Measuring Flavor Extraction for the Perfect Cup of Coffee

By Wesley Fenlon

The Atlantic lays out the science and methodology of coffee.

As we've shown in the past, your coffee brewing method of choice--be it the Able Kone or the Aeropress or another piece of technology--has a direct impact on how your coffee turns out. But brewing the coffee is the last step, and everything before that is important, too. The kind of coffee you buy. The way you grind it. The temperature of the water. And, of course, the ratio of coffee to water; it all matters, and even the perfect Aeropress brew could come out bitter and foul without the proper process.

The Atlantic recently published a thorough, fairly beginner-friendly guide to making the perfect cup of coffee. It mostly focuses on the process leading up to brewing, leaving that final method up to you. The guide starts with the "golden ratio," which is meant to supply the perfect combination of water and coffee grinds for a perfect cup. And this is perfection as judged by the masses--it's based on studies from the Specialty Coffee Association of America.

"The key is to start with the Golden Ratio of 17.42 units of water to 1 unit of coffee," says the guide. "The ratio will get you into that optimal zone, plus it is unit-less, which means you can use grams, ounces, pounds, stones, even tons if that's your thing."

There are two key terms to know here if you're ready to get scientific about your coffee: Percentage Extraction and Percentage of Total Dissolved Solids. The guide elaborates: "The Percentage Extraction is the amount of coffee particles extracted from the original dry grounds. The Percentage of Total Dissolved Solids is the percentage of coffee solids actually in your cup of coffee (commonly known as 'brew strength'). When you correlate these, the result is a Coffee Brewing Control Chart, with a target area in the center that highlights the optimal brew strength and extraction percentage."

Some fancy technology comes into play when you get into measuring Total Dissolved Solids: a refractometer, to be specific. Pairing that refractometer with a piece of software called ExtractMoJo allows you to measure the extraction of solids from your coffee grounds. According to the Brewing Control Chart mentioned above, perfection sits between 18 and 22 percent. That's where optimal flavor lies.

Getting that flavor, it turns out, is simple as the right ratio of water, a refractometer, and a $150 piece of software. Actually, it's not that simple--you'll need a good coffee grinder, good coffee beans, water between 195 and 202 degrees Fahrenheit, and a whole lot of practice with your chosen brewing method. But at least The Atlantic's guide makes it all a little bit easier.