At the Denver Museum of Nature and Science, children and their parents meander through the Expedition Health exhibit, chattering about science and bodies, peering through microscopes and conducting experiments.
A set of glass doors abuts the exhibit, and every once in a while, after a quick chat with a museum volunteer, a family makes its way through the doors.
Today, that family is the Bacas -- Tim, and daughters Raveania and Desiree, ages 12 and 11, from Aurora. They sit at a tall lab bench, and listen as Anjelica Miranda, dressed in a white lab coat, guides them through a taste test.
The Bacas are not aware of it yet, but they are taking part in one of the most unique science experiments in the country. Their taste test results, combined with that of hundreds of other museum visitors, may help scientists discover the genetic underpinnings of a sixth taste.
"Let's go ahead and put our nose clips on, when you're ready," said Miranda. "Do a quick sniff test, make sure you can't smell."
The Bacas are about to place a flavor strip on their tongues. It looks a little like a breath mint strip, translucent and plastic in texture, but this version is coated with a specific taste molecule.
Miranda sets the timer for 45 seconds, as the they let the strips dissolve on their tongues, 11-year-old Desiree scrunches up her face. The taste is not exactly pleasant.
That's because the strip contains linoleic acid, a fatty acid that's a part of foods like nuts, oils and seeds. By itself, it's not exactly flavorful. Raveania Baca's description is pretty spot on.
"You know how you smell cardboard boxes? I tasted that in my mouth."
The ability to taste that cardboard box, though, just may indicate the existence of a sixth taste: fat.
Most Americans have probably only heard of four tastes: sweet, salty, bitter and sour. There's actually five known to science -- the fifth one, umami, the savory taste of broth and cooked mushrooms, was discovered by the Japanese in the 1900s, but only recognized by American researchers more recently.
"There's a lot of different questions that have to be answered for the field to say, yes, you know what, we're letting fatty acid into the club. And we're not quite there yet."
That may be why most Americans haven't heard of it, said Robin Tucker, a taste scientist at Bowling Green State University, in Bowling Green, Ohio who is analyzing all the data collected in Denver.
"So we sort of kept pushing the envelope to see what else we could find that we were able to taste, and we came across the idea that we could actually taste fat," said Tucker.
Other than the thrill of discovery, this knowledge could have important health implications.
Say one group of people is more genetically predisposed to taste fatty acids. That might affect what kinds of foods they choose to eat, and "that might affect your diet, your weight, your body fat percentage, some of these known risk factors that put you at risk for chronic disease later on," said Tucker.
Back in the lab, the Bacas are finishing up another taste test, one of several they do over the course of the experiment. The stopwatch beeps.
"So with your nose clips still on, go ahead and rate the intensity of the strip," said Miranda.
They mark their results on a sheet of paper. The taste test is random, so each family member could have had a different strip or a strip with a different intensity of flavor.
Then Miranda tells them to take off the nose clips.
"Outstanding, that smell kicks that taste in so intensely," said Tim Baca.
The nose clips help isolate the taste from the flavor, explained Miranda.
"So smell is a really, really big component of flavor. Taste is just the five tastes that we described, but flavor is everything else like smell, sight, what it looks like, what it sounds like, what the texture is," she said.
Miranda's joint role as educator and experiment-runner is by design, said Nicole Garneau, a geneticist who chairs the museum's health sciences department.
"We are really trying to break down the barriers of accessibility to show that you don't have to be a trained scientist to understand science. It's for you, by you."
The "by you" part is double-layered: Miranda, who sounds as expert as any scientist when running the experiment, is actually a volunteer, one of nearly 50 at the museum who run the experiment with the public seven days a week.
These citizen scientists, as the museum calls them, receive a monthslong intensive training on lab techniques, educational skills, and human subjects research. The volunteers running the experiment range from college-age (Miranda is a student studying immunology) to retirees in their 80s. Some have science backgrounds, many do not, said Garneau.
Without volunteers, the experiment wouldn't be possible. The Bacas were participants 824, 825, and 826. By the time the experiment is over, over 1,200 people will have been through the museum's lab. This gives Bowling Green State University's Tucker access to a population she would never otherwise have found.
"I worked on this project for my dissertation for four years and I tested fewer than 100 people. And at the museum they've tested over 700 people in just under a year and a half," she said.
Tom Finger, a taste scientist at the University of Colorado at the Anschutz Medical Campus, has followed the museum's work. He said the scale of the experiment allows for much better analysis.
The population is also a lot more diverse than those found on the typical college campus, said Finger.
"They'll enroll thousands of subjects whereas previous studies would have 100 subjects at most," he said. "So they get a much better statistical analysis of their data and they can see small factors in the data that would be missed by smaller studies."
Garneau said while this experiment may not convince everyone in her field that fat is the sixth taste, it is a strong step in that direction.
"It's kind of a funny club that is hard to break into," she said.
"There's a lot of different questions that have to be answered for the field to say, yes, you know what, we're letting fatty acid into the club. And we're not quite there yet. But there's a lot of great evidence that gets us pretty darn close."
