What Does Coffee Bed Shape Tell Us About Extraction?


What Does Coffee Bed Shape Tell Us About Extraction?
  • The shape of spent coffee grounds (the 'bed') after making a drip/pour-over style coffee can give us useful information about the brew.
  • If the grounds are convex/going up the wall of the cone/basket then likely the grind was too fine.
  • If the grounds have divots in them from the pouring water then likely the grind was too coarse.
  • The goal is a flat bed - no grounds on the sides but also no divots or mounds.
  • This could also be affected by water pour rate so it is just one thing to look at - other variables have to be taken into account also.

Transcript (Speaker: Adam Marley)

Hey, everyone. Welcome back to another Tips and Tricks with Adam. Today we're going to be talking about pour overs and batch brew or drip coffee. The tip for this week is to always check your bed, and that'll make sense in a second. Today, I have some props. I'm recording this Tips and Tricks live because I just discovered that iPhone will not allow me to flip the camera in the middle of recording a video preemptively, like beforehand. So I'm going to do this live, so I can flip my camera, because I've got a prop. So I'm going to start with having a drink of coffee.

I want to start with saying that what we're going to be talking about today, the tip for today is a technical one about what you can learn from the spent grounds after you've made a pour over or put on some batch brew, some drip coffee. But as always, taste is king. So don't look at your bed and then go, "I'm going to make some changes," if the taste is perfect. Now, you might really enjoy the taste. Today we're not really talking about under or over extraction. You might really enjoy the taste of the coffee that you've made, the drip coffee that you've made, but it might be better. It might be able to be better.

So by looking at the spent grounds after we've made a pour over or put on some drip coffee, we can get a good idea of how even that extraction was during the brew. And maybe our extraction wasn't particularly over or under extracted, but if it was uneven, what we've done there is probably ground coarser. If, say, we didn't taste over extracted, didn't taste astringent, because it's uneven, some of the grounds in that brew, we're talking filter coffee here. So although this kind of applies to espresso as well, but you can't analyze it afterwards, but we'll get into that in another Tips and Tricks.

So maybe you had your grind setting right, or your variables right, so it didn't taste astringent, it didn't taste over extracted. However, if the brew was uneven, then what's going to happen is you did over extract some of that coffee. What you did was grind coarse enough to compensate for that, and make sure that the most over extracted coffee in that brew wasn't too over extracted. But what it means is you've probably under extracted part of that brew as well. So instead of getting this perfectly in the middle, everything's really well extracted, what you've done is kind of gone the two tails on either side and made sure that the bitterness and sourness from the over and under extraction have kind of balanced each other out. I mean, that's not exactly... sorry. It paused due to poor connection. Great job, Australia.

So, that's not exactly what's happening, but it's a pretty good way to picture it. So I'm going to flip my camera. Whoop. Cool. And so this is the Breville Precision Brewer. I've been testing this at home. We're looking to see if we want to potentially sell these, resell these on the website. So far, I'm quite happy with it. It's not perfect, but I'm quite happy with it. So, might be pretty obvious to most people, this is a drip coffee brewer. So we have a Thermos of coffee here, and then in the top is our filter basket.

So if we look here, this is the coffee bed from the coffee I put on this morning. Now what you can see is, first of all, I'm going to look at this and go, "This isn't too bad." What I'm looking for, what I want to achieve is flat of a bed as possible. I don't want too strong divots from the shower head or from my pouring kettle. This applies to pour overs as well. But I also don't want high and dry grounds coming from the side.

Now it's a little bit hard to see, but you can kind of see, I do have some high and dry grounds. I do have a little bit of a divot. So, if we flip back, what that tells me, in how to kind of fix that, so what that tells me is, a little bit of a divot in this situation now, if I didn't have any high and dry grounds in that spent bed, in that bed, so that's what I'm talking about. When I'm talking about the bed, that's a bed of coffee. So if I didn't have any high and dry grounds, but I did have those divots, I would grind a little bit finer.

What those divots are suggesting to me is that there's not enough water above the bed of coffee as it's brewing the slurry of coffee grounds, and it's draining too quickly in, so the spray from the shower head, or from your pouring kettle if you were doing it manually, is churning up those grounds a little bit too much. And I could probably go a little bit finer. In that situation you go, but what if the extraction, let's just say the extraction wasn't over or under extracted. Well, in that situation, not exactly what I had, in the situation if you've got divots, but you have a flat bed and you don't have any high and dry grounds, you might also find, especially for a drip machine, a drip coffee maker, that it wouldn't just be a neat pattern. The bed would be kind of messy and all over the place, not nice and flat. Then what's going to happen is maybe it wasn't over or under extracted. However...

Pause due to poor connection. Sorry. Yeah, and paused again. We got a good connection yet? My God, this is driving me insane. Okay. Are we good? Are we good? No more pausing due to poor connection? I've got two of my little three wifi. Hopefully it's worked it out. No, keeps pausing, interrupting me. No? Okay. All right.

So that's the situation. What it tells me is I could grind finer. Now, if I didn't change anything else, that would be over extracted, but I could grind finer, get a more even extraction, which would be represented by a flatter bed without those divots, and then compensate by using cooler water or some other variable that I might be able to change in whatever situation I happened to be in. That would get me maybe the same level of extraction, probably a little bit higher, but sweeter with more origin character coming through for the coffee. It'd be my estimate.

Now the other thing we noticed, I'm going to pull it back again so everyone can see it again. The other thing we noticed was these, you can see on the wall here, what I mean by high and dry grounds is, it's got a bit of a convex shape. So it's not nice and flat. It's leaning up a little bit. It's a little bit hard to see on the camera, but you can see it there. Those grounds have gone up a little bit. So in that situation, it probably means that the water is building up too quickly, and so basically the flow rate was too high, or the grind was a little bit too fine.

