BY JULIAN DAMMENHAYN

It’s almost hard to keep track of all the grinders being released these days. It’s easy enough to evaluate the specs and aesthetics of these grinders, but what do they actually do to your coffee’s flavour profile? Any barista that has spent time working in different cafes inevitably forms a preference for a specific grinder. This can be due to ease of use, ease of dialing in, workflow or, better-tasting coffee from that particular grinder. However, out of all of these qualities, taste is king. Whilst there are a large number of factors that can impact the taste of espresso outside roasting, the grinder plays the most significant role in the brewing process and can be the determining factor for how the rest of the elements come together to create the perfect shot. 

Here at the roastery, we look at grinders in two main categories: “pressure grinders” and “flow grinders”. These grinders are defined by their particle distribution: The distribution of a grinder is often broken down into separate subgroups, termed fines, mode and boulders. 

Fines are the smallest particle, they are the “dust” that some grinders produce while grinding. 

Mode is the average particle size produced by the grinder at any specific setting

Boulders are the largest particles

Pressure grinders have a broader particle distribution with more fines and boulders. A throwback to their inception, in an age of second crack, low-density coffee. New school flow grinders, in contrast, seek a higher mode with fewer fines and boulders. There are grinders out there that have distributions outside of these classifications, however, for the most part, you can look at grinders in this way.

In coffee, we must take this distribution and convert it to taste. The bridge between distribution and taste is extraction.

Pressure grinders such as Mazzer, Fiorenzato, and Gino Rossi grinders have varying degrees of fines and boulders. This is a very important factor in how they were designed and will determine how you extract your shots. Fines will extract quicker, and boulders slower, so you have to find a balance point in which you are not over extracting the fines too much, and not under extracting the boulders at the same time. There are other factors that can affect this extraction including water temp, flow rate, and basket style, to name a few. Even so, once all these variables have been accounted for, the flavour these grinders produce will naturally be a slightly heavy, and full-bodied coffee with lots of depth, making a great shot of espresso reminiscent of the classic Italian style. This kind of espresso shot is great in milk as that depth of flavour really cuts through. The fines this grinder creates will demand you run smaller shots over a longer time frame. They generally adhere to the 1:2 ratio in around 30 seconds, especially if you are using them as intended with well-developed coffee. If you run them any longer the excessive contact-time with the fines will cause bitterness and undesirable notes.

Flow grinders, such as the Mythos, Mahlkonig Peak, E65s, E80, and EK43 have a much larger percentage of particles in the mode (fewer fines and boulders). This means that a larger percentage of the coffee should extract at the same rate creating a more even extraction. We call them “flow grinders” because these grinders are better suited to coffees with higher roast density, and machines that have high pressure and lower flow rates. This means you can run these grinders with larger brew ratios without the risk of over-extracting shots. A recipe of 20grams in - 50grams out in 27 sec (1/2.5) can be easily brewed without introducing bitter notes. As a result, flow grinders will produce a very clean tasting espresso and are ideal options for highlighting the nuances of your blend or single-origins. In milk, however, this clean taste may not cut through as well, so you may need to add a little more coffee to your basket to get that same robust flavour as you would using a pressure grinder.

Understanding the differences in these grinders can help you define which style of espresso you want to serve. If you sell 90% milk coffees and your customers prefer a robust coffee, pressure grinders will be an asset to your cafe. If your clientele appreciates high-grade single origins, and you are selling majority-black coffee, you may opt for a cleaner style by using a flow grinder.

It can also help to pair your grinder and machine, as you may find that certain machines with high flow rates will not work with flow grinders, as they require reduced flow. Getting this balance right can help you fine-tune your setup to get the most out of your coffee.

The specialty coffee industry was born out of a search for greater flavour and standards in coffee, and with this goal has come a change in machinery, and burr design. Grinders overall, are now shifting to a cleaner extraction style. We hope this article helps you either fine-tune your espresso flavour profile or select your next grinder.