Chasing the Perfect Cup of Coffee with ScienceS

This coffee sucks. It's the second cup I've made in a row. It's sour and grassy. It should taste like red grapes and strawberry. I know exactly how bad it is, and I haven't even tasted it yet.

People accept scientific measurements as the truth about a lot of things. Mass. The temperature at which water freezes. The size of the earth. But it's hard to swallow the idea of scientifically measuring how something tastes. Taste is subjective. Right? Not anymore—thanks to ExtractMojo, a gadget that quantifies a cup of coffee's flavor.

***

Vincent Fedele created the original FireWire portable hard drive for PowerBooks over a decade ago. Steve Jobs held it onstage at a keynote. People applauded. Right now, Vince is telling me about how the FBI uses crappy imaging hardware to scan fingerprints at a mere 500ppi, so it's an astoundingly clumsy method of ID. He speaks at a rapid clip, his northeast accent twinged with the high-pitched nasality that immediately outs lifelong nerds. I can already tell I like him. His method—analyzing 1000ppi images with machine vision software designed to examine printed circuit boards—would make fingerprinting as reliable as DNA for identification. He wants to use it to make passports more secure. But the technological inadequacies of the federal government isn't why I called him.

Since selling his Mac peripherals company, VST Technologies to SmartDisk, Vince has turned his considerable expertise—in electrical engineering, physics, optics, materials science, digital communications and miniaturization, as he's relatively quick to tell you—to a different problem: shitty coffee.

Inevitably, the speciality coffee business—or what I call "progressive coffee," a tagline borrowed from Baltimore's Spro—is populated by obsessives. You might think it takes a certain kind of person to care that much about coffee, to not consider $75 for 12 ounces of beans an unreasonable extravagance, when most people wince at paying more than a buck for a cup of Joe. You're right. But it's these kind of people who craft anything that's really special. Insane pizza. The iPhone. Ferraris. Vince is that kind of person. I'm that kind of person. Well, I'm getting there, anyway.

The problem with coffee, Vince says, is that, even if it's sourced and roasted impeccably, "most of us blow it in the last 5 minutes." That's why he invented ExtractMojo and MojoToGo—to help us brew coffee right.

***

Before you can understand what ExtractMojo and MojoToGo actually do, you need to understand the Universal Brewing Control Chart and the Gold Cup Standard.

As Scott Rao's highly recommended book Everything But Espresso tells it, the original Coffee Brewing Control chart dates back to 1960s research by chemist Ernest E. Lockhart and the National Coffee Association. Through surveys, they determined how Americans liked their coffee brewed—specifically, the brew strength and flavor preferred by most people.

Chasing the Perfect Cup of Coffee with ScienceS

It's important to distinguish strength from flavor. You obviously know the difference between strong coffee that puts hair on your genitals and the seriously weak sauce that wouldn't make a 2-year-old twitch. Strong coffee has a lot of dissolved solids in it; the weak coffee, not so much. The ideal range, for most people, is a brew strength (or TDS) of 1.15-1.35 percent, according to Lockhart's original research. Today, depending on which coffee association you ask, the ideal range is between 1.2 and 1.55 percent. (The Europeans like it stronger, of course.)

Flavor is tied to the extraction. It's what you pull out of the coffee beans. When coffee is underextracted, it means that not enough of the flavor components are pulled out of the beans. The results tend to taste sour and/or grassy. When it's overextracted—when too many solids are pulled out—it tends to taste bitter. Properly extracted, if you're using decent coffee, it tastes sweet—maybe like red currants, plum and cranberry juice crowned with juniper and eucalyptus, if you're drinking Intelligentsia's Ethiopia Sidama Shilcho. That most excellent range of extraction is 18-22 percent. Less is underextracted. More is overextracted. You can have a strong cup of coffee that's underextracted, or weak that coffee that's overextracted. Starbucks serves just that, says Vince, "since they discovered you can use less coffee by grinding finer. They're using 20 percent less coffee, so they're extracting more," making it bitter.

The perfect cup of coffee has a brew strength (or TDS) of 1.15-1.50 percent and an extraction rate of 18-22 percent. It's a remarkably tiny spot to hit. But uh, how do you get there? If the brewing control chart is a map, ExtractMoJo and MoJoToGo are the GPS.

Chasing the Perfect Cup of Coffee with ScienceS

ExtractMoJo is, very simply, a refractometer paired with the universal brewing control chart, an updated version of the original chart from the 1960s. MoJoToGo repackages the ExtractMojo software into a superhandy iPhone app. The VST coffee refractometer is designed to measure coffee's concentration by measuring its refractive index. (It reads the speed of light through a liquid medium to around 5 decimal places). Not so long ago, a refractometer of the caliber would've cost around $10,000, says Vince, but thanks to the increasing power of digital camera resolutions, he was able to create a handheld model that's just a couple hundreds bucks.

When you plug the number the refractometer spits out, along with the amount of water and coffee grinds, into ExtractMojo or MoJoToGo, it tells you the brew strength and extraction yield. By plotting those on the chart, you know whether or not you've brewed a decent cup of coffee, and how sour, bitter, weak or strong it's going to be. By knowing exactly where your coffee lands, you have an idea of how to to get to the sweet spot, to the perfect cup of coffee.

The magic number, according to Vince, is a 19 percent extraction. It's a number that will haunt me.

***

Chasing the Perfect Cup of Coffee with ScienceSThe first cup of coffee I brew is a goddamn disaster, according to MoJoToGo. It's the first time I've used a press pot in a month. 16 percent extraction. I can tell it's underextracted before I even sip it; the moist grounds of Stumptown's El Salvador Kilimanjaro smell grassy, not like strawberry and red grape. My tastebuds confirm MoJoToGo's (and my nose's) prediction. I make it again, using a finer grind. 17 percent. Still way under. Shit.

Assuming you're using the correct dosages of coffee and water—which MoJoToGo will calculate for you, since precision is key—there are a couple of ways to increase extraction. Grinding the beans into finer particles produces more surface area for the water to come into contact with, resulting in more extraction. Making the water hotter increases extraction. So does increasing brew time. And agitation (read: stirring). I employ all of the above, one at a time. I tear through a $16.50 one-pound bag of coffee in about three days, making coffee over and over again, seeking the mythical number 19. I use a version of the French Press technique from Everything But Espresso. Start the kettle. Weigh the beans. Grind the beans. Wait for the water to reach 206 degrees. Pour 400g of the heated water onto the grounds. Start the timer. Pat the coffee bloom. Dunk the coffee bloom. Wait 4-5 minutes. Plunge. Pour. Check result in MoJoToGo. Curse.

The most frustrating part isn't the resulting Ahab-like hunt for the ever-elusive 19 percent. It's the revelation of how imprecise my methods are. The 18.3 percent cup that sends me into a delirious orbit before I even taste it is quickly followed by one that measures 16 percent (and tastes like it). I'm all over the map. It drives me insane. And to Amazon, to buy more precise equipment.

That's the dark side of MoJo, if there is one. Even in an industry that's driven by obsession—from the people who make coffee, and the people who drink it—Mojo can inspire a different kind of obsession. Spro owner Jay Caragay tells me about a dude who won't taste coffee without checking it on MoJoToGo first. "There's a place for MoJo," he says, but in the end, the only question that should matter is, "does it taste good?"

***

A week later, I'm making better coffee than I was before, more consistently. I still check every cup on MoJoToGo, every single time. But I can taste it too.