Espresso: Definition, Numbers, and What Actually Matters
Espresso is the smallest portion of coffee with the biggest impact – and at the same time the drink that attracts the most nonsense. That the crema reveals the quality. That it has particularly high caffeine. That there's exactly one correct way to prepare it. This article sorts out what's provable and what isn't.
And because that's part of who we are: there's no espresso police. The numbers below are orientation, not a verdict. If your espresso tastes better longer, shorter, or with sugar, that's your right cup.
What is an espresso?
An espresso is a short, concentrated coffee in which hot water is pressed through finely ground coffee at high pressure. Around 25 to 35 millilitres end up in the cup, topped by a hazelnut-brown layer of foam, the crema. The decisive difference from filter coffee isn't the bean, but the pressure – and the short contact time that results from it.
The name doesn't come from "fast", but from "expressly": the first machines around 1900 brewed the coffee expressly for the customer, that is specifically for the individual order, instead of in large batches for stock. That was exactly the revolution.
What figures define an espresso?
There's no internationally binding standard. What exists is the definition from the Istituto Nazionale Espresso Italiano, which describes its certified Espresso Italiano with five values: 7 grams of ground coffee, 88 degrees water temperature, 9 bar pressure, 25 seconds shot time, and 25 millilitres in the cup – each with a tolerance.
The certified Espresso Italiano
These values describe the Italian bar espresso, not the only possible one. In the specialty scene, noticeably more coffee is often used – 16 to 18 grams in a double basket is the norm today – and the ratio of dose to beverage is deliberately controlled. How we do this at the Coffee Coaching Club is in our article on espresso dial-in.
The 25 seconds are the most-quoted and most misunderstood value. They're an observed figure from Italian bar practice, not a target – and anyone chasing them ends up adjusting the grind size instead of paying attention to taste.
What is the crema – and does it say anything about quality?
Crema is a foam made of emulsified coffee oils and carbon dioxide. CO₂ forms during roasting and stays bound inside the bean; under the 9 bar of the group head it dissolves into the water and bubbles back out again in the cup as the pressure drops. What you see is, at its core, gas in oil.
And now the part you rarely hear: Crema is not a reliable indicator of quality. Above all, it says something about freshness and bean type. Canephora, commonly known as Robusta, naturally produces more and more stable crema than Arabica – so an espresso with a thick crema can simply contain more Canephora in the cup. Pressurized baskets also produce crema virtually at the push of a button, regardless of how the coffee tastes.
Conversely: a very fresh, light-roasted Arabica can have a thin crema that collapses quickly and still taste excellent. Judge your espresso by mouth, not by eye.
How much caffeine is in an espresso?
Noticeably less than most people assume. A shot of espresso of around 30 millilitres contains about 65 milligrams of caffeine, an ordinary cup of filter coffee with 240 millilitres around 95 milligrams. Per millilitre, espresso is clearly the stronger of the two – per portion, filter coffee comes out ahead, because the cup is eight times bigger.
Caffeine per portion, not per millilitre
Two more things additionally influence the value: the bean type and the quantity. Canephora contains roughly twice as much caffeine as Arabica, and a double shot with an 18-gram dose naturally delivers more than an Italian single with 7 grams. The figures given are averages, not a measurement of your cup.
What's the difference between ristretto, espresso, and lungo?
Only one thing: how much beverage you let run from the same dose. The Ristretto is stopped at roughly the same weight as the dose, the espresso at double, the lungo at triple or more. Grind size, bean, and machine stay the same.
Ristretto, Espresso, Lungo
Important here: a lungo is not an espresso lengthened with hot water – that would be an Americano. With a lungo, more water actually runs through the same coffee bed, and that's exactly why it often tastes more bitter: the compounds dissolved last are the unpleasant ones.
Where does espresso come from?
From Italy, but step by step. In 1884, Angelo Moriondo patented a machine that forced steam through ground coffee – though for large quantities at once. In 1901, Luigi Bezzera filed a patent for a machine that brewed individual portions via portafilters. Desiderio Pavoni bought the patents and, starting in 1905, sold the first commercial espresso machines.
These early machines worked with steam pressure and produced a bitter coffee without crema. The breakthrough came in 1947 with Achille Gaggia: his lever machine used a spring-loaded piston to press the water through the ground coffee at around 12 atmospheres – and in doing so, produced for the first time the foam Gaggia would come to call crema caffè from then on. The espresso we know today is therefore younger than the car.
