Espresso is a tiny cup of coffee that packs a big punch and that little bit of liquid will certainly wake you up. But why is it so strong?
Espresso is a brewing method that creates a very intense tasting, thick liquid that’s served in small cups. The reason for this strength is that a lot of grounds are extracted into a small amount of water. This is done by using a lot of grounds, grinding them very fine and extracting them under pressure.
Let’s look at the different factors and how they influence the strength of espresso.
Why is espresso so strong?
Espresso is one of the strongest types of coffee you can find. But why is it so strong? We’re talking about taste here but the reasons why espresso is high in caffeine are the same as for why the taste is strong.
There are three main reasons why espresso tastes so strong:
- Fine grind size
- High Pressure
- Dark Roast
It can all be summarized as very fast and efficient extraction. Much faster and more efficient as other brewing methods like pour over.
Let’s take a look at those factors in detail.
The first reason espresso is so strong is that it uses a lot of coffee grounds for the amount of liquid that ends up in your cup. A single shot of espresso is about 28 grams of liquid but about 14 grams of coffee grounds is used to brew this. That is a 1:2 ratio (one gram grounds for every two grams in the cup). For reference, pour over coffee uses a ratio around 1:15.
That alone means there is much more coffee grounds available for every milliliter of water than for a pour over. You probably have noticed that pour over or drip coffee is much more diluted compared to espresso.
The strength of coffee is mostly decided by how much of the coffee bean you get into the water. If you can get more into less water, it’s stronger.
Also, the amount of caffeine you get in a cup is largely decided by the amount of coffee you use. Caffeine is very easily soluble in water so pretty much any contact with water will extract the caffeine. So even if not all the taste of coffee is there, you’ll probably still have a lot of caffeine in espresso.
#2 Fine grind
However, because you have so much coffee grounds for so little water and you want to extract that coffee in a short amount of time (about 25-30 seconds), you need to make the extraction very efficient and quick.
A pour over takes about three minutes while pulling a shot of espresso only takes about 30 seconds. That means the water gets more time to hang out with the grounds with a pour over and therefore more chances to extract the grounds. However, for pour over and most other brewing methods the grounds are much coarser than for espresso.
The espresso grounds are much finer than for pour over. That means there is more surface area for the same amount of coffee grounds. More water can interact with the grounds at the same time which means the extraction is much faster and can be done with less water. If you put more of the coffee bean in less water, it will be much stronger.
To help extract all of the coffee grounds in such a short time with little water, you’re going to need a little more than just a fine grind. Pressure is what makes espresso the strong, intense and thick drink you know and love.
Espresso is brewed by pushing hot water through the coffee bed at about 8-9 bar of pressure. This pressure pushes helps the water penetrate the coffee grounds much faster and squeeze the coffee out of the filter. The pressure also helps speed up the extraction through other ways.
#4 Dark roast
While over the last years, things have been changing, traditionally espresso has been brewed with a dark roasted coffee. That dark roast does two things:
Roughly speaking, the darker a coffee bean is roasted, the more bitter notes come out. While the bitterness is not a good indicator of overall strength, the bitterness is what most people associate with strength. However, caffeine is one of the first things to dissolve in the brew water and the very bitter notes come later so they aren’t really related.
The second reason is that darkly roasted beans are easier to extract. Darker roasted beans are drier and more porous making extraction easier. Dark roasted beans also break up easier so grinding them will result in more coffee dust known as ‘fines’. Those are very small particles that therefore are very easy to extract but also cause bitterness.
So you might notice that all the things above have to do with extraction. To really understand why espresso is so strong, it’s good to understand extraction.
Coffee beans are made up of materials that are soluble in water and materials that are not. We want a lot (but not all) of the water soluble in our cup of coffee while keeping out the insoluble parts. The soluble parts in the water is what makes coffee coffee. The insoluble materials just show up like residue or sludge in your cup which you don’t want.
You don’t want to extract all the soluble material either. The trick of brewing coffee is to get the right amount of solubles out of the coffee bean while not overdoing it and keeping the grounds out of your coffee cup. The amount of solubles you get from the coffee grounds is called extraction.
So to get the right extraction, an amount of work has to be done. This work is done by the water. You want to get the soluble materials and water is the solvent. If you see the coffee grounds as a gold mine, the water is the miner. The miner takes the materials you want into your cup. If you want more from your gold mine, you’ll either need more miners or one miner to work more efficiently.
Getting back to coffee, you either need more water or make the water extract the grounds more efficiently through higher temperature, smaller grind size and higher pressure.
Higher extraction isn’t always better though. In general, if you over extract, you went too far and the coffee will taste very bitter. Under extract and you’ll get very sour, acidic coffee. Because all the soluble compounds are dissolved at different rates, some compounds are extracted earlier and easier than others. And the compounds that make coffee sour are usually released first and the very bitter ones last.
Getting the correct balance of extraction is the key to good tasting coffee. While there are methods of measuring the exact extraction, they are out of reach for most people and not really important. In the end it’s about the taste. If you like the taste of your brew, that’s all that matters. Understanding extraction just helps you give the knowledge to improve your coffee.
Why is espresso extracted so fast?
For pour over coffee, you just send more miners (water) into the mine to get everything. However, with espresso, you only have a single miner that has to do everything by himself. So what can you do make him work harder? How can an espresso machine extract so much from the coffee in such a short time and with so little water?
The key is pressure and grind size:
A small grind size means that the same coffee bean is broken up into smaller pieces. That means there is much more surface area for a given amount of coffee. The more surface area there is, the more water can touch and interact with the same weight of grounds at the same time. This means extraction can be done much faster. It’s like being able to send more miners into your gold mine.
The other part is the pressure. This pressure helps push the water into the coffee grounds and through it. This helps penetrate the coffee grounds faster and squeezing it out on the other end into your cup. Just like squeezing your sponge will get out more soap than just rinsing it. Combine this with the fine grind and you can extract a lot with little water and in little time.
Favorite Espresso Tools
Besides an espresso machine, there are a few other tools that can make your espresso better. Here are my favorites:
- Tamper: A nice tamper helps you tamp your grounds in the filter for the best result. Any correctly sized tamper can do the job but a nice heavy one just feels so much better in your hand than a plastic model. This Luxhaus one (Amazon) has a nice trick up it’s sleeve to make tamping very consistent.
- Beans: Good espresso starts with good beans. Using fresh beans is a big improvement over pre-ground coffee.
- Scales: Getting consistently good espresso means you have to know how much grounds is going into the machine and how much is coming out and how long this takes. A coffee scale is going to make your espresso much more consistent and also makes adjustments a lot easier. The Apexstone coffee scale (Amazon) is cheap and doesn’t look too sleek but is just as accurate as more expensive scales. The TimeMore scales (Amazon) look and feel a lot nicer but cost a bit more.
- Grinder: To make the best of your fresh beans, a good grinder is necessary. Espresso requires a good grinder to get the best results. The Baratza Sette 30 (Amazon) is a good espresso grinder that can also be used for other brewing methods and while not cheap, is good value for money. If you prefer hand grinders, the 1ZPresso JX-PRO is one of the best options (Amazon)
- Distribution tool: After grinding you can get some clumps in the coffee grounds. Those clumps should be broken up so the water can extract all the coffee grounds equally. Distribution tools are very simple things but this one (Amazon) is beautifully made and will look good in your kitchen.