Learn
Coffee: from flower to cup
What a coffee bean is, how robusta differs from arabica, how processing and roasting change the taste, and how much caffeine is in a cup — with sources.
The bean’s journey
Eight steps, and at each one the coffee can get better or worse.
- FlowerThe coffee tree flowers with white, fragrant blossoms, usually after the rains. Each flower can become a cherry.
- CherryThe fruit ripens for months, from green to red — in some varieties to yellow. Inside are two seeds: the coffee beans.
- HarvestPicking starts when about 80% of the fruit is ripe. Specialty coffee is picked by hand, ripe cherries only, in several passes: hand picking usually gives better beans.
- ProcessingInside the cherry, under the pulp, are two seeds — the beans. The pulp is washed off with water (washed process), dried together with the bean (natural) or partly left on (honey). This changes the taste.
- Drying and hullingThe beans dry in the sun or in dryers to about 10–12% moisture, then the parchment layer comes off. The result is green coffee — the form coffee travels in.
- ShippingGreen coffee ships in 60 kg bags or in lined containers. It keeps for months, but towards the end of the year after harvest it starts to lose its brightness.
- RoastingIn the roaster the bean heats for 8–15 minutes to about 200–230 °C: it loses over a tenth of its weight, mostly water, browns and cracks. For a few days after roasting it gives off carbon dioxide.
- CupAbout a fifth of the weight of the ground coffee ends up in the cup: an extraction of 18–22% counts as tasty. Grind, water temperature and time decide which fifth it will be.
Arabica, robusta and the rest
Nearly all the world’s coffee comes from two species: arabica and robusta (Coffea canephora). Vietnam is the leading robusta country.
| Arabica | Robusta | Liberica and excelsa | |
|---|---|---|---|
| Latin name | Coffea arabica | Coffea canephora | Coffea liberica (incl. var. dewevrei — excelsa) |
| Share of world output | about 53% of the crop | about 47% of the crop | under 1% |
| Caffeine in the bean | 1.1–1.3% (roasted) | 2.4–2.5% (roasted) | 0.9–1.2% (green) |
| Where it grows | 550–1100 m in the subtropics, 1100–1900 m near the equator | from sea level to 900 m | warm lowlands |
| Taste | acidity, sweetness, aromas | body, bitterness, chocolate, nuts | fruit, smoke, unusual |
| In Vietnam | Lâm Đồng (Đà Lạt), Sơn La, Quảng Trị | Central Highlands: Đắk Lắk, Lâm Đồng, Gia Lai | cà phê mít — since 1908, rare today |
Sources (3)
Robusta is not “bad arabica”
It is a different species with its own taste: more body and bitterness, less acidity, more caffeine. Carefully picked and processed robusta can be very good — it has its own quality standard, Fine Robusta.
Why robusta costs less
It grows lower down, stands up better to disease and heat, and yields more. Most of it goes into instant coffee and espresso blends.
Vietnam’s arabica
About 4% of the harvest, mostly from the Lâm Viên (Langbiang) plateau near Đà Lạt and the mountains of Sơn La in the north. A growing focus for specialty roasters.
Processing: what happens to the cherry
The same variety tastes different after different processing.
Washed
The pulp comes off right away, the remaining mucilage is removed by fermentation and water, and the clean bean is dried. A clean taste, bright acidity.
Natural
The whole cherry is dried, then the dried pulp comes off. A fruity, sweet taste and a fuller body. Most of Vietnam’s robusta is processed this way.
Honey
The skin comes off, part of the sticky pulp stays on the bean, and it dries like that. Between washed and natural: sweet and clean.
Wet-hulled
The parchment comes off while the bean is still wet. Typical of Indonesia: earthy, spicy notes.
Anaerobic fermentation
Cherries or beans ferment without air in sealed tanks. Flavours new to coffee, from winey to tropical; Vietnamese farms work with this too.
Sources (1)
Roasting a single bean
Move the slider or press “Roast”: the bean goes from green to dark in 13 minutes — here, in 12 seconds.
A typical roast
Green bean
The raw bean is hard and smells grassy; moisture is about 10–12%. The taste of coffee only appears in the roaster.
A typical drum-roaster curve, not the profile of a specific batch: every roaster and every bean has its own times and temperatures.
Freshness and storage
Coffee has a date: for green beans it is months, for roasted beans weeks, for ground coffee minutes.
