How bad is double-dipping?? Paul Dawson explains @US_Conversation

Is double-dipping a food safety problem or just a nasty habit?

Paul Dawson, Clemson University

What do you do when you are left with half a chip in your hand after dipping? Admit it, you’ve wondered whether it’s OK to double dip the chip.

Maybe you’re the sort who dips their chip only once. Maybe you look around the room before loading your half-eaten chip with a bit more dip, hoping that no one will notice.

If you’ve seen that classic episode of Seinfeld, “The Implant,” where George Costanza double-dips a chip at a wake, maybe you’ve wondered if double-dipping is really like “putting your whole mouth right in the dip!

‘You doubled-dipped the chip.’

But is it, really? Can the bacteria in your mouth make it onto the chip then into the dip? Is this habit simply bad manners, or are you actively contaminating communal snacks with your particular germs?

This question intrigued our undergraduate research team at Clemson University, so we designed a series of experiments to find out just what happens when you double-dip. Testing to see if there is bacterial transfer seems straightforward, but there are more subtle questions to be answered. How does the acidity of the dip affect bacteria, and do different dips affect the outcome? Members of the no-double-dipping enforcement squad, prepare to have your worst, most repulsive suspicions confirmed.

Start with a cracker

Presumably some of your mouth’s bacteria transfer to a food when you take a bite. But the question of the day is whether that happens, and if so, how much bacteria makes it from mouth to dip. Students started by comparing bitten versus unbitten crackers, measuring how much bacteria could transfer from the cracker to a cup of water.

We found about 1,000 more bacteria per milliliter of water when crackers were bitten before dipping than solutions where unbitten crackers were dipped.

In a second experiment, students tested bitten and unbitten crackers in water solutions with pH levels typical of food dips (pH levels of 4, 5 and 6, which are all toward the more acidic end of the pH scale). They tested for bacteria right after the bitten and unbitten crackers were dipped, then measured the solutions again two hours later. More acidic solutions tended to lower the bacterial numbers over time.

The time had come to turn our attention to real food.

But what about the dip?

We compared three kinds of dip: salsa, chocolate and cheese dips, which happen to differ in pH and thickness (viscosity). Again, we tested bacterial populations in the dips after already-bitten crackers were dipped, and after dipping with unbitten crackers. We also tested the dips two hours after dipping to see how bacterial populations were growing.

We tested All Natural Tostitos Chunky Hot Salsa (pH 4), Genuine Chocolate Flavor Hershey’s Syrup (pH 5.3) and Fritos Mild Cheddar Flavor Cheese Dip (pH 6.0).

So, how dirty is your dip? We found that in the absence of double-dipping, our foods had no detectable bacteria present. Once subjected to double-dipping, the salsa took on about five times more bacteria (1,000 bacteria/ml of dip) from the bitten chip when compared to chocolate and cheese dips (150-200 bacteria/ml of dip). But two hours after double-dipping, the salsa bacterial numbers dropped to about the same levels as the chocolate and cheese.

After two hours, levels of bacteria in the salsa were similar to levels in the cheese and chocolate dips.
Paul Dawson, Author provided

We can explain these phenomena using some basic food science. Chocolate and cheese dips are both pretty thick. Salsa isn’t as thick. The lower viscosity means that more of the dip touching the bitten cracker falls back into the dipping bowl rather than sticking to the cracker. And as it drops back into the communal container, it brings with it bacteria from the mouth of the double-dipper.

Salsa is also more acidic. After two hours, the acidity of the salsa had killed some of the bacteria (most bacteria don’t like acid). So it’s a combination of viscosity and acidity that will determine how much bacteria gets into the dip from double-dipping. As a side note about party hosting: cheese dip will run out faster than salsa since more of the cheese sticks to the cracker or chip on each dip. That could reduce the chances of people double-dipping. And yes, this is something we discovered during the experiment.

Should I freak out about double-dipping?

Double-dipping can transfer bacteria from mouth to dip, but is this something you need to worry about?

Anywhere from hundreds to thousands of different bacterial types and viruses live in the human oral cavity, most of which are harmless. But some aren’t so good. Pneumonic plague, tuberculosis, influenza virus, Legionnaires’ disease and severe acute respiratory syndrome (SARS) are known to spread through saliva, with coughing and sneezing aerosolizing up to 1,000 and 3,600 bacterial cells per minute. These tiny germ-containing droplets from a cough or a sneeze can settle on surfaces such as desks and doorknobs. Germs can be spread when a person touches a contaminated surface and then touches their eyes, nose or mouth.

That’s why the Centers for Disease Control and Prevention strongly recommends covering the mouth and nose when coughing and sneezing to prevent spreading “serious respiratory illnesses like influenza, respiratory syncytial virus (RSV), whooping cough, and severe acute respiratory syndrome (SARS).” With that in mind, there may be a concern over the spread of oral bacteria from person to person thanks to double-dipping. And a person doesn’t have to be sick to pass on germs.

One of the most infamous examples of spreading disease while being asymptomatic is household cook Mary Mallon (Typhoid Mary), who spread typhoid to numerous families in 19th-century New England during food preparation. Science has left unanswered whether she was tasting the food as she went along and, in effect, double-dipping. Typhoid Mary is obviously an extreme example, but your fellow dippers might very well be carrying cold or flu germs and passing them right into the bowl you’re about to dig into.

