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How to make espresso with taste and sustainability in mind

For the longest time, I was sharing a coffeemaker with my roommate. But when I moved into my partner's place a few months ago, I ended up having to learn how to use his espresso machine. Initially, I was resentful: Why did my partner have to be so fancy? Unlike with a cup of coffee, a bunch of factors influence the quality of an espresso shot, leaving little room for error. After a month of pulling terrible shots, I’ve finally optimized my process enough that I can pull a thick, flavorful shot around 80% of the time. Now, researchers have purportedly uncovered the secret to consistently making espresso that not only tastes good, but also results in fewer wasted coffee grounds, CNN reports.

First, though, some background on how an espresso machine works: Making a shot of espresso involves packing coffee grounds into a receptacle called a portafilter and forcing hot, pressurized water through them. The fineness of the coffee grounds, how densely you pack them into the portafilter, and the water pressure can all influence the shot you pull. For example, grinding the beans too finely or packing them too densely can prevent the water from flowing through, clogging the portafilter and resulting in a few feeble, sludgy drops.

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To brew espresso, cafes typically grind a hefty quantity of beans, or about 0.7 ounces, as finely as possible, CNN reports. This exposes a greater surface area of the grounds to water, maximizing the extraction yield, which refers to the proportion of the grounds that gets pulled into the shot.

But the researchers who conducted the new study, published in the journal Matter, found that this method blocked up the portafilter, lowering extraction yield and leading to inconsistent flavors from one shot to the next. A ton of coffee grounds were wasted, too, a concern amid climate change, which may make some coffee species go extinct.

The researchers used a mathematical model to conclude that consistently pulling the same extraction yield is a matter of using a coarse grounds and less coffee. Using less coffee creates extra room for the water to flow through the portafilter, allowing it brew more of the coffee — meaning that 15 grams of coarse grounds can result in a shot with the same caffeine boost as a standard 20-gram shot, and the same extraction yield, every time.

These shots would also take less time to pull, since the coarse grounds allow more room for the water to flow through. Implementing the findings at an Oregon cafe resulted in cost savings and faster service. It also made their lighter roast taste better, VICE reports.

But the findings come with a major caveat: Consistent extraction yield doesn’t necessarily translate to a good shot of espresso. The standard process — using a high volume of fine grounds — obstructs water flow through the grounds, which actually produces more complex flavors. The drawback, of course, is that not every shot will taste the same.

Personally, I love the rich, almost syrupy espresso that results from hot water struggling through finely-ground coffee, and the mini rush of accomplishment it brings — even if that means I mess up every now and then. Some things you just can’t narrow down to a formula.