Barista Magazine

AUG-SEP 2019

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A s c i e n t i f i c a p p r o a c h T a s t i n g p a r a m e t e r s S e t t i n g t h e s t a g e T h e r e s u l t s 94 barista magazine ROUND THE WORLD, coffee professionals argue the merits of various pourover brewers: Hario V60 versus Chemex versus Kalita Waves versus Clever Drippers, and so on. Some believe that different roasts work better in different brewers. Some alter their brewer depending on the fl avor profi le they're trying to achieve. But everyone agrees on this: The brewer impacts the coffee's taste. The theories abound: The fi lter is a big factor. Chemex paper fi lters, for instance, are noticeably thicker than most other fi lters. The thicker paper fi lter holds back more of coffee's oils and creates a thinner mouthfeel in the cup. Filter material matters, too: Bleached white fi lters might also allow for a "cleaner"-tasting cup, or they might impart a papery taste if they're not rinsed before brewing. Similarly, natural bamboo fi lters can impart a woody fl avor to coffee. And metal fi lters? Those don't hold back much oil at all, so coffee brewed with a metal fi lter often has a distinctly thicker mouthfeel. The walls of the brewer are another source of deviation in brew results. Here's the rub: Water is lazy, and it will take the path of least resistance, so space between a paper fi lter and the wall of the brewer creates room for water to move through, like a shortcut. Instead of mov- ing directly down through the bed of coffee, water can move through that empty space, skipping the coffee bed all together. Unlike most other pourover methods, the Chemex features a solid glass wall, which slows down water's fl ow. That's why 4–5 minutes isn't an unreasonable brew time on a Chemex but is considered long when using other brewers. Grooves in a brewer dictate the direction the water moves and speed up water's fl ow by holding the fi lter away from the walls. Each brewer's grooves are unique. All these factors—and so many more!—allow baristas to defend which brewer they think is better. But is there a way to know which brewer is better? The scientifi c community is working on it. At the University of California at Davis, Dr. Scott Frost, Professor Jean-Xavier Guinard, and Professor William Ristenpart conducted a study isolating one of these factors: brew basket shape. They compared a cone-shaped brewer like the Hario V60 to a fl at-bottom brewer like the Kalita Wave to try to answer that hotly debated question: Which shape delivers a better brewed coffee? A scientific approach UC Davis has a long history of fl avor science. Rose Marie Pangborn joined the UC Davis Department of Food Technology in 1955, where she was a pioneer of sensory analysis—that is, studying something based on our senses. When baristas analyze a coffee's fl avor during dial-in today, they're upholding her legacy. However, it wasn't until 2013 that UC Davis opened its Coffee Center, an interdisciplinary institute where professors from engineering, food science, agriculture, chemistry, genetics, and more come together to research coffee. There hasn't been much sensory analysis of coffee at UC Davis since the 1970s, however This recent experiment with brewer shapes was like a warm-up, a fi rst step back into Rose Marie Pangborn's tradition of analyzing coffee using what matters most: what we taste. I spoke with Dr. Scott Frost, who recently fi nished his post-doctoral research at UC Davis and is now studying wine in Washington state. (Lucky!) He was the one in the lab with the panelists tasting the coffee. For the rounds of taste testing, Dr. Frost used two different coffees. One was a light-roasted Colombian from Peet's Coffee. The other was a dark-roasted blend from Starbucks. These two coffees remained consis- tent throughout the experiment. The actual devices used were the Breville Precision brewers, which feature an interchangeable cone or fl at basket to hold the ground coffee during brewing. This unique brewer allowed the team to make sure that everything in the experiment remained the same except the shape of the basket. The water was the same every time, as was the temperature used for brew. Dr. Frost made each cup "to order." Tasting parameters The fi rst step of this experiment was to make sure that it was even possi- ble to taste a difference between fl at-bed and cone-bed brewers. Anec- dotes from professional baristas are one thing, but would normal people be able to identify which coffee came from which brewer? To fi nd out, the researchers brought in 45 tasters for several triangulation exercises. In triangulation tasters are given three coffees at a time, two that are the same and one that's different. They're asked to pick the odd coffee out. If you're thinking this sounds like World Coffee Events' Cup Tasters Championship, you're not wrong. This tasting setup, however, is much more intense. The rounds of triangulation used several combinations of the two coffees ground at two grind sizes and brewed using the two basket shapes. A single round of triangulation could have looked like two cups of the light single-origin ground fi ne and brewed with the cone, next to one cup of the same coffee ground coarse and brewed with the cone. Dr. Frost would systematically switch out one variable at a time and ask the tasters to identify the odd coffee out. Setting the stage The 45 tasters recruited were non-experts, all students and teachers from UC Davis. Some of them had taken Professor Ristenpart's introduc- tory Design of Coffee class. They were isolated into booths so they could be served without any sort of bias from their surroundings. Bias is tricky to truly eliminate because we often don't recognize from where we're actually getting it. But it shows up in moments like when we see two coffees next to each other and assume that the one that looks darker in the cup is also the darker roast. The human brain loves patterns, so we look for them everywhere. This can turn into bias because we tend to want confi rmation of our own assumptions. Bias is the process of—con- sciously or unconsciously—looking for things that support whatever we already believe. Eliminating bias is an elaborate process that has to consider every single angle. For this experiment, Dr. Frost served the coffee in white porcelain mugs that were exactly half full. The tasting booths were fi xed with red lights so tasters couldn't easily discern a difference in the visual darkness of the coffees in the mugs. Each cup had to be served at the exact same temperature—65º Celsius/149º Fahrenheit—or they ran the risk of the taster detecting a subtle temperature difference rather than an actual fl avor difference. (Dr. Frost actually stood outside each booth and measured each cup with a thermometer. He only allowed tasters access to the coffee when the brew was the exact right temperature.) Had any of the coffee service subtly indicated the coffees were different, the entire taste experiment would be invalid. Anyone who's competed in a triangulation cup-tasting competition knows the power of guessing—if you can't identify the different cup, you've got a 1-in-3 chance of guessing right. That probability extends here: In this experiment the UC Davis team expected a third of the panelists, or 15 of the 45, to simply guess correctly. To make sure this test represented a true difference and not just lucky guesses, the scientists were looking for way more than 15 tasters to consistently name the odd coffee out. The results In this fi rst experiment with eight triangulations, the organizers found that yes, there's a taste difference between coffee made on cone- and fl at-bot- tom brewers. Twenty-fi ve of the 45 non-expert tasters could consistently

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