Extraction and Strength - The Basics to Brewing Coffee
So you’re trying to dial in your brew. You’re getting a great cup of coffee, but perhaps you’ve had better and would like to improve it. I’d like to simplify coffee brewing down to the basics by discussing two metrics, extraction and strength, and discuss how they work together to produce flavor.
In coffee, we have two spectrums, and we’re trying find a balance between the extremes on each side of each spectrum. Striking the sweet spot in brewing for a particular coffee is the goal, and what should result is something with nice body, juicy mouthfeel, and pleasant flavors that vary from coffee to coffee. So let’s get into each one.
Coffee extraction is when solids within the structure of the coffee grounds are separated by water. Water either pours over, pushes through, or immerses coffee grounds. As the water contacts the molecular parts of the grounds, it grabs soluble solids and stores them within itself. The coffee solids are dissolved in the water, changing the flavor and the body of the water. This is the chemistry of brewing coffee. If with the water you extract too much, you’ll taste very bitter flavors in the cup. If you extract too little, you’ll get sour notes. Find a good balance, and you’ll taste pleasant sweetness, good body, and a juicy mouthfeel.
Coffee strength is quite simply the ratio of the extracted coffee solids over the water. The more coffee solids in a cup, the stronger it is. This is perceived pretty easily, even by coffee novices. The more it tastes like water, the weaker it is, and the more it tastes like coffee, the stronger it is. Espresso is very strong coffee, while drip coffee is much weaker.
Managing Extraction and Strength
Coffee extraction and strength correspond to one another. They are controlled by 3 basic variables and a few other minor variables. The 3 basic variables that control extraction and strength are dose, yield, and time. The last of these can be manipulated with grind level if you’re using the espresso or pour-over methods. If you’re using a French Press or any other immersion brewing method, you’ll need to add grind level to the list as a separate basic variable. If you can manage the basic variables and get some excellent coffee, then you can fine-tune your brew with water temperature, managing the TDS of your water, or by using some other method-specific tricks.
First, and most importantly, is the dose. How much coffee are you going to use? This is very method-specific as well as equipment specific. Espresso machines, for example, come with portafilters from the manufacturer with baskets that hold a specific amount of coffee. A Hario V60 or a Chemex is designed to hold a certain amount of coffee. A lot of these have manufacturers recommendations for dose size. For coffee, I recommend that you use metric. It’s much more precise and convenient than standard. For the pour-over and french press methods, the golden ratio is 55 grams per liter of water. So sometimes you work backwards from the capacity of your carafe or container and fit it into the golden ratio. However, consider this step one, so if you need to change the dose size further down the line, you need to start all the way over.
Chemex scenario: I used the 10-cup Chemex for the first time ever just recently. I had no idea where to start, and there were tons of variables up in the air. My first step was to nail the dose down, but I didn’t know how much it was supposed to yield. Of course, it says 10-cup, but if you’re familiar at all with the way cups are used with coffee gear, you know that it’s a pretty useless number. So the first thing I did was figure out the actual volume of the container below, about 1.2L. Using 55g/L, I flexed some of my algebra muscle and determined that I needed 66g of coffee to yield 1.2L. At this point, I lock the 66g.
Next you determine the yield you’re trying to achieve. As mentioned above, for filter and immersion methods, the golden ratio is 55g/L. Use the dose that you’ve decided to nail down in the previous step, and solve for the yield you’re aiming for. Water conveniently weighs about 1000g/L. So when you’re ready to brew, just tare your scale, and add the amount of water in grams that corresponds to your volume.
Chemex scenario: Since I worked backwards, I already have the yield I’m aiming for. So I lock that in at 1.2L or 1200 grams.
Finally, you need to determine a time that you’d like to aim for. For espresso, industry standard is between 25 and 40 seconds. So just choose one and roll with it. For drip coffee and french press, 4 minutes is a good starting point. Aeropress is normally around 1 minute. So choose a time that makes you feel right, and go for it. To control this with espresso or drip coffee, you manage the grind level. If you’re doing this for the first time, you grind a little coffee and rub it between your fingers, feeling the coarseness or fineness. French press needs to be pretty coarse, espresso is very fine, and drip coffee should be a medium. So again, just make your best guess, and time your brew.
Chemex scenario: Since the standard drip coffee time should be around 4 minutes, that was my aim. So my final recipe was 66g of coffee, 1200g of water, for a 4 minute total brew time. I thought at first that a particular grind level on my grinder would get me there, but I was way off and got a 10 minute brew time (bitter and dry, see below). I ground much more coarse the second time around and achieved a must quicker brew that tasted excellent.
This is how you craft a brew recipe. The aim here is to extract the right amount of coffee solids for a great tasting cup. Below you’ll see how to dial-in your brew by tasting and managing the levels above.
Execute your recipe, and taste the coffee. Gauging extraction and strength, what I call macro-tasting is actually very easy. Micro-tasting, or perceiving the origin notes of a coffee, such as the big categories of fruits, florals, or spices, is much more difficult in relation. In fact, getting a good balance of extraction and strength is crucial to micro-tasting. The negative flavors that result from poor extraction with veil the origin flavors and make them imperceptible. So let’s diagnose poor extraction and fix it!
Over-extracted and Weak
This is probably the most common problem because people try too hard to be budget-conscious. The coffee in this cup is both thin, bitter, and dry. Extending the brew time by grinding finer might strengthen the brew, but it will extract even more which will result in a cup that’s even more bitter and dry. The solution here is to either increase your dose or decrease your yield.
Under-extracted and Strong
This is more common in espresso, but it can be achieved with other brew methods. This is pretty unpleasant because not only is it way too intense, it’s intensely sour. No one wants lemony tartness in their cup of coffee. This is due to two problems, too high of a dose (or too low of a yield) and too coarse of a grind. Decrease the dose or increase the yield, and grind finer.
Under-extracted and Weak
This is another one that’s more common with espresso, and some of that is due to a weak tamp. For espresso, this will rush out of the portafilter and you’ll get like a 10 second shot. You get a ton of coffee, and it tastes weak and sour. For filter coffee, this brew goes way too quick, and in a matter of like 2 minutes, you’re out of water. The flavor is weak, and it feels thin. You may be able to taste lemony sour notes, but they’ll be hard to discern because of the weakness. The problem with either espresso or filter coffee is that the grind level is too coarse. Grind much finer, and extend the time of the brew.
Over-extracted and Strong
This is due to a good dose, good yield, and lengthy brew time. The espresso shot took a full minute, or your pour-over took 10 minutes. The result is very obviously bitter and dry, easy. The grind is too fine, and the water is having a tough time getting all the way through the grinds. So grind more coarse, and shorten your brew time.
You are now well on your way to great coffee. This is truly the Pareto principle at work. 20% of your labor yields 80% of the quality. Nail these coffee basics, then you can use the other, more complicated variables to fine tune your brew. If, after you’ve pulled all your hair out trying to get your extraction just right and you’re still not getting a desirable cup, perhaps you’re using poor quality coffee. Be sure you check out our shop and get yourself some coffee that’s fresh and craft-roasted!
To access the new SCA flavor wheel, check it out here: SCA Flavor Wheel