A Deep Dive into Refillable Capsules

Capsule machines are a great gateway into enjoying espresso-style drinks at home, without splurging for a costly espresso machine, a grinder, and all the odds and ends that go with it. For most people, this convenient solution is adequate. But as it is with many other pieces of consumer technology, there always exist aftermarket ways to “hack the system”, so to speak. One such thing we are exploring today is the use of refillable capsules. There is some degree of tinkering involved, so read on if you’re curious to see how far we can push our machine with one of these! 

The use case for refillable capsules

The easy reason is, you can use any coffee from your favourite coffee company! That may be a rare single-estate coffee, or a decaf blend you truly like. If you cannot purchase it in capsule form, then refillable capsules allow you to make it yourself! Another thing is the aspect of sustainability. While many roasters are now switching over to compostable or biodegradable materials, a reusable capsule that will last for years sounds like the environmentally-friendly option.


Which refillable capsule to use

There are three main designs: A plastic capsule with a flip-top mesh lid, a metal capsule with a screw-on lid, and a metal capsule with a “stick-on” lid, that you have to replace every time. While the other designs may aid espresso extraction a little bit better, we decided to go for the first option as it’s the cheapest, it’s 100% reusable, and the generic design makes it easy to find.


The drawbacks

As evidenced in our testing, it’s not such a straightforward process to get good results! What we’ve learned is precise coffee weights and grind settings are necessary to get a good espresso. This means that you’ll need a scale that can ideally measure to the tenths of a gram, and a burr grinder capable of grinding fine enough for espresso. You can use pre-ground coffee too, but it will be harder to dial-in, and you may end up with watery results. Yes, all capsules contain pre-ground coffee, but many roasters use nitrogen-flushing techniques to preserve freshness and equipment not available to the consumer. This all adds up to a lengthy morning ritual, much longer and more involved than the usual 30 seconds it takes to pop in a capsule and brew.


Test Bench and Methodology

First, some caution. Using aftermarket accessories, including refillable capsules, on your Nespresso machine may void your warranty!

The goal: Create a tasty espresso from a refillable capsule that displays similar taste characteristics as one pulled with a commercial machine.

What we used:

  • Nespresso Essenza Mini
  • Refillable Capsule (plastic body with mesh flip-top)
  • Mahlkönig EK-43 (with 3FE dial)
  • Digital Scale with 0.01g resolution
  • Beans: Brazil Eagle Mogiana, from Exchange Alley Coffee House in Manila. The label indicates flavours of bittersweet chocolate, roasted nuts, and apple.

We used a commercial burr grinder for this experiment. It may be a bit out of reach to the home user, but it is a popular model for cafes and home enthusiasts. This can hopefully provide a reasonable approximation of grind setting - one that you can ask your barista friend about, and is also easily researchable online. For the grind setting, we settled on three levels for this experiment: Very fine, fine, and medium-fine (marked on our EK-43 as 2.5, 4.5, and 6). For comparison, our commercial espresso machine was pulling shots at the 4.5 setting that day.

In a previous article, we found that capsules contained between 5-6 grams of coffee. We found it difficult to consistently fill the reusable capsule to this level, so we limited the experiment to two specific doses: 4.5 grams, and 5.5 grams.

Tamping the grinded coffee

(We had to get creative with stuffing our capsule with 5.5 grams of coffee. The flat end of a muddle bar spoon worked nicely as a tamper!)

Summary of Testing Variables:

  • Grind Setting: 2.5, 4.5, and 6
  • Dose: 4.5 grams and 5.5 grams
  • Nespresso Essenza Mini, button held down for a manual brew time
  • Target Brew Time: 25 seconds 

Results

Test

Coffee Weight

Grind Setting

Shot Yield

Result

1

4.5g

Very Fine

10g

Intense, Salty. Strong and under-extracted

2

5.5g

Very Fine

~1g

Pump stopped after 3 seconds.

3

4.5g

Fine

25g

Intense, but sweet. Terrific with milk.

4

5.5g

Fine

12g

Pump stopped after 10 seconds.

5

4.5g

Medium-Fine

60g

Balanced, but watery. Good as is.

6

5.5g

Medium-Fine

15g

Pump stopped after 15 seconds.

 

Our machine’s pump stopped on all of our tests with 5.5g of coffee in the capsule (Tests 2, 4, and 6). Word to the wise: if your pump stops early on in the extraction, wait at least a minute to relieve the built-up pressure in the machine, before discarding the capsule. If not, you may get an aggressive burst of pressure, which may be accompanied by grounds flying everywhere! Here we see the limitation of a reusable capsule. Single-use capsules are not meant to be reused, and therefore can get away with thinner materials. This allows for a bigger cavity for coffee grounds, which allows the pump to successfully push water through more coffee. Needless to say, all our shots that used 5.5 grams were simply a few drops of undrinkable bitterness.

The meat of our experiment lies with Tests 1, 3, and 5. While the Very Fine setting was a little bit too intense and salty, our Fine and Medium-Fine setting gave us our favourite results. Test 3 was similar to a ristretto - enjoyable on its own, but probably tasty as a small cappuccino. Test 5 highlighted the best flavours (we did get chocolate, nuts, and apple notes!), but the longer shot reminded us of a long black, lacking the intensity of the other two.

Tests 1, 3 and 5

(Tests 1, 3, and 5 yielded drinkable results, depending on how you like your espresso)

Conclusion (or should you do it?)

Yes, with a big IF. All our tests used freshly-ground coffee, pulled after no more than 10 minutes after grinding, on an industry-standard commercial grinder. Packing the reusable capsules with coffee was a chore in itself - we had to get creative with tamping down the coffee, just to fit coffee into our thicker reusable capsule. The results do speak for themselves - if you dial it in correctly, you can achieve an espresso that will do your chosen coffee beans justice. However, the amount of work required may discourage people who are happy with just popping in a ready-made capsule. It’s a fun experiment that makes you bring the best out of your capsule machine, but we don’t see this replacing our morning routines anytime soon.

Words by Jon Choi @theheadbean

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