What's the most effective way of generating crema from an Aeropress?

Question

I know a number of people have become fairly capable at getting a nice amount of crema at the end of the process of making a cup with their Aeropress.

I, however, am getting just a very thin, partial layer at best. I've experimented with pressure, and somewhat with water temperature.

Wondering if there's a magic bullet, or a good list of bullet points of things to do to maximize crema?

Answer 1

Here's a quick rundown of the Aeropress method I use every morning. I end up with a relatively crema-y shot. You'd never mistake it for one from an espresso machine, but there's a good layer all across the top.

This is completely unscientific and I can't identify which steps here are the relevant ones for the good results, but maybe if you experiment with some of these adjustments you can identify what works and what doesn't.

The Equipment

• Aeropress
• Scoop that came with the Aeropress
• Ultra fine mesh filter

The Coffee

The beans I use vary; I generally grab a light or medium roast off the shelves at Trader Joes and grind it one click down from the finest setting on the in-store grinder. (The finest setting purports to be for Turkish coffee; the one I use is labeled 'espresso'.)

I store the ground coffee in its can in the fridge for up to a week or a week and a half, depending on how long it takes me to drink it all. Today I'm using Trader Joe's Jamaica Blue Mountain Coffee, a delightful medium roast. (I just now learned that Serious Eats says it's the best bet for Trader Joe's coffee.)

The Water

Melted snow from the Wasatch Mountains, filtered through whatever the county of Salt Lake does before it gets to my kitchen tap, and heated on the stove until just before the boil. There are tiny bubbles forming on the bottom of the kettle, but few of them are rising to the surface of the water.

The Method

I'm pretty loosey-goosey about my brewing method, but the results are very consistent. This leads me to believe it's the equipment and the beans that are generating the great results, not anything I'm doing right.

1. Set up the Aeropress for inverted brewing.
2. For one shot, use a generous scoop of ground coffee. Tap the assembly on the counter so the mound of coffee flattens out.
3. Slowly add your just-off-the-boil water. (I use a gooseneck kettle for easy, controlled pouring.) Rotate the Aeropress as you pour and do so until you can no longer see any dry grounds. (The chamber should be about 2/3 full when this is complete.)
4. Stir slowly until you get that lovely uniform light brown color on the top of the mixture. I use the handle of the scoop for stirring.
5. Place the cap and filter on top of the assembly and wait 15-60 seconds. (My own brewing time varies wildly, depending on what distracts me during that time.)
6. Press. With this fine grind and filter, you'll have to press a little harder than with the coarser grind. As you press you'll see foamy buildup gather on top of the grounds. You'll have to press extra hard at the end to squeeze all of that through, but it will drip down onto your shot at the end and form that delightful crema.

Edit:

As I pay more attention each morning, I've noticed a couple more things:

• My results vary significantly. I think the contributing factors are the grind and how hard I press at the end.
• I never use soap on my Aeropress equipment. I rinse it with tap water after each use, but never run it through the dishwasher. There may be buildup of coffee oils on the surfaces that helps (or hinders??) the foam making process.

Edit Redux:

For the past few weeks I've been casually experimenting with my morning coffee and coming up with very inconclusive results. (As I mentioned below, all I've come up with are a bunch of totally surefire ways to absolutely demolish the crema, and no methods of preserving it.)

This half-butted casual science ends now! I just bought a hand grinder and an app full of AeroPress recipes; thusly armed, I'm going to experiment more formally. Well, a little more formally. I'll track the results here and update this answer when and if I come up with a reliable way to generate and preserve the foam on my AeroPress shots.

Edit The Third:

The results are in: I've figured out how to stop killing my crema. It turns out that the combination of freshly ground beans and the mesh metal filter is somehow stopping the crema from getting through to the cup. Eight attempts with hand-ground beans failed miserably, and my first attempt after reverting to store-ground beans (with the 'somewhat loosey-goosey' method above) generated a nice layer of foam in the cup.

However, the plot thickens. My colleague Robert asserts:

Never had a problem getting crema with aeropress. Lots of fresh coffee ground to a powder, very little very hot water. Makes my ubercoffee syrup shots I talked about a year or more ago... with plenty o crema. Dilute to taste (which I never did < jitter >).

...and I'm not entirely sure, but if memory serves, switching to the fine metal mesh filter meant bye-bye to crema. It's been a bit too long to remember for certain. I just reused the same paper filter over and over for months (actually, I used two to keep them from blowing out).

So it would seem that:

• Freshly, very finely ground coffee + paper filter + not much water = crema city
• Coffee ground fine in the store + metal filter + water = crema town

I'd be interested to see others' results from experiments like these.

Answer 2

Ok, I'm mega late to the party but sharing's caring so here goes.

We've all seen that aeropress sometimes produces a foamy, oily, tasty product on top of its shot and sometimes not. Without entering a geek war of whether this is or isn't traditional crema, let's just assume that this is what the OP wants when talking about crema so we can all be on the same page.

