It’s no understatement to say that the grinder is one of the most important pieces of equipment in any coffee brewing setup. Without a high-quality grinder, it’s difficult to achieve even grind size distribution, which will in turn affect the quality of your extraction.

But no matter how powerful your grinder is, cleaning and maintenance will be vital to making sure you get the best out of it. By regularly maintaining your burrs and cleaning your grinder, you will make sure you brew consistent, delicious coffee time and time again – whether you’re at home or behind the bar.

However, there are a number of ways that you can do this. To learn about some of the best, I spoke to two coffee professionals from Fiorenzato – a premium coffee grinder manufacturer. Read on to find out what they told me.

You may also like our article on coffee grinder burrs and what home consumers should look for.

Why is it important to clean your grinder?

During the roasting process, heat causes gases to release from the coffee beans as their cell structure breaks down and becomes more porous. This is why roasted beans are far more brittle than raw green coffee – which both home and commercial grinders alike would struggle to break down.

However, roasted coffee also contains oils. These are lipids that naturally migrate to the surface of the bean during the roast.

Marzia Viotti is a Technical Trainer for Fiorenzato. She explains how and why oils remain in the grinding chamber. 

“Coffee oils stick to the teeth of the burrs,” she says. “Over time, if left there, the odour and flavour of stale coffee will affect any new coffee you are grinding.”

The “teeth” of your grinder burrs are the small ridges and crevices that sit around the edge and surface – for both conical and flat burrs. Although the angled design of these teeth helps to grind coffee both evenly and quickly, it also means oils and very fine coffee grounds (also known as fines) stick to them easily.

It’s not just the burrs that are affected, either. As fine coffee grounds accumulate over time, they may cause blockages, which can in turn lead to mechanical problems.

“Extraction and flavour are affected by any lack of cleaning,” Marzia says. “If old coffee gets stuck in the spout, the coffee doesn’t didn’t come out properly, so the performance of your grinder could be affected.”

Blockages in your grinder – specifically in the chute coffee falls through into your grounds bin – will then lead to fresh coffee becoming contaminated with old, stale grounds. This in turn negatively affects flavour and aroma. 

“In addition, it will affect your grinder’s output, and your grind speed will become slower,” Marzia adds.

What is grind retention?

Grind retention is where ground coffee remains inside the inner grinding chamber and spout. While your burrs will always retain a certain amount of coffee, this will vary depending on their shape.

Some amount of retention can be beneficial for reducing static and maintaining a consistent grind flow, but high levels are detrimental. If old grounds are not regularly removed, coffee freshness and grinder performance can be compromised.

“Coffee retention is a popular topic now,” Marzia says. “This is because coffee lovers are more aware than ever of the importance of always having freshly ground coffee.”

Flat burrs tend to retain more coffee grounds than conical burrs because of the differences in the grinding mechanism. 

For flat burrs, coffee is ground between the horizontally-aligned top and bottom burrs. These force the grinds sideways into the inner chamber and spout.

In contrast, with conical burrs, the top burr sits “inside” the bottom burr. This means gravity forces the coffee grounds through the chamber and spout, and as a result, the set retains fewer grounds.

Giulia Bagato is the Marketing Manager for Fiorenzato. She explains how the company’s Pro line of commercial and prosumer grinders have been designed to mitigate grind retention.

“The grinding chamber and its components have been redesigned to reduce the inner space, so there’s less residual ground coffee inside it.”

The new design allows baristas and home brewers to easily remove the top burr for easy cleaning and maintenance. After removing the hopper, the user can take it out using two clips on both sides of the grinding chamber. 

To separate the burr set on a commercial or prosumer grinder, users would typically have to unscrew the grinding chamber’s casing. This takes more time and can be detrimental to service in a busy coffee shop.

Clumping & cleaning 

As ground coffee contains moisture by default, it often sticks together in small clumps. This is also caused by static electricity, which is generated as burrs spin continuously at a high speed.

This clumping can bring about a range of issues, but chief among them is uneven grind distribution in the brewer or portafilter. In turn, causes channeling, which is where water finds the path (or channel) of least resistance through the coffee bed. 

Channeling means water bypasses the more compact areas of coffee, leading to a combination of under and overextraction, which causes the cup to carry more undesirable flavours and aromas.

“In each on-demand Fiorenzato grinder, there is a clump crusher,” Giulia explains. “This is a small tool that prevents coffee from clumping and allows static electricity to disperse.

“In the Pro Line, our clump crusher was reshaped to be more effective against clumping and to allow users to clean the whole grinding chamber more easily.”

