One of the fundamental variables of brewing espresso is ratio- but what exactly is it and how does it affect how your espresso tastes? How can you use it to make better espresso at home?
Ratio in espresso means measuring the weight of the ground coffee that goes into your portafilter against the weight of the finished espresso in your cup. Changing the ratio will affect the taste and mouthfeel of your shot.
Why measure by weight instead of volume in espresso?
Just like baking: accuracy! The density of flour changes depending on whether you scoop or sift- which can be the difference between a flaky or leaden pastry. To achieve the same results every time, bakers weigh out their ingredients (grams) instead of using volume (cups) so they know exactly what's going into that pie crust.
Until recently (the early to mid 2000s), baristas did use volume to measure out their shots. The traditional "double" was 14g of coffee yielding 60ml (2 oz) of liquid in 25-35 seconds, but doing that didn't get consistent results- and one of the goals is consistency. As it turns out, volume isn’t a reliable unit of measurement because of crema.
During the process of roasting, coffee beans undergo multiple chemical reactions, including the development of gases like carbon dioxide (CO2) inside the bean. Crema, that lovely layer of foam, is the result of CO2 being released as water goes through the coffee bed.
Freshly roasted beans contain a lot of CO2, which means that a 2-ounce shot from coffee roasted 2 days ago could be half crema. Wait another four days, when more of the carbon dioxide dissipates, and what looks like the same 2 ounce shot is now a lot more coffee and a lot less foam- and tastes different. CO2 can affect your shot in other ways, but that's for another day.
Now a "double" is determined by ratio. Start with any dose you like, as long as the weight of the liquid espresso is twice the weight of the ground coffee. This is why a precision scale is such an important part of your setup, so you know exactly what you're putting in and exactly what you're getting out, every time, and can make a shot that's consistent from day to day.
How does changing the ratio make espresso taste different?
When brewing coffee, water acts as a solvent (fun fact: water is called the universal solvent). As the water comes in contact with the coffee, it extracts salty, acid, sugar, and bitter flavors out of the grounds and into your cup- in that order.
Hitting your desired ratio in about 25 - 35 seconds maximizes the flavors you want and minimizes bitterness in your espresso. Changing the ratio also changes how you experience the espresso, altering the texture from rich and almost syrupy to thinner and closer to a cup of drip coffee.
Ratio can be used as a way to express different styles of espresso- in this case, traditional Italian terms for coffee - but remember these are guidelines, not hard and fast rules.
A ristretto is going to be quite viscous, with a heavy mouthfeel, as it produces the least amount of espresso in relation to ground coffee. Ristretto style shots work well with darker roasted coffees, and can highlight sweet and chocolatey notes. They are also good for drinks like lattes and cappuccinos, as the coffee flavor can stand up to the amount of milk.
A normale, or what we think of as a standard espresso, can be considered the middle ground in terms of ratio. The current trend is to use coffee with a lighter roast than a traditional Italian blend.
These coffees are from higher altitudes, denser, and need longer contact with water to properly extract. They can benefit from a ratio of 1:1.5 - 1:2.5, which leads to a more medium bodied texture than a ristretto, as well as more clarity or brightness.
Single origin coffees can really shine when pulled as a lungo, or long shot. They will be less intense, as it’s more liquid in the cup- and the body will be much thinner.
However, this higher ratio of 1:2.5 - 3 can also pull out or clarify the individual notes, much like adding an ice cube or soda water to a single malt whisky, where the dilution makes it easier to distinguish different flavors.
Bonus fun fact: Espresso in Italy is generally pulled at a ratio of 1:3, with 7 grams of a fairly dark roasted coffee blend to 21 grams of espresso.
Allongé (1:5...or 6)
In the experimental range of espresso, using a ratio of 1:5 or higher can result in a drink that looks and feels more like a cup of drip coffee. Is it espresso? If it tastes good and you like it, does it matter?
Allongé is French Canadian- plug the word into Google translate and you get "elongate," which is appropriate for this type of espresso. This style is closely associated with Quebec and with coffee consultant Scott Rao, who developed this shot at his café in Montreal.
The idea is to pull out sweetness and nuance from coffees that are roasted light or display fruity or acidic flavors (think a description that reads: mango, passionfruit, lemon). Allongé shots are still supposed to finish in about 30 seconds- so the grind will be coarser than you might be accustomed to.
To really understand the effect ratio has, use the same coffee to brew a ristretto, a normale, and a lungo shot to see how the flavors, clarity, and body change with the different amounts of water. You may find that your dark roasted espresso blend does great from 1:1 all the way to 1:2.5, but going past that makes your shot bitter. Maybe the medium roast single origin you’ve been pulling at 1:2 tastes even better at 1:3, or 1:4.
Ultimately there is no “best” ratio for all coffees, and it's your preference that should lead the way. Knowing how to use ratio will give you a starting point on your way to a great espresso, no matter what kind of coffee you have.