Using the inverted method, the crema is the last thing to come out of press because it's lighter than the coffee hence why it floats to the top. However, if you leave an air gap when you fit the cap and then flip the press without removing the air gap then the last thing to come out of the press will be this air.

Furthermore, if you wait until you hear the air escaping when you're pressing down, which will be once the coffee liquid has all come through, and then hold the press horizontally as you squeeze out the "air" then inside the press you will have: a small reservoir of coffee liquid; a pocket of air; and, in between, the crema. Since the press is now horizontal, all three of these things will be against the filter and so will all be trying to escape.

Continue to squeeze until you can do no more. Again, since it is horizontal, the final drips will collect at the rounded tip of the filter cap and be able to drip into the cup. If it was vertical, as for the initial part of the pressing, the liquid would be evenly distributed across the flat, circular base of filter cap and be unable to drip.

A quick flick into the cup catches the last remnants of the oily foam we're going to call the crema.

Answer 3

You really shouldn't expect to get good crema from the Aeropress. To get a good crema, you need pressure, far more pressure than you are able to generate by hand. I roast my own coffee, so I can brew it within days of roasting. I get a nice foam during the process, but this is different than crema.

Answer 4

In addition to abby's answer. The freshness of the coffee beans can have a large effect on the amount of crema produced. I've found that beans that are more than 3-4 weeks from the roasting date start to produce less and less crema.

As coffee beans age, the oil starts to migrate to the surface of the bean and begins to oxidize (and its the oil in coffee beans that produces crema)

Answer 5

Crema is a foam of coffee oils, carbon dioxide- and air bubbles entangled in coffee grounds. (There is an exhaustive Coffeegeek article on the subject.)

When extracting coffee using Aeropress, the foam floats up, gets filtered last, and gets trapped in the grounds and paper filter.

Use inverted aeropress with something to catch the crema and a stainless steel filter.

To maximize crema use fresh beans, grind right before brewing, and do not exceed 204F/95.5C water temp.

More photos in my blog

Answer 6

TL/DR: That's the one: How to Make REAL Espresso With a $20 Aeropress! - Tutorial (YouTube).

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I have had the aeropress for a couple of years, but only recently I started trying different methods of making coffee.

I have run several experiments (I didn't document them. hat's off to andy!), and I have read a lot about what really IS an espresso, and how it's made.

So...

First of all, what most people are creating with the aeropress is NOT crema, but foam. There is only 1 way to create crema, and it needs some extra equipment. Pressing down REALLY hard ! These guys have nailed it.

Also Spressa Mezzo is probably doing a good job. I can't find it locally though :(

Some science (sorry I lost all the links...): Espresso is defined by making hot water run through tamped ground coffee at around 9 bar pressure. Only then the oils are extracted. The process of extraction generates the crema.

So for aeropress, in order to generate 9 bars, the math tells that you have to press it with 294kg (plus some extra bit that I don't know how to calculate...). Let's call it 300. So you need a lever to do that. And you have to make the lever's math work out because you need as close to 9 bar as possible. More or less will not make an espresso.

That said, what I personally do is this: How to Make REAL Espresso With a $20 Aeropress! - Tutorial (YouTube).

It is NOT "real" espresso, but I think it's the closest thing you can. And definitely the best method for aeropress.

One last thing: if you don't use a lever, which could actually generate crema (real espresso); don't worry about whether foam is created. It doesn't make a difference.

No... this is the last thing: With said, preferred method, timing doesn't matter. Personally that makes me enjoy more the process.

Answer 7

The quite-foolproof method I found best for daily use. Result is, as far as I can taste, comparable to the commonly buyable espressos. Crema starts disappearing a bit faster than from presso machine, use smaller cup if you want it to hold longer.

• Coffee choice helps, but most important factors can be reduced to keeping the roast fresh and adding some robusta for more fun&crema.
• Quality water helps. Interestingly, crema amount, quality and retention can be reduced to similar variables as with beer (except there's more literature for beer on this topic) -- The more long, non-polar molecules dissolved in the water, the better. The more short polar molecules (e.g. minerals, salts, simple sugars), the less crema. Trace amounts of detergents are terrible for crema.
• I use around 1 scoop of extra fine grind
• brew non-inverted, with fine steel filter:
  1. Tamper the grinds down to a compact, uniform puck. As hard as possible. This helps: http://www.thingiverse.com/thing:1523667
  2. Add around 1 "aeropress unit" of water, boiling right from the kettle. Pour the water slowly over a bent spoon, so it doesn't impact the grounds with too much force, and the coffee puck stays intact&holds together. Some people use extra paper filter on the grounds, but I wasn't able to see any significant difference (apart from the wasted filter). The spoon cools the boiling water down a bit, and I found no improvement in any further temperature adjustment.
  3. Don't wait (there's no steeping) and press it down with all your might. Stop just before squeezing the grounds. Whole pressing should take ~20sec. Always apply maximum force -- if the pressing goes too fast, use finer grind or more coffee (instead of less force) to make it slower; If it's too slow or stuck, use coarser grind.

EDIT: added water quality factors.