In coffee, the term 'strength' is used to refer to different things. Sometimes it refers to the intensity of flavour of a coffee.
Other times it refers to a coffee’s weight or texture, and whether it feels ‘heavy’ or ‘watery’, for example.
It also refers to the concentration of dissolved coffee flavour within a final brew, and this last definition is the one we’ll use for the purposes of this post.
Strength, as in the concentration of dissolved coffee flavour within a brew, impacts the taste of an espresso in that too low a concentration can prove thin or watery, while too high a concentration may prove heavy or tar-like, which can overwhelm the palate.
When it comes to espresso, getting the ideal balance of strength, mouthfeel (or texture) and intensity of flavour takes time, and it’s really more of a moving target than a hard-and-fast formula.
But this test and learn aspect is all part of the fun and challenge of making espresso and, if you approach it with patience, it can be pretty rewarding.
And remember, everyone has a slightly different idea of what the perfect espresso should taste like, so it’s well worth playing around with the parameters until you find your own idea of perfection.
The Strength of an Espresso
Put simply, the strength of a coffee is the percentage of the total brew that is made up of coffee itself.
A typical espresso shot sits somewhere between 7 and 12% strength, with the remaining 88 to 93% being water.
This might not sound like a lot, especially when you think about how punchy an espresso shot can taste, but then coffee is one of the most intense flavouring agents around — the slightest increase or decrease in strength is easily registered by our taste buds, whether you’re a beginner or a sensory pro.
As the maker of an espresso, you can determine the level of strength by adjusting certain variables – like the amount of coffee used (the ‘dose’); how coarse or fine that coffee is ground (the ‘grind size’); and the amount of time the coffee is extracted for (‘extraction time’ or ‘brew time’) .
Temperature also plays an important part, but it’s generally controlled by the machine and should remain fairly stable.
All of this matters, because the strength of a shot directly affects the other two elements that we touched upon above: the intensity of flavour experienced, and the weight, texture and mouthfeel of the coffee.
For example, too low a dose of coffee will give you a weak-tasting or watery espresso, while too high a dose of coffee could give you a heavy, overly viscous espresso.
How Origin Affects Flavour
The flavour of any coffee, on the other hand, is something that is established before the beans ever reach a barista or home brewer. In fact, a great deal of a coffee’s flavour is established before it even reaches a roaster, while it’s being grown and processed as green coffee at origin.
Naturally processed green coffee
For a more complete exploration of the factors that determine coffee flavour at origin, you might want to read our posts on coffee roasting, single origin coffee and coffee processing. But to summarise, these are the key factors:
Where coffee is grown
Where the coffee was grown, because altitude, temperature, humidity, rainfall and soil composition vary significantly from country to country and region to region.
All of these factors influence how the plant and cherries grow, and the resulting flavours in your cup.
The type of coffee species
The species (usually Arabica or Robusta – there are actually loads of species (124), it's just these are by far the most common.) and variety of the coffee (you may have heard of Bourbon, Heirloom, Caturra, Gesha and many others) will affect the conditions that it can grow under.
While in isolation, these differences won’t determine the flavour, they will interact with the growing environment to influence the end result.
How the coffee is processed
Washed coffee being dried
How the coffee is processed – whether it’s washed, natural, or honey (or a newer, more experimental method).
Washed coffees tend to be cleaner, lighter bodied, and higher in acidity; natural coffees sweeter, less acidic and full bodied; and honey processed coffees somewhere in between.
How Roasting Affects Flavour
Checking the colour of beans mid roast
When we talk about all of these factors at origin affecting flavour, we’re talking about the flavour of the coffee once it’s been roasted.
Green coffee is pretty flavourless as a brewed drink and it’s only through the roast that these flavours are unlocked and revealed.
How a coffee is roasted is often called its roast style, or roast profile.
Many coffees, and particularly those found in a supermarket, categorise their roast styles in terms of strength to simplify it for coffee shoppers, often with a number rating.
This is another reason why understanding strength in coffee can be so confusing, and ‘strength’ described here relates to the extent to which the beans have been roasted, with lighter roasts labelled ‘weaker’, and darker roasts labelled ‘stronger’.
It has nothing to do with caffeine content, which is a common mistake.
A less confusing, and more useful way of looking at coffee roasting is to think about light, medium and dark roasts, and the various increments in between.
