What's the Ideal Dose for a Shot of Espresso?
Why do you use 18g of coffee for your shot of espresso? Is it because that’s what you read on the internet? Or what we told you to do? Is your dose keeping you from your best espresso? Let's explore how changing your dose in your espresso recipe can help you make better coffee.
The dose is the amount of coffee, in grams, you put into your espresso machine. Throughout our blogs and videos, you’ll find that we typically recommend keeping your dose the constant variable in your ever-changing espresso equation. We’ve advised you to choose your dose based on the basket size you have and how much coffee you want to pull. If this is new to you, pause this video and take a moment to watch our Guide to Pulling the Perfect Shot and The Perfect Espresso Recipe to make sure you have the basics down before continuing.
When building a recipe and pulling a shot, the goal is always a great-tasting espresso — and a proper extraction is how you get that. Extraction is the technical term for how much of the coffee’s flavor ends up in the cup. We grind coffee very finely to help water break apart the chemicals in a coffee bean and dissolve them into the water, resulting in a flavorful, drinkable beverage. As your shot pulls, the acids, fats, sugars, and fibers are all extracted. The ideal extraction is a combination of these compounds and is dependent on many factors: the coffee itself, the level to which it’s roasted, its age, how it’s stored, how it’s ground, the quality and temperature of the water, your brew ratio and how much time you allow it to be pulled — or extracted.
Today, we’ll focus on achieving a great extraction by changing dose, grind size, and using pre-infusion.
Basket Depth and Portafilter Size
As water runs from the group head through the puck of coffee and begins extracting and pulling flavors from the coffee, it grabs everything it can from the grounds but it hits a point where it can no longer hold onto anything else. This means all the coffee at the top of the bed will be thoroughly extracted and all the coffee towards the bottom may not be. The larger the distance between the top and bottom of the puck, the bigger the difference in extraction.
An even extraction occurs when coffee is ground as uniformly as possible and each particle gets the same water contact time. This results in the most flavorful and transparent coffee. Using smaller doses means increases the chances of all the grounds extracting evenly.
This makes a considerable difference if using a recipe given for a coffee made in a 58m portafilter vs a 53 or 54mm portafilter. Take a look at the difference in depth between these portafilters with 20g baskets. If you want a similar extraction to occur, a smaller dose would need to be used for a 53mm given what we just learned. But that means a different grind size would be needed.
When you change your dose, there will be a change in brew time which means you may need to change your grind size. If you increase your dose, you may need to coarsen up your grind to achieve a target extraction to compensate for the influx in coffee. If you decrease your dose, you may need to grind finer to compensate. Since brew time is so quick for espresso, having many fines is ideal and essential for a good extraction and a great tasting shot. A lower dose allows you to grind finer which can increase extraction to improve flavor. However, with a smaller dose, we increase our chances of channeling.
If you’ve been pulling shots for a while, I’m sure you’ve experienced your fair share of channeling. Channeling occurs when water finds a specific narrow path through the puck of coffee instead of flowing through the entire bed evenly. Over the course of the shot, this path will have a greater flow rate causing areas of localized over-extraction and leaving the rest of the coffee bed under-extracted contributing to unbalanced flavors to the final shot. There are many reasons channeling occurs but a smaller dose or lower bed depth makes it easier for channels to form. So this means there is a limitation or minimum dose before you really start to see and taste the effects of channeling in your shot. You’ll want to figure out how low you can bring your dose and how fine you can grind your coffee before you see the classic signs of channeling. The worst part about channeling is that it happens either way, whether you can see it or not.
The idea behind pre-infusion is similar to that of a coffee bloom. With espresso, we use pre-infusion to saturate the entire bed of coffee with water so that when we engage the pump and blast the puck with nine bars of pressure, all parts of the coffee bed have an equal chance at a similar extraction. Pre-infusion can help reduce channeling. The amount of pre-infusion time should be dependent on your dose. With a deeper bed or higher dose, you’ll need more time to saturate the puck. If your machine has a fixed pre-infusion, try to lower your dose enough so that by the time the pump turns on, you’re already seeing the espresso collect on your portafilter basket. The ideal amount of pre-infusion time is however long it takes for the entire coffee bed to saturate — right around first drop would be a good time to increase to full nine bar pressure.
Adjusting your dose is a great way to enhance the flavor and extraction of your espresso. Your ideal dose should be the lowest you can go before channeling occurs and this threshold will be different for everyone. It depends on your machine and the pressure it’s able to build, your grinder, and your technique. Channeling occurs even when we can’t see it and its impact on flavor can be detrimental. The only way to figure out what dose will be best is by trial and error, and lots of tasting. Let us know your thoughts and comments below.