Explainer: is it really OK to eat food that’s fallen on the floor?
When you drop a piece of food on the floor, is it really OK to eat if you pick up within five seconds? This urban food myth contends that if food spends just a few seconds on the floor, dirt and germs won’t have much of a chance to contaminate it. Research in my lab has focused on how food and food contact surfaces become contaminated, and we’ve done some work on this particular piece of wisdom.
While the “five-second rule” might not seem like the most pressing issue for food scientists to get to the bottom of, it’s still worth investigating food myths like this one because they shape our beliefs about when food is safe to eat.
So is five seconds on the floor the critical threshold that separates an edible morsel from a case of food poisoning? It’s a bit a more complicated than that. It depends on just how much bacteria can make it from floor to food in a few seconds and just how dirty the floor is.
Where did the five-second rule come from?
Wondering if food is still OK to eat after it’s been dropped on the floor (or anywhere else) is a pretty common experience. And it’s probably not a new one either.
A well-known, but inaccurate, story about Julia Child may have contributed to this food myth. Some viewers of her cooking show, The French Chef, insist they saw Child drop lamb (or a chicken or a turkey, depending on the version of the tale) on the floor and pick it up, with the advice that if they were alone in the kitchen, their guests would never know.
In fact it was a potato pancake, and it fell on the stovetop, not on the floor. Child put it back in the pan, saying “But you can always pick it up and if you are alone in the kitchen, who is going to see?” But the misremembered story persists.
It’s harder to pin down the origins of the oft-quoted five-second rule, but a 2003 study reported that 70% of women and 56% of men surveyed were familiar with the five-second rule and that women were more likely than men to eat food that had been dropped on the floor.
So what does science tell us about what a few moments on the floor means for the safety of your food?
Five seconds is all it takes
The earliest research report on the five-second rule is attributed to Jillian Clarke, a high school student participating in a research apprenticeship at the University of Illinois. Clarke and her colleagues inoculated floor tiles with bacteria then placed food on the tiles for varying times.
They reported bacteria were transferred from the tile to gummy bears and cookies within five seconds, but didn’t report the specific amount of bacteria that made it from the tile to the food.
But how much bacteria actually transfer in five seconds?
In 2007, my lab at Clemson University published a study – the only peer-reviewed journal paper on this topic – in the Journal of Applied Microbiology. We wanted to know if the length of time food is in contact with a contaminated surface affected the rate of transfer of bacteria to the food.
To find out, we inoculated squares of tile, carpet or wood with Salmonella. Five minutes after that, we placed either bologna or bread on the surface for five, 30 or 60 seconds, and then measured the amount of bacteria transferred to the food. We repeated this exact protocol after the bacteria had been on the surface for two, four, eight and 24 hours.
We found that the amount of bacteria transferred to either kind of food didn’t depend much on how long the food was in contact with the contaminated surface – whether for a few seconds or for a whole minute. The overall amount of bacteria on the surface mattered more, and this decreased over time after the initial inoculation. It looks like what’s at issue is less how long your food languishes on the floor and much more how infested with bacteria that patch of floor happens to be.
We also found that the kind of surface made a difference as well. Carpets, for instance, seem to be slightly better places to drop your food than wood or tile. When carpet was inoculated with Salmonella, less than 1% of the bacteria were transferred. But when the food was in contact with tile or wood, 48%-70% of bacteria transferred.
Last year, a study from from Aston University in the UK used nearly identical parameters to our study and found similar results testing contact times of three and 30 seconds on similar surfaces. They also reported that 87% of people asked either would eat or have eaten food dropped on the floor.
Should you eat food that’s fallen on the floor?
From a food safety standpoint, if you have millions or more cells on a surface, 0.1% is still enough to make you sick. Also, certain types of bacteria are extremely virulent, and it takes only a small amount to make you sick. For example, 10 cells or less of an especially virulent strain of E. coli can cause severe illness and death in people with compromised immune systems. But the chance of these bacteria being on most surfaces is very low.
And it’s not just dropping food on the floor that can lead to bacterial contamination. Bacteria are carried by various “media,” which can include raw food, moist surfaces where bacteria has been left, our hands or skin and from coughing or sneezing.
Hands, foods and utensils can carry individual bacterial cells, colonies of cells or cells living in communities contained within a protective film that provide protection. These microscopic layers of deposits containing bacteria are known as biofilms and they are found on most surfaces and objects.
Biofilm communities can harbor bacteria longer and are very difficult to clean. Bacteria in these communities also have an enhanced resistance to sanitizers and antibiotics compared to bacteria living on their own.
So the next time you consider eating dropped food, the odds are in your favor that you can eat that morsel and not get sick. But in the rare chance that there is a microorganism that can make you sick on the exact spot where the food dropped, you can be fairly sure the bug is on the food you are about to put in your mouth.
Research (and common sense) tell us that the best thing to do is to keep your hands, utensils and other surfaces clean.
What’s your Easter bunny made of? Could it have palm oil in it?
It may come as no surprise that fats and oils are part of any piece of chocolate we eat. But the push to cut trans fats from food for health reasons has created demand for palm oil, an ingredient with significant environmental impacts.
