Home-Brewing 101: Understanding Extraction and Strength

Every time we brew coffee, we’re using water to extract soluble material- i.e. materials that are able to be dissolved- from our coffee beans. Swirling around in your morning joe is a complex solution made up of plant cellulose, lipids, minerals, acids, caffeine, proteins and sugars. You can thank these materials for giving your coffee its flavor. Yum!

Well, it’s mostly “yum”: only about 30% of the coffee bean is dissolvable, and only 18-22% of it even tastes good. The math doesn’t really seem to be in our favor, does it?

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Because not all of coffee’s flavors are palatable, we need to control the amount of soluble materials that dissolve into our water when we’re brewing. Many variables come into play here, but ultimately one of three things is bound to happen when you make coffee: it’s either going to end up over, under or well extracted.

When more than 25% of the materials in the bean have been extracted, it’s considered to be over-extracted. Coffees that are over-extracted taste bitter and astringent. Think: bad shivers, a mouth-drying finish and the need for something to wash the bitter taste out of your mouth. You know what I’m talking about. Yuck.

When less than 17% of the materials have been extracted, the coffee is considered to be under-extracted. Under-extracted coffees tend to taste sour and a little salty. They hit you first thing, at the front of your palate. They’re a real (coffee)buzz kill. #dadjoke

It’s important to understand the difference between a coffee that is acidic and bright because of its naturally-occurring flavors,and a coffee that is sour because of under-extraction and/or under-development. Coffee beans are the seed of the coffee fruit so fruity flavors are bound to happen. Coffees do, in fact, occasionally taste fruity, bright and/or tart. That’s totally fine,and even preferable (depending on your palate, of course)! But if you’re tasting weird vegetal notes, puckering your mouth at the sourness and experiencing a hollow, unbalanced finish, you’re in under-extracted territory. Get outta there.

A well-extracted cup of coffee tastes sweet, complex and balanced. You can taste distinctive flavor notes- blueberries! Lemon! Tomato! Oh my! When a coffee is extracted properly, it’s pleasantly acidic. It has a lingering, enjoyable finish that leaves you savoring flavors long after you’re done with the cup. A well-brewed coffee is a beautiful thing to behold.

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Strength

“Strength” has to do with the amount of materials dissolved, or the total dissolved solids (TDS), in your final brew. Please note: the strength of a coffee does not refer to its caffeine content or roast level. “Strength” is not a subjective term and can be measured on a refractometer using science, light and witchcraft (technology). It’s a pretty amazing device and if you’re ever able to mess around with one, I highly recommend it. Be sure to wear a lab coat for the full effect. It’s great.

A lil’ note from a comment by one of my favorite coffee nerds, Brady Butler, who serves as Chair of the Brewing Pathway Committee for the Specialty Coffee Association of America: “I’ll break out that white lab coat for a second… Your properly-extracted 1:16 pour-over is gonna be about 1.4% dissolved coffee solids, 98.6% water. For reference, lots of places brew a far weaker cup, often less than 1% solids. The range for Golden Cup is 1.15-1.35%.” (Thanks, Brady!)

One of the major determining factors in the strength of a brewed coffee is the ratio of coffee to water. This is where a good scale comes into play: it’s vital to be able to measure both your input (dry coffee grounds) and your output (water) so that you can control your ratios precisely. Brewing coffee without a scale is like trying to bake a cake without measuring cups. You wouldn’t just grab a fistful of flour and think that it was an accurate measurement, correct? The same applies with coffee. When you’re brewing coffee, I encourage you to think of it as a cooking experiment. Find a good base recipe, get the best ingredients you can, use the proper tools, and then adjust to your taste.

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Different brewing methods have different ideal ranges of coffee-to-water ratios. For pour-over coffees, I’ve found that 1:16 is a good place to start. A French-Pressed coffee usually tastes best for me somewhere around a 1:10 ratio. And most Aeropressed coffees are tasty for me at approximately 1:12. (infomercial voice) BUT DON’T TAKE MY WORD FOR IT! Do some research and personal experimenting to determine what’s best for your methods, palate and preferences.

Nerd alert: I keep a notebook in my kitchen to record my coffee experiments. When I’m playing around with a new brewing method I’ll jot down my variables (water temperature, ratios, brew time, etc.) and the outcome of the coffee. I’ll do this over and over until I find a recipe that I like. And even when I find one that I like, I’ll just keep tweaking things until I find something that I love! Keeping a record of my coffee successes and failures has helped me brew more consistently good coffee in the long run.

Your coffee-to-water ratio is only one piece of the puzzle. You can have a good base recipe and still end up under- or over-extracting your coffee by brewing with water that’s the wrong temperature, timing your brew improperly, grinding your coffee weird, and so on. But don’t fret! We’ll be covering all of our bases over the coming weeks. In my next “Brew School” post, I’ll explain how and why particle (grind) size and brew time matter. Stay tuned.

For now just watch this video and enjoy. Gets me every time.

(photos by Joshua Vasko)

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