Log cfu/ml of bacteria recovered from sterile water in which crackers had been dipped 3 or 6 times, discarded after each dip, with or without being bitten before dipping. Credit: Data courtesy of Paul Dawson Who hasn't in" /> Log cfu/ml of bacteria recovered from sterile water in which crackers had been dipped 3 or 6 times, discarded after each dip, with or without being bitten before dipping. Credit: Data courtesy of Paul Dawson Who hasn't in" />
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Doctor double dip

Log cfu/ml of bacteria recovered from sterile water in which crackers had been dipped 3 or 6 times, discarded after each dip, with or without being bitten before dipping. Credit: Data courtesy of Paul Dawson" />Log cfu/ml of bacteria recovered from sterile water in which crackers had been dipped 3 or 6 times, discarded after each dip, with or without being bitten before dipping. Credit: Data courtesy of Paul Dawson Who hasn't in

By | April 1, 2008

<figcaption>Log cfu/ml of bacteria recovered from sterile water in which
            crackers had been dipped 3 or 6 times, discarded after each dip, with or without
            being bitten before dipping. Credit: Data courtesy of Paul Dawson</figcaption>
Log cfu/ml of bacteria recovered from sterile water in which crackers had been dipped 3 or 6 times, discarded after each dip, with or without being bitten before dipping. Credit: Data courtesy of Paul Dawson

Who hasn't invoked the five second rule? After all, food that falls to the kitchen floor is still safe to eat, if you pick it up fast enough. Isn't it?

Paul Dawson, of Clemson University's food science program, roots out the science behind such questions and in doing so has found a way to engage undergraduate students, teach them the rigors of scientific investigation, and even encourage some to seek advanced degrees in the sciences. His formula is simple: Test the logic - or lack thereof - behind pop culture myths or stories. He started with the five second rule: if you drop a piece of food on the floor then pick it up in less than five seconds, it's safe to eat. Dawson's study set the popular wisdom on its ear. No matter how quickly the dropped morsel is retrieved, it's crawling with all kinds of bacteria.

After debunking the five second rule, Dawson and his students turned their sights on a popular Seinfeld episode wherein George Costanza double dips a chip, is caught at it, and an argument ensues about proper dipping etiquette. "I honestly didn't expect to find that much bacteria from the introduction of a single chip," Dawson says. Dawson designed an experiment where students simulated Costanza's double dipping by dunking a snack cracker into sterile water several times either with or without biting from the cracker between dips.

What Dawson and his students discovered - that double dipping increases the number of bacteria in a shared bowl by about three times - surprised everyone, so much so that The New York Times covered the story. Dawson's dean warned him: "Clear your calendar." More press coverage followed, and Dawson plans to capitalize on the attention by testing other popular myths. "I now have a whole list of things to investigate."

The next myth up for testing is related to the five second myth: "There are people who think that if you pick the food up off the floor and blow on it, you'll blow off any harmful bacteria," Dawson says. "To the contrary, what you're doing is introducing more bacteria and we're going to prove that." He laughs and continues, "We might take the food to the wind tunnel here and see just how much wind it takes to remove harmful bacteria."

After that, Dawson and his students will move on to the Chinese custom of using chopsticks to remove food from communal bowls to see how much bacteria is introduced from each dip of the chopsticks. Dawson's doctor has even suggested investigating the bacterial count in Communion wine. "I'm a little hesitant as that could be a sensitive area," Dawson admits, but with suggestions still coming in, he's not worried about running out of myths to investigate any time soon.

"It's a great way to get the students interested at the same time they learn the steps of scientific investigation. It teaches them how to handle bacteria, how to handle pipettes and other lab equipment," Dawson says.

Both Brad Ballieu and Judith Trevino started their scientific careers by participating in Dawson's double dipping study and are now working on Master's degrees in food science. Ballieu is working with a machine that sprays a coating onto food as a way of eliminating harmful bacteria. "I am working with non-pathogenic strains of E. coli and other bacteria; there are others working on controlling the virulent strain of E. coli."

Trevino is working with packaging sauces and cream soups in cookable pouches. Her lab is trying to increase the palatability of pouched foods by decreasing cooking time, while insuring safety. She did an internship at Campbell Soup and would like to return there when she graduates. Both want to work before going on to PhDs. And both give Dawson high marks as teacher and advisor. "He's really well-organized, which I like," Trevino says. "He's also goal oriented which is important when there are so many ideas out there."

Dawson's latest goal, encouraged by contact with literary agents, is to write a book about creating undergraduate investigative teams who search for the scientific truth behind myths such as the five second rule and George Costanza's misadventures in double dipping.

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