A clump crusher is particularly useful when grinding for espresso, which requires a finer grind setting. This is because clumps form more frequently when you grind finer.

“Other grinder models have the clump crusher outside the grinding chamber at the end of the spout,” Marzia says. “With the Fiorenzato Pro range, the clump crusher is at the beginning of the spout. This means the coffee grounds can pass through more easily.”

This design decision helps to minimise static, which stops more clumps from forming, but also reduces the amount of dust and chaff that accumulates. For busy cafés, cleaning this helps to maintain your workstation, but can also affect service during busy periods.

Grinding fresh coffee

Many flat burr grinders can retain anywhere from 1g to 12g of coffee per dose. This makes it difficult to know how much of the coffee you’re brewing with is fresh, and how much of it is stale. 

Once coffee is ground, its flavours and aromas will begin to degrade as it oxidises. This process causes the more subtle characteristics of a coffee to fade and disappear. The heat created by a grinder’s burrs also causes retained grinds to lose flavour even more quickly.

Purging the grinder of stale grounds helps to guarantee that the coffee you’re serving or drinking is fresh and served as intended. 

But as well as enhancing the experience, purging also enables baristas to work more efficiently. Grind retention can stop baristas from dialing in effectively, as retained grinds can be expelled into the portafilter after a change, the new grind setting has yet to come into effect.

This makes it difficult to track and as a result, the barista can end up changing the grind too little or too much. This means their shots end up running too slowly or too quickly, and it takes them longer to find a “sweet spot” for extraction.

To remedy this, it is recommended to purge up to 12g of coffee after making changes to the grind setting.

Burr quality also affects grind retention and extraction quality. The sharper and more robust a burr set is, the longer the grinder will perform at its best.

“Fiorenzato chose Bohler M340 food-grade steel for our burrs,” Giulia says. “It’s important that the materials in contact with coffee don’t release harmful substances, and our burr material hardness guarantees a longer lasting sharpness.”

Cleaning and maintenance: Some tips

Regular cleaning your grinder is key – it is totally necessary for maintaining coffee quality. 

Marzia says: “Coffee gets stale after three days, so grinders should always be cleaned after three days, at least.

“It can be intimidating for baristas to clean grinders, especially new baristas or those with less experience.”

Despite these concerns, cleaning and maintaining your grinder is important, and helps you get the best results from your coffee. The best place to start is by making sure your grinder is turned off and disconnected from any power source. 

“You don’t need any tools to clean Fiorenzato Pro grinders,” Marzia says. “With some grinders, when you change the burrs, it’s hard to detach the chamber because there is a thread inside.” With the Pro, she notes, the grind chamber is entirely detachable, which grants the user easy access.

However, remember that separating a burr set will typically disrupt its thread and cause the grind setting to change. That said, some grinders, such as the Fiorenzato Pro, have a detachable top burr which allows the grind setting to remain intact during removal and cleaning.

Marzia suggests another way to clean your grinder without losing the setting. “You can clean a grinder easily with a small vacuum cleaner and you don’t lose the grinding point,” she says.

She adds: “If you are using a dark roast, I suggest cleaning the grinder daily with a vacuum cleaner. However, the burrs need to be cleaned with the professional products designed for burrs every three days.”

These professional products usually come in the form of food-safe pellets which can be ground and run through the grinder, much like coffee beans. They absorb oils from the burrs and expel any retained grounds. 

After doing so, purging the grinder by running a few grams of old beans through helps to remove any remaining fragments of the pellets.

“Espresso is often very oily, as you grind the beans finer and the beans are often darker,” Marzia explains. Cleaning grinders designed for extracting espresso, such as Fiorenzato’s Pro range, is even more important, especially in a high-use environment such as a coffee shop.

During busy periods or when you have limited time, cleaning the inner chamber and spout with a soft-bristled brush will be adequate. However, Marzia recommends that for more intense cleaning, professional cleaning pellets are the only way to go.

“With just a brush, you will not remove the oils,” she says. “Professional products will do so, and can keep the burrs cleaner for longer.”

In order to get the most out of your grinder, regular and thorough cleaning is essential. Not only will this enhance performance, it will also improve accuracy and consistency.

By following the advice in this article, and making sure you use professional-grade products at least semi-regularly, you’ll be able to reap the benefits of a clean and well-maintained grinder.

Enjoyed this? Then read our article on coffee grinders and the difference between conical & flat burr grinders.

Photo credits: Fiorenzato

Perfect Daily Grind

Please note: Fiorenzato is a sponsor of Perfect Daily Grind.

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