So in that situation, where you've got the high and dry grounds, which is probably more often going to be the problem, particularly for a lot of people's pour over techniques and a lot of commercial drip brewers, home coffee makers, that's going to be the more common problem. In that situation, then I would want to grind a little bit coarser. That would lower the resistance in the bed, allow the water to drain a little bit faster, and as a result, I wouldn't get those grounds sticking up onto the wall, and same situation as what I just described. If you compensate with your other variables in order to get a similar kind of extraction level, it'll be sweeter with more origin character.

So this is what we're talking about. We're talking about the bed. So just tasting the coffee, it tastes really good. It's well extracted. So I'm pretty happy with that extraction level, but I know because my bed's not perfect. It's pretty good, right? So that's a pretty good place to start. I'm not too fussed about that one. I was hoping something a little bit more obvious to demonstrate with, but that's a pretty good bed. But by improving, by changing some of my variables, by improving the evenness of extraction, which would be represented in our spent grounds, our bed of coffee, then I could get a bit more origin character coming through in that brew, even at a similar extraction level. Or really, I could also extract a bit higher without getting astringency coming through, which will improve the sweetness and just overall enjoyment of the coffee, most likely.

You might even need to, if it was a big difference, if your pour overs were, the bed was really bad and you're making a huge change, I suggest checking out, if you're doing manual pour overs, opposed to drip brewing on this machine like I did, I suggest checking out the videos from Scott Rao and James Hoffman. They've got some really good instructional videos on how to brew a pour over well with a really nice flat bed at the end, get a really even extraction. If you are going to be able to get more even extraction and thus increase the extraction, then you might need to lower your dose a little bit.

Now, the things I was talking about just there, and the suggestions I made for changing the grind size, that's assuming the grind size are pretty much your only variable. Now, obviously if you're making a pour over, you can control your flow rate, and we'll talk about flow rate in a second when we go back to that brewer. But if you have a brewer like this pretty old school one, where basically it's just on or off, then grind size is pretty much your only variable. Now there is a little hack you can do where you can pour cold water into the brewer itself, and that will slow down the flow rate.

But on the Breville that I've got in front of me that I used this morning, you can control the flow rate. You can control the temperature, which means you're not relying on just your grind size to get an even and the correct extraction, not under or over extracted. So in this situation, if I had the ability to, what I would probably do is lower the flow rate a little bit, as opposed to grinding coarser.

This extraction is really good, and actually I know this, because yesterday I ground a bit coarser, and it was a bit under extracted. So I could lower the flow rate to try and reduce those high and dry grounds on the side of it, and probably get a more even extraction that way. However, I'm on the slowest setting on this brewer already. I can't lower the flow rate anymore. And because this brewer is controlling the flow rate, which is fantastic, controls the flow rate and temperature, means putting cold water in it probably won't change it because it's got a timer and it's got a pump.

So, if that bed was off of the old school kind of simple brewer I have over there, one we've been using for years, $60 job from Meyer, did a pretty good job. It needs a bit of management. Then what I would do is put cool water in it, as opposed to necessarily grinding coarser. For this one, what I'm probably going to do is grind coarser and increase the temperature. I'm going to grind coarser because I can't go a slower flow rate, and I want to get that bed a bit more flat, less high and dry grounds, more even extraction. But by grinding coarser, I'm going to lower the extraction, so I will increase my temperature to compensate.

So yeah, and there's always going to be a little bit of trial and error. I can't say increase temperature by one degree or two degree for however much I'm changing the grind. It's going to be a bit of trial and error. Hopefully we're in the ballpark. So those trials are still pretty delicious. Like that one, that's our roaster's blend. So I have no idea what's in that, but it's quite delicious. I think it's probably quite a lot of Colombian and Kenyan in there based on the taste, lots of black currant and brown sugar coming through.

This is meant to be a Tips and Tricks, but I have a question that came in, because I've done this live, so I will answer it. "What's your opinion on the Melodrip in relation to extraction and flow rate for manual brews?" Okay. So I'm going to say, I don't have a lot of experience with a Melodrip. For me, it's kind of counterintuitive a little bit. I want some agitation in that brew. So for those that aren't aware, the Melodrip is a device you can use when you're making manual pour overs, as opposed to an automatic device, like what I was talking about this morning. And it deliberately makes the drips mellow, hence the name. So it deliberately brews really gently.

In my opinion, it brews probably too gently. You could maybe compensate for that by stirring the slurry or spinning the slurry, something like that. But some agitation is good. You want some agitation in the brew so that all the coffee is extracting evenly. And without agitation, you're probably going to really struggle to get a nice flat bed. And I've found with a Melodrip that you end up getting kind of lower extractions. You could probably compensate for that. But yeah, I'm not a huge fan, but I know some people love them.

I think with anything, when it comes to equipment, whether it's a drip coffee maker, Aeropress, Melodrip, Hario versus Kalita for pour overs. With any of those things, I mean, one, experiment with different equipment. You might find some stuff you really like. But two, change your other variables. The equipment is just a static variable, and you've got your other variables you can play with. And I guarantee, for most equipment, you'll be able to find another combination of variables, whether it's agitation, temperature, grind size, whatever it might be, like water temperature, or grind size, you can find something that's going to work for that particular equipment and that device.

But yeah, so reiterating, this is a long one. I rambled a little bit because it was live, and I like doing these lives. Sorry. But yeah. So the tip for this week is to check your bed of spent grounds when making a drip coffee, so making a manual pour over or using a machine, and try and get that bed as flat as possible to get the most even extraction you can. It'll be the best way to maximize the sweetness and origin character in your filter coffee.

Thanks for tuning in, guys. We'll see you soon.