Coffee Prosumer Uses Particle Size Analysis To Test Coffee Grinders – CoffeeTalk

The size of your coffee grounds determines how fast your brewer can extract flavor and which flavors get pulled out. Uneven coffee grinds, with ultrafine particles or giant boulders, will cause uneven extraction, resulting in bitter or muddy coffee or a failed shot of espresso.

In the last decade, there has been more attention paid to grinder minutiae, grinder results, and grinder tech. Now, it’s rare to find anyone who cares about coffee using a cheap, old-fashioned blade grinder, which roughly chops coffee beans with spinning steel. The new wisdom is that only burr grinders will do. Conical burrs are like a many-angled drill bit, crushing and funneling and finally cutting each bean. Flat burrs, on the other hand, are like spinning wheels of death that rotate against each other at a set separation.

However, it’s hard to know how well a coffee grinder is actually working or even the basic rules behind what types of grinders create what flavors. Technical-minded coffee influencers like Lance Hedrick have been open about throwing up their hands when it comes to broad generalizations about how different types of grinders perform.

When testing grinders, much of the hard work is often done simply by taste test, comparing flavors yielded by different grinders with the same beans. Up to now, the best objective home tool for assessing grind precision was to pour coffee grounds through a set of sieves and see how much coffee was left.

The DiFluid Omni ($900) is a new device that allows home coffee enthusiasts to graph the particle size distribution of a batch of coffee. It also has a colorimeter for assessing the lightness or darkness of a roast. This is the first time it’s possible for someone at home to assess how good a grinder is.

The most popular grinders are the Fellow Opus and the equally priced Baratza Encore ESP. The results of this first round of particle analysis show that the Fellow Opus is the most popular, followed by the Baratza Encore ESP. Higher-end burr grinders are demonstrably better than budget grinders, and the Omni works as advertised.

To test each grinder, the same coffee beans were tested from the same batch, using medium grinds for drip or pour-over coffee and nearly the finest grind each grinder was capable of, usually an espresso grind. At least five tests were run for each grind size, using DiFluid’s CoffeeOS app to collate and visualize data. Each test involved using a wee sampling of coffee grounds, spread across the white circular base of the Omni using either the brush or the device’s vibration function.

The top of the Omni has a camera whose lens faces the circular base with the coffee grounds on it, capturing the size of each ground, assuming the grounds are dispersed appropriately. The results of this analysis provide valuable insights into the performance of different types of coffee grinders and their potential applications in home coffee analysis.

The Baratza Encore ESP had the most precise results at very fine grinds, with about 30% of the coffee grounds huddled in peak range. The Fellow Ode Gen 2, a flat burr grinder, produced a textbook-looking normal distribution at medium grinds but a flat distribution at finer grinds.

The Technivorm Moccamaster KM5, a flat burr grinder, showed quite precise results across the board, rivaling the Encore ESP at fine grinds and the Ode Gen 2 at grinding for drip. Moccamaster is a well-trusted coffee brewer brand known for its analog precision, but it’s not known for grinders, and without this particle analysis, the author might not have clocked how well it did.

The conventional wisdom is that flat burr grinders are precise, and conical burr grinders are more likely to show a balanced blend of grind sizes—bringing out sweetness, depth, and chocolate. However, raw data from particle analysis showed mixed results even for the same grinder, depending on the coarseness or fineness of the grind setting.

The Kingrinder K6 hand grinder behaved much like the Ode, with a nearly textbook bell-curve distribution surrounding a central peak. When dialed tighter to espresso-fine grinds, the K6’s curve compressed to what looked like a slender butte: Grind sizes stayed fairly even, across a tightly compressed range.

However, precision is relative. A surprise from this testing was the extreme variability of coffee grounds within each sample, among all grinders tested. Coffee grounds aren’t one size or another; they live on a continuum. The sweet spot for brewing coffee in any given style is a window of just a few hundred microns—and yet, the standard deviation for the grinders tested was rarely less than two hundred microns.

Coffee grinders invariably spit out a range of both large and small particles. A range of coffee particle sizes isn’t bad, necessarily: this can lead to balance, depth, and complicated toffee or chocolate notes. Tight particle distributions will more likely express more specific aromatics, like bright cherry or funky plum.

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