Just as coffees grown in different countries and regions will develop unique flavour profiles as a result of their growing and processing conditions, we believe each coffee should be treated individually in the roast, to emphasise the best bits.
While one coffee might be suited to a light roast to complement its delicate citrus fruit and floral flavours, another may need a light-medium or medium roast to bring out it’s natural sweetness and heavier body.
Generally speaking, though, this is how roast level tends to affect a coffee:
Light Roasted Coffee
When ground, a good quality light roasted coffee will be aromatic on the nose. When brewed, it will have a relatively high acidity and sweetness, a low bitterness. The body will be on the lighter, more delicate side.
Medium roasted coffee
Medium roasted coffee beans will still produce a punchy aroma when ground, but in the cup you’ll get a heavier body, a more subtle acidity, and a richer sweetness. There will be some bitterness, but not a lot.
Dark roasted coffee
Although we personally wouldn’t roast anything dark, it does have a place. This style of roasting is used widely in many high street chains, and lots of coffee drinkers like it.
Dark roasted coffee beans tend to be smooth and oily in appearance, and when brewed they will be low in both acidity and sweetness but have a heavy body, whereas the bitterness brought about by over-roasting will likely mask any unique flavour characteristics the coffee may have had.
Roasting for Espresso
An often-debated subject is whether coffee should be roasted differently for filter and espresso brewing.
And for us, the answer depends on the type of coffee and how it’s going to be brewed and used.
Beans intended for espresso rather than filter are usually roasted slightly darker, especially if the espresso is being paired with milk.
This is because the lower acidity and extra body will ensure that the flavour is able to blend well with, but still stand out from, that of the milk.
Times and tastes have changed though, and some people (including us) love a juicy, acidic, light roasted espresso as much as a balanced and full bodied one, but arguably the margin for error when dialling in a light roasted shot will be narrower.
Between the flavours that are established at origin and the added influence of roast styles, how should we, as coffee drinkers, talk about flavour?
And how do we get the right balance of strength and flavour when making espresso?
There are different ways of talking about flavour in coffee depending on the situation and the coffee in question.
A barista serving a single origin espresso in a specialty coffee shop might choose to focus on the notes and characteristics that developed at origin, whereas a traditional Italian-style espresso on sale in a supermarket is more likely to be defined by characteristics that developed during roasting.
Below is a list of common ways of describing a coffee’s flavour which will hopefully sound familiar.
- Bold and Full-Bodied
- Bold and Rich
- Chocolatey and Nutty
- Fruity and Bright
- Light and Floral
- Smooth and Balanced
- Smooth and Mellow
- Strong Italian Roast
With specialty coffee, we tend to talk about flavour in a more detailed and nuanced way – by describing flavours, aromas and characteristics.
There are over 800 known aromas (confusingly, these are specific flavours that you taste with your nose) in Arabica coffee, and the higher the quality of coffee, the clearer these aromas will be to detect.
To get familiar with these flavours and aromas, we’d recommend having a look at the coffee taster’s flavour wheel.
Alongside flavour notes, we also tend to describe specialty coffee in terms of its characteristics - like sweetness, acidity, body, balance and aftertaste. Professional coffee tasters (and some home brewers) sometimes score these qualities in a structured tasting session called a Cupping.
Cupping new coffee samples at the roastery
For a more detailed tips on how to taste, think about and describe coffee, we’d recommend having a look at our post: How to Cup Coffee: A Step By Step Guide
Which Flavours Work for Espresso?
Generally, coffees with a high level of sweetness and body work well in espresso and milk drinks of all sizes.
Looking back at the flavour wheel, we’re talking dominant flavour notes that fall into the nutty / cocoa and sweet brackets, like chocolate, nuts, honey and caramel – all of which complement milk really well.
On the other hand, coffees with flavour notes that fall into the Fruity and Floral flavour brackets – think citrus fruits, berry notes, or elderflower and Jasmine – are best reserved for black coffee, whether that’s an espresso shot or a filter coffee.
Crisp, clean and floral coffees tend to work particularly well when brewed as filter, as their delicate character suits the lighter body created by this method.
Getting the balance right
As we mentioned at the beginning of this guide, getting the right balance of strength and flavour in an espresso takes a bit of practice, but with enough effort and experimentation you should be slinging satisfying shots in no time.
It’s well worth trying out different roast styles and tweaking the recipe you use to extract your espresso until you find a concentration, and a flavour, that you are 100% happy with.
After all, making espresso is supposed to be fun.