If you detect double-dippers in the midst of a festive gathering, you might want to steer clear of their favored snack. And if you yourself are sick, do the rest of us a favor and don’t double-dip.

The Conversation

Paul Dawson, Professor of Food Science, Clemson University

This article was originally published on The Conversation. Read the original article.

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Superbugs!! The Empire Strike Bacteria – @Okaytobesmart video! #science

Superbugs: The Empire Strikes Bacteria

Are we entering the post-antibiotic era? Antibiotic-resistant bacteria are on the rise, with millions of infections reported every year and thousands of deaths. How does antibiotic resistance work? How did we get here? And what can we do in the future to make sure that papercuts don’t spell a death sentence?

New interactive map shows the germs at your local NYC subway stop! Fun… and scary!! #science

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Check out this awesome interactive map of the bacteria in New York City’s subway system (from the Wall Street Journal)!! The map is one of the results of a huge project looking at bacteria and other germs and microbiology in the City’s transit system! Above I took a screenshot of the map for the subway station next to Columbia Presbyterian Hospital at 168th St, including 108 bacteria that can cause all sorts of problems – including antibiotic resistant bacteria! This is a super fun tool…. unless you’re a germaphobe, in which case it is horrifying  :/

Every day, New York City’s 5.5 million commuters seed the city subways with bacteria from the food they eat, the pets or plants they keep, and their shoes, sneezes and unwashed hands.

For the first time, researchers at Weill Cornell Medical College sampled DNA in New York City’s 466 open subway stations. They found genetic material from 15,152 different species, most of them harmless or unidentified. Almost half the DNA belonged to bacteria. No two subway stations were exactly the same, and the research continues.

So far, the scientists have identified 67 bacteria species associated with disease and infections. Here are details on a few of the bacteria found.

Rodent Problems? Awesome study of New York City rats finds disease causing bacteria and viruses! #science

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A study published in mBio (shout out for OpenAccess!) found that rats in New York City are very, very, very ‘dirty.’ The authors (Shout out to Columbia!) analyzed the pathogens carried by 133 rats using high-throughput genetic sequencing, and discovered that NYC rats carry many bacteria and viruses that can cause human disease! Press release here.

We found that these rats are infected with bacterial pathogens known to cause acute or mild gastroenteritis in people, including atypical enteropathogenic Escherichia coliClostridium difficile, and Salmonella enterica, as well as infectious agents that have been associated with undifferentiated febrile illnesses, including Bartonella spp., Streptobacillus moniliformisLeptospira interrogans, and Seoul hantavirus. We also identified a wide range of known and novel viruses from groups that contain important human pathogens, including sapoviruses, cardioviruses, kobuviruses, parechoviruses, rotaviruses, and hepaciviruses.

That’s not good. Now, I’ll only be thinking about all of these pathogens when I’m waiting on the subway platform and look down to see the most common NYC wildlife under the tracks. Guess we should all be paying a little more attention to the diseases that these rats are carrying around all over our city.

Our findings indicate that urban rats are reservoirs for a vast diversity of microbes that may affect human health and indicate a need for increased surveillance and awareness of the disease risks associated with urban rodent infestation.

For all of the curious minds like me, you have to ask yourself… where did they get these rats? and how did they catch them? First off, the rats were humanely euthanized after being trapped. Below are the methods from the paper describing the rat collection.

The preliminary nature of this study and the significant complexities involved in trapping rats indoors in NYC necessitated an approach of convenience sampling. An effort was made to target neighborhoods likely to be impacted by the presence of rats, specifically those with high rodent and human density or a high probability of rodent-human interaction. Five sites were selected in midtown and lower Manhattan, comprised of three high-density housing complexes, one very large indoor mixed-use public space (transportation, food service, retail, and commercial), and one small urban park in a densely populated area. The residential sites are on blocks of average density for Manhattan and below-average median income (64). The mixed-use public space is in a neighborhood notable for an exceptionally high daytime population size and density, and the park was chosen based both on its location (adjacent to the residential sites) and high block density.

For extra fun, check out this video about the study from Slate!

Tired of soap? Showering? Just spritz yourself with some bacteria

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Randomly saw this article in the NYTimes about some interesting shower science. AOBiome is trying to create a bacterial ‘shower’ that will improve the microbiome of the skin while avoiding harsh soaps and shampoos that strip us of any healthy ‘bacteria’. The microbiome (the bacterial makeup within our guts and on our skin) is a pretty hot topic right now. The principle idea is that if you colonize bacteria that breakdown ammonia on your skin, it will naturally cleanse you. Obviously to do this effectively, you have to do 2 things, first get the bacteria on your skin (spritz of AO+ from AOBiome, https://www.aobiome.com), and second, don’t use soaps that will remove it from your skin. Read the NYTimes article for a fun personal account of how this works. I find this all very interesting, but definitely want to see some hardcore data before I would give it a try. I also really like that the initial identification of potentially beneficial bacteria was based on horses rolling around in the dirt.  Looking forward to seeing the results of a good study on this. Go Bacteria!!!