Which bean is suited for espresso?
Basically any of them. "Espresso beans" aren't a separate plant, but a roasting decision: roasted a bit longer and darker than filter coffee, so the aromas dissolve well under pressure and in a short time, and the acidity recedes. The same bean can taste fruity as a filter roast and chocolatey as an espresso roast.
Classic Italian blends often contain a share of Canephora – for crema, body, and a robust, earthy base note. Pure Arabica roasts, on the other hand, tend to be clearer and sweeter, often with more acidity. Both are legitimate. Find our selection among the coffee beans, and what "specialty" means in this context is covered in the article on Specialty Coffee.
What does a good espresso taste like?
However it tastes good to you – but a few characteristics can be described independently of taste. A well-made espresso is dense but not syrupy-thick, has sweetness, and stays pleasant in the mouth after swallowing. What it shouldn't be: sharply sour, harshly bitter, or thin and watery.
| What you taste | Likely cause | First step |
|---|---|---|
| Sour, thin, salty | under-extracted | grind finer |
| Bitter, dry, harsh | over-extracted | grind coarser or run it shorter |
| Bitter and thin at the same time | channeling in the coffee bed | check your puck prep, not the grind size |
| Flat, without sweetness | bean too old or too fresh | check the roast date |
Why does your espresso taste different at home than at the bar?
Because at the bar, three things come together that are usually missing at home: a grinder dialled in on the same bean all day, a machine with stable temperature, and a person who pulls twenty shots a day instead of one. None of it is magic, but all of it is routine.
The single biggest lever at home is the grinder. A good machine with a mediocre grinder delivers less than a mediocre machine with a good grinder. The second lever is a scale – not because grams taste better, but because it lets you repeat what worked.
Frequently asked questions about espresso
How much caffeine does an espresso have?
A portion of around 30 millilitres contains, on average, about 65 milligrams of caffeine. An ordinary cup of filter coffee with 240 millilitres comes to around 95 milligrams. Per millilitre, espresso is stronger in caffeine; per portion, it contains less.
How much espresso is 25 ml?
About one big sip – the classic Italian portion made from 7 grams of ground coffee. In the specialty scene, the double shot is the norm: 16 to 18 grams of dose yield, depending on the recipe, around 30 to 40 grams of beverage.
Is a thick crema a sign of quality?
No. Crema mainly says something about freshness and bean type: Canephora produces more crema than Arabica, and pressurized baskets produce it regardless of coffee quality. An outstanding light-roast Arabica can have a thin crema.
What's the difference between espresso and lungo?
With a lungo, more water runs through the same amount of ground coffee, usually around triple the dose instead of double. This makes the cup bigger and lighter, but often also more bitter, because mostly unpleasant compounds dissolve last.
What's the difference between espresso and Americano?
With an Americano, a finished espresso is diluted with hot water. With a lungo, the extra water runs through the coffee bed. Same cup size, completely different taste – the Americano stays closer to espresso in flavor.
Does espresso need special beans?
No, but a suitable roast helps. Espresso roasts are roasted a bit longer and darker, so the aromas dissolve well under pressure during the short brew time and the acidity recedes. Light filter roasts can be prepared as espresso, but demand more fine-tuning.
Why does my espresso taste sour?
Usually it's under-extracted: the grind is too coarse, or too little beverage runs into the cup. Grind one step finer and don't change anything else. That said, not every acidity is a flaw – light roasts naturally bring fruity acidity with them.
And now?
If you want to fine-tune your espresso, the next step is the Dial-in – there you'll find how we match grind size and dose to each other. If you'd rather continue with milk, you'll find the sequel with the Cappuccino and the Flat White.
And if you'd rather go through it together at the machine: in our showrooms in Bern and Zürich, that's exactly what we do – in the Workshops or the Barista course in Zürich. There's no espresso police. In the end, all that matters is whether you like the cup. United by Coffee.
Sources
- Istituto Nazionale Espresso Italiano: L'Espresso Italiano Certificato – key figures 7 g, 88 °C, 9 bar, 25 s, 25 ml.
- On the history (Moriondo 1884, Bezzera 1901, Pavoni from 1905, Gaggia 1947) and on caffeine content as well as the composition of crema: compiled in the article Espresso, English Wikipedia, with the sources cited there.
