How Coffee Brewing Methods Affect Flavor with Jamie Smith, R&D

YOU BREW YOU: THE SCIENCE OF BREWING METHODS & FLAVOR
Brewing methods typically fall into three main categories: pour over, immersion, and espresso. Each one introduces water to coffee in a different way and for varying lengths of time, which has a huge impact on flavor. How huge? Let’s get into it.

PERCOLATE ON THIS 
If you’re a daily at-home brewer, you might already know about pour over: a brewing method that involves gently pouring water in stages on a bed of ground coffee over the course of a few minutes. The water flows through the grounds and filter, collecting just-brewed coffee in your vessel. This hands-on method allows you to control the flow and extraction rates (extraction is the process of pulling soluble compounds from coffee grounds … more on that below) for a tailored cup of coffee. If you want to geek out a bit—and we think you might, fellow Peetnik—this movement of water through a porous substance is also known as known as percolation. 

PERCOLATION, THE SEQUEL
Now you might be wondering: if that’s the definition of percolation, then what is my drip machine doing? It’s the same (really!)—it’s just automated. With pour over, you heat your water and rinse the paper filter, add your grounds, grab your hot water again and start to pour over—hey, that’s the name!—the coffee grounds, and so on (you know the drill if you’ve read our brew guides). With an automatic drip machine, you add water, a paper filter, and grounds before pressing START, which makes the heating elements kick in and water flow through the grounds. With a drip machine, you trade a little bit of control for consistency—so, maybe you can’t change the water temperature or its distribution over the grounds, but you get great reliability and convenience.

NEXT, DIVE INTO IMMERSION BREWING
In contrast to percolation is the French press—a brewing process that uses full immersion. You add all the water at once, piping hot, and let the coffee steep for several minutes. Then you press—hey, that’s the name! again!—the plunger down to separate the grounds from the brewed coffee. With no paper filter and a long steep, the immersion-style French press (aka coffee press, press pot, coffee plunger, or cafetière if you’re fancy) is notably different from the percolation method. 

LAST BUT NOT LEAST: ESPRESSO
Ah, espresso. The essence of your daily latte. In this method, a machine quickly forces pressurized hot water through fine-ground, densely packed coffee to create a concentrated, viscous, and flavorful extraction. Technically, you could call this a type of percolation. But because of the force used to push water through the grounds, and the difference in the final product, most Coffee People (hi) would consider it its own method.

SO, WHAT DOES ALL THIS MEAN FOR YOUR CUP? 
Lots! Let’s focus on percolation and immersion, the methods for making a classic, 12-ounce cup of black coffee. In a percolation brew—whether pour over or drip—extraction happens quickly as water flows through the grounds. This is in contrast to immersion brewing, in which the coffee steeps slowly, allowing the extraction to build over time and become more concentrated (not unlike how we extract tea). This rate of extraction plays one of the biggest roles in shaping the flavor of your cup.

WHY? BECAUSE … SCIENCE! 
Coffee contains over 1,000 flavor compounds (for comparison, wine has about 800, a fact we coffee sensory nerds love to brag about). But here’s the catch: only about 30% of a coffee bean is actually water-soluble, and only 15–20% of those solubles taste good. Lucky for us, many of the most desirable flavor-active compounds in coffee extract early. 

HERE’S WHY IT MATTERS
Broadly speaking, caffeine and a range of organic acids come out first, followed by heavier compounds: lipids, fats, and so on. Those lipids and fats do a lot of the work when it comes to body and texture. That’s why immersion methods tend to have a round taste and a full mouth feel: the grounds sit in water longer than the other brewing methods, giving more time for oils to dissolve into the brew. With pour over, there’s a shorter contact time between grounds and water, and a paper filter traps many of the oils for a lighter cup, which is often referred to as a “cleaner” cup, as it does not contain the breadth of oils and compounds. Not necessarily good or bad, just a matter of taste.

SO, WHICH METHOD’S RIGHT FOR YOU?
One of my favorite things to do when introducing coffee lovers to the wild world of brewing is to have them brew the same coffee using different methods. If you were to brew our all-time best seller, Major Dickason’s Blend®, using pour over or drip coffee maker, a French press, and an espresso machine (if your home set-up is tricked out like that), you’d be surprised at just how varied the body and texture, and even the tasting notes, can be. Coffees still surprise me, like this August’s limited release, Ethiopia Refisa Station. Using pour over, Refisa Station revealed delicate florals and sweetness, with notes of tangerine and oolong tea, plus a soft mouthfeel. In the French press, it became a creamy, full-bodied cup with pronounced cocoa and stone fruit. And as an espresso, it was plush on the palate with lots of complexity and stone fruit notes, and it would likely pair nicely with oat or almond milk. Sometimes you just don’t know until you try.

WE MADE IT! THE CONCLUSION
Coffee is full of surprises (and science!), and that’s exactly what makes brewing it such an exciting and endlessly rewarding experience. There’s a whole world of chemistry behind why your coffee tastes the way it does, and we’ve only just scratched the surface. But at the end of the day, I always encourage you, dear caffeinated reader, to play around with different brewing methods and see which flavors and compounds speak to you most. Are you a lipid-loving, full-bodied kind of coffee drinker? Or do you lean toward brighter acidity and a softer mouthfeel? As for me, it all depends on the coffee. But we’ll save that conversation for another time.

- Author Jamie Smith is Peet’s R&D Manager and all-around coffee superstar