.
• Process: washed, natural, honey, anaerobic and so on.
• Variety: for example Bourbon, Typica, Gesha or SL28.
• Roast date and roast level, or "for filter" vs "for espresso".
• Tasting notes: flavors the coffee reminds the roaster of. Nothing is added; they're descriptions, like wine notes.