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Flow control is the latest trend in espresso. It’s a tool to help you get more out of your coffee by extracting specific flavors, aromas, and nuances out of your favorite coffee. Now, it’s more accessible on prosumer-level home espresso machines from manufacturers including Profitec and ECM, as well as high-end home and commercial machines like Dalla Corte’s Mina.
If you’ve been looking for more details on how to determine your flow rate on an E61 group machine, you’ve come to the right place. We’ll be using the ECM Synchronika and the Dalla Corte Mina to discuss how we determined our flow rate using really fresh coffee on these machines, but first, let’s give you a quick rundown on what you can do with flow control.
Flow control allows you to use the flow rate of water to adjust the flavor and aromas of your coffee. If you have a very fresh coffee, you can use flow control to allow the COz to off-gas and control the brightness of your coffee. If you have an old coffee, you might want to start off with a high flow in the beginning and gradually reduce the flow to improve mouthfeel, and prevent extracting stale and oxidized compounds.
You can also use flow profiling and adjust the flow rate to cater to a particular roast level. For example, you can do a gentle pre-infusion for a light roast coffee and a more aggressive pre-infusion for a dark roast. Another impressive feature is the ability to replicate extraction characteristics of manual lever and pressure profiling machines, and if you like the occasional filter coffee, you can grind coarse and use a low flow to turn your machine into a single-serve filter coffeemaker. As you can see, flow control opens up a new world of possibilities and can brew your favorite coffee exactly how you like it with the right variables.
Now that you have a better understanding of flow control, let’s talk about flow rate and how we can adjust it during extraction to find the sweet spot. Take the Mina for example: it’s easily programmable through the Mina app based on the digital flow rate and timing in 5 steps. From there, the digital flow meter in the machine takes care of the rest. However, if you’re using an E61 flow control device, here’s how you can determine the flow rate.
For anyone who needs a quick look at flow rate compared to the number of turns of the flow control device / valve, here's a few graphs for both vibration pump and rotary pump machines.
The results from our measurements ranged from 1.5 grams per second at an eighth of a turn up to about 11 grams per second at one and a quarter turns open. By calculating these measurements and following this formula, you’ll know how far to open your flow control knob to get your desired flow rate.
If you’re working with a really fresh coffee, here’s an example of what you can do to get the best results from your extraction. This profile comes from World Barista Championship judge Danilo Lodi, who used the Dalla Corte Mina to pull some incredible shots with fresh coffee. We recently spent some time with Danilo at George Howell Coffee in Boston, where he pulled some impressive shots on the Mina using one of George’s Kenyan coffees.
Here’s how to do it. On the Mina, program the profile and the flow meter and let the machine take care of the rest. If you’re using an E61 group machine, you can do the same thing now that you’ve figured out the positions to get your desired flow rate. For our flow rate, we calculated 60 seconds at a quarter turn and then five seconds at just under half a turn. We then reduced the flow to finished the extraction a little over a quarter of a turn. We used an ECM Synchronika which has an automatic shot timer, so getting accurate timing was simple and convenient, and only required us to keep an eye on the timer.
This profile works wonders with super fresh coffee because the gentle start allows the CO2 to off-gas and decrease the bitterness compared to what you’d get with a full rate extraction of a really fresh coffee. By keeping the flow gentle and finishing off where it started, this helps to extract the sugars and flavors of the coffee and really build a sweeter aftertaste.
The process described above is just one example of how you can use flow control to improve extraction, and how to calculate the measurements to achieve your desired flow rate. There’s a lot more to the conversation on flow control and flow profiling.
Below are different flow profiles we've tried and tested that offer best results for different circumstances. For example, we have a profile for brewing a coffee shot, for fresh light roast coffee, for not-so fresh dark roast blends, for emulating lever machines, and one more for adding a sweet bump in flavor.
We're always experimenting with flow control and working on our own flow profiles to share with all of you. If you have a machine with flow control, you should keep experimenting, too! That's part of the fun, anyway, so don't be afraid to try different things and drink your mistakes. Soon enough, you're sure to find something truly special, discovered by you.