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Coffee Grinder Cleaning Tips

Five Senses CoffeeAndrew Easthope 5 February 2014

A vast array of details can affect coffee quality, all of which can be controlled with the right amount of care and quality equipment. While some of these measures require fundamental investment in the appropriate equipment, there are always simple factors which can not only boost overall quality, but ensure that the only thing standing in the way of quality is the coffee you use, the equipment you’ve got and your own ability.

Following on from my last list of cleaning tips, I thought I’d write an article based on my latest OCD obsession: detail cleaning grinders. At one point in my life I would not have found any joy in this task, but the quality results which are derived from this task are stunning enough for me to have made a habit of it. Whether you’re at home or in a café, I think you should give it a shot and see what sort of difference it makes to your overall quality.

Before we discuss the method, let’s talk about why cleaning your grinder makes any difference at all. It all comes back to the fundamental factors which create flavour issues with coffee, namely prolonged exposure to oxygen and heat. It also has a little to do with how your grinder actually cuts up the coffee during the grinding process.

Oxygen and heat
Coffee is an organic, perishable product which degrades when exposed to air and heat. The longer coffee is left inside a grinder where it is exposed to both heat and oxygen, the worse it’s going to taste and behave. The vast majority of grinders will also recirculate coffee for long periods of time, meaning you’re never quite getting 100% freshly ground coffee without the occasional cleanout.

Grinding mechanics and technology
Grinders break down coffee in ways that you may not expect. Adjusting your grind size to ‘finer’ or ‘coarser’ changes the size of the particles from smaller to larger, but the resulting particles are never uniform in size. They all differ, but to put it simply, what we actually get out of a good grinder is a few large particles, a majority of particles in our target range, a bunch of tiny particles (fines) and then everything else in between.

Super-fine particles are the main reason to keep your grinder very, very clean. Being very small, they are more susceptible to the degrading effects of oxygen and heat, and due to their size and oil coating, will often end up stuck in hard-to-reach places in the grinder. Over time they will form a crust of badness which smells and tastes uncomfortably like charred peanuts. Sadly everything tastes a little like charred peanuts with a never-cleaned grinder, but I hope you never test the theory. Keep your grinder clean and be free of this madness!

One of the other downsides to many grinders is the way they are engineered to pass coffee from grinding to dosing. Most good commercial and home grinders hold on to a large amount of coffee which continues to circulate before it is pushed out, mixing pre-ground coffee with freshly ground coffee. This is where fine particles gather, unseen by us, waiting to exact their tiny revenge.

To combat this, some home-grinder manufacturers have focused on reducing the amount of coffee held inside a grinder and, over time, it’s expected that burr cleaning will be an easier task on commercial grinders. Until then, it’s up to you to find the time and energy to get your grinder clean and experience the quality boost for yourself!

How much should I clean and how often?
It’s an age old question; but how clean is too clean? With coffee, the answer is that you can never be too clean — but there’s no need to stress. You need to clean as much as you’re willing and as often as you can, and the rest depends on the level of quality control you are aiming for. Here’s the grinder cleaning schedule we employ at the ABA for our training grinders, to keep them in prime condition:

Daily/after each use:

  1. The coffee chute is sealed off and excess coffee is ground.
    – Make sure you grind off as much as possible during this step, to avoid excess coffee being inside the grinder or coffee beans sitting on top of the burrs for the next step.
  2. Turn off the power.
  3. Remove hopper.
  4. Coffee is removed and sealed in a bag.
    – Remember to keep your unground coffee sealed off and in a cool, dark place to keep it fresh. Avoid your refrigerator though.
  5. If it’s a manual dosing grinder, the blades are plunged.
    – This is the step that cleans inside the grinder and is where you’ll get the biggest benefits. You’ll need to source a ribbed toilet plunger to do this (for the love of god, don’t grab the one in your toilet right now!) The plunger should sit flush over the blades and seal over the collar. Plunge away, and make sure you’re catching the coffee which flies out (otherwise it’ll go everywhere). When plunging, you are removing a small portion of the grinds within the grinder. You’ll need to put the hopper back on and activate the grinder for a few seconds. Then repeat the above step a few times to get it really clean.
  6. If it’s an auto dosing grinder, grab a vacuum:
    – Use a nozzle attachment for your vacuum.
    – Put the hopper back on, expose the grill where the coffee drops out and hold the vacuum to it.
    – Activate the grinder to thoroughly remove all the coffee, and persist until you can only see metal around the grill. Be aware, some vacuums won’t handle this well and using a commercial vacuum is recommended.
  7. Wash your hopper to remove all the chaff. Make sure you thoroughly dry the hopper before putting it back on the grinder.
  8. Reassemble the grinder.
  9. Wipe out the dosing chamber with a damp cloth.

This is enough cleaning to see a measureable result in quality, as it stops the old grind inside the grinder from sitting there, releasing its oils, going stale and being reused. What it doesn’t address is the build-up of fine particles. To get these out, we need to disassemble the unit. For the brave and/or knowledgeable, disassembling the grinder is recommended at regular intervals (weekly to monthly), but it’s best you learn how to do this from someone who’s already experienced at it, at a time when you can absorb all the important details necessary for reassembly.

When it comes to quality control with coffee, this is the low hanging fruit. If you haven’t cleaned out your grinder to the degree outlined above, give it a shot and reap the benefits of cleaner tasting coffee!

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