Look for the roast date
Not “best before” but the roast date. For a few days after roasting the beans give off gas — that is why a fresh roast gets a rest. At room temperature whole beans go stale in 4–6 weeks, ground coffee in 2.
IARC Monographs Vol. 116 — Drinking coffee, mate, and very hot beverages · 2018
Keep beans, not grounds
Whole beans in an opaque airtight jar, away from heat, moisture and light. Buy for one or two weeks and grind right before brewing.
National Coffee Association — Storage and shelf life · 03.11.2026
Fridge and freezer
In the fridge beans stay fresh for about two weeks, in the freezer for 3–4 months: in an airtight container, taking out a week’s supply at a time.
National Coffee Association — Storage and shelf life · 03.11.2026
The new crop
Green coffee keeps a long time, but slowly loses sugars and brightness. Vietnam’s robusta is picked from October to January and reaches roasters a few months later.
Selmar et al. — storage of green coffee (Annals of Botany, 2008) · 02.11.2007 · Tạp chí Công Thương — Việt Nam bắt đầu mùa thu hoạch · 08.10.2024
Caffeine and health
Short and with sources. This is not medical advice: in pregnancy, with heart conditions or when taking medication, ask a doctor.
How much is no concern
EFSA: for healthy adults up to 400 mg of caffeine a day and up to 200 mg at a time; in pregnancy and while breastfeeding up to 200 mg a day; children and teenagers up to 3 mg per kg of body weight. 100 mg shortly before bed makes falling asleep take longer for some people.
EFSA — Scientific Opinion on the safety of caffeine · 27.05.2015
Robusta holds twice the caffeine
Roasted arabica holds 1.1–1.3 g of caffeine per 100 g, robusta 2.4–2.5 g. That is why a robusta phin is stronger than the cup suggests.
IARC Monographs Vol. 116 — Drinking coffee, mate, and very hot beverages · 2018
How long it lasts
The half-life of caffeine in healthy adults is about 4 hours, ranging from 2 to 8; in pregnancy 6–16 hours.
EFSA — Scientific Opinion on the safety of caffeine · 27.05.2015
Coffee and cancer
In 2016 IARC moved coffee to Group 3 — “not classifiable as to its carcinogenicity to humans”. Very hot drinks, above 65 °C, went to Group 2A: it is the temperature, not the coffee.
IARC — Press Release No. 244 · 15.06.2016
The filter and cholesterol
Unfiltered coffee — cezve, French press, boiled — carries cafestol and kahweol, which raised LDL cholesterol in studies. A paper filter holds back nearly all of them.
Urgert et al. — cafestol and kahweol in coffee brews (J Agric Food Chem, 1995) · 1995 · Cai et al. — coffee and serum lipids, a meta-analysis (Eur J Clin Nutr, 2012) · 2012
Glossary
- Arabica
- Coffea arabica — the most widespread coffee species: grows higher, brighter acidity, less caffeine.
- Robusta
- Coffea canephora — the second species: more body, bitterness and caffeine. The backbone of Vietnam’s harvest.
- Phin
- The Vietnamese drip filter with a press and a lid.
- Specialty
- Coffee that scores 80 points or more under the SCA cupping protocol. Since 2024 the SCA has been moving to a new assessment, the CVA.
- Fine Robusta
- The quality standard for robusta: the same idea — 80 points or more.
- Cupping
- A tasting by protocol: coffee is brewed in cups, the crust is broken, and the coffee is tasted from a spoon.
- Extraction
- The share of the ground coffee that dissolves in the water. Around 18–22% tastes good.
- Ratio
- How much water per gram of coffee: 1:16 means 16 g of water to 1 g of coffee.
- Bloom
- The first seconds of brewing: the coffee is wetted, releases gas and rises.
- Crack
- The sound of beans cracking in the roaster: the first marks the start of a light roast, the second of a dark one.
- Fermentation
- The fermenting of pulp and bean during processing; producers steer it for flavour.
- Lot
- A batch of coffee from one farm or station, one process and one harvest.
- Ristretto and lungo
- Espresso with a smaller and a larger yield from the same dose.
- Crema
- The foam on espresso: gas and oils pushed out by pressure.
- Tây Nguyên
- Vietnam’s Central Highlands — the country’s main coffee region.
- New crop
- Green coffee from the latest harvest; last year’s is called old crop.