The rapid expansion of palm oil production for food and biofuels in the past 25 years in Indonesia and Malaysia has been blamed for loss of biodiversity and land-use changes that increase carbon emissions. About 80% of palm oil production goes into food, according to a web site sponsored by the Malaysian Palm Oil Board.
Palm oil is used in many candies with chocolate, although a number of confectionery producers do not use it or have started to use certified sustainable palm oil. The El Paso Zoo is just one of the organizations that lists candy products with palm oil, including goodies for a palm oil-free Easter basket filler.
The conversation around palm oil clearly illustrates the conundrum often created by single-issue activism and why we must think holistically about the food system.
Before you bite that chocolate bunny
Fats and oils can be of animal origin, such as butter fat, tallow and lard, or of vegetable origin, such as soy bean oil, canola oil or palm oil. Natural fats are generally processed to remove gums, colors and odors. Their solid and liquid components may be separated into their component fats stearins and oleins, and oils may be hydrogenated to render them more solid.
The US standard of identity for chocolate permits only two fats: cocoa butter, the natural fat of the tree Theobroma cacao, and milk fat, which is also known as butter oil.
If any other “safe and suitable” vegetable fat, oil or stearin is added, the product may no longer be labeled “chocolate.” Instead, it legally becomes “sweet cocoa and vegetable fat coating,” “sweet chocolate and vegetable fat coating,” “milk chocolate and vegetable fat coating,” or more commonly known as chocolate-flavored confectioners’ coatings. Alternatively, the common or usual name of the vegetable-derived fat ingredient may be used in the name of the food, such as “sweet cocoa and palm oil coating.”
Most chocolate confections are not made of solid chocolate, and other vegetable fats and oils find their way into the fillings, centers or inclusions. For example, a truffle center might contain hazelnut paste, which is about 60% hazelnut oil, and a peanut butter cup obviously contains peanut oil. In these composite “candy bars” the technical properties of the fat, notably its melting point, are extremely important.
The melting point of liquid oils can be increased through hydrogenation of unsaturated fatty acids. Unfortunately, trans fatty acids may be created in this process and they have been shown to increase LDL cholesterol and decrease HDL cholesterol and, therefore, may increase the risk of coronary heart disease.
Enter palm oil
Consumers have expressed a desire for products with fewer ingredients and “cleaner,” simpler labels. As of January 2006, the Food & Drug Administration has required labels to include the trans fat content. In response, the food industry has sought means of reducing the trans fats, including the use of natural fats that have properties similar to hydrogenated oils and improvements in the hydrogenation process that avoid the formation of trans fatty acids.
Palm oil is obtained from the pulp of the fruit of one or more species of oil palm, principally Elaeis guineensis. It is a common cooking oil in tropical regions of Africa, Asia and South America. It is naturally reddish in color due to high levels of beta-carotene. It is not the same as palm kernel oil, derived from the same plant, or coconut oil obtained from the coconut palm, Cocos nucifera. Palm oil is a moderately saturated fat (about 40%) making it semi-solid at room temperature and a good technical substitute for hydrogenated oils.
Real health benefit?
There is some concern that substituting palm oil for trans fatty acid containing fats, including hydrogenated soy bean oil, may not reduce the risk of coronary heart disease. A recent meta-analysis of dietary intervention trials incorporating palm oil concluded that both favorable and unfavorable changes in risk occurred when palm oil was substituted for other dietary fats.
Yet the growing consumer demand for trans fat-free products has stimulated the rapid expansion of palm oil plantations, often at the expense of native forests. This has been particularly acute in Indonesia, where habitat destruction has threatened the orangutan.
In response, the Roundtable on Sustainable Palm Oil (RSPO), an industry-led organization, promulgated the Certified Sustainable Palm Oil standards. According to RSPO’s website, only 18% of global palm oil is certified.
It seems straightforward to demand that food manufacturers simply remove trans fats from the diet, but in doing so we need to consider what they will be replaced by. Similarly, we can avoid eating palm oil, but what will we eat instead and what effect will that have on our health and the health of our environment?
Corks seal a wine’s fate: aging under natural vs synthetic closures
Most foods are best as fresh as possible. I remember picking peaches at my grandfather’s ranch in Northern California and eating them on the spot. What a taste! But the exceptions to this rule are the many wines that actually need some aging to taste their best. Winemakers know this, and work to control the aging process including decisions they make about how to bottle up their product.
Aging and oxygen
One aspect of aging has to do with the reaction of fruit acids with the alcohol. This process reduces sourness in the wine, but it’s really only important for very tart wines, the ones coming from cold climates.
The complex oxidation process is the second aspect of aging. When oxygen interacts with a wine, it produces many changes – ultimately yielding an oxidized wine that has a nutty aroma. This is a desired taste for sherry styles, but quickly compromises the aromas in fresh white wines.
However the oxidation process provides benefits along the way to that unwanted endpoint. Many wines develop undesirable aromas under anaerobic – no oxygen – conditions; a small amount of oxygen will eliminate those trace thiol compounds responsible for the aroma of rotten eggs or burnt rubbber. Oxidation products also react with the red anthocyanin molecules from the grapes to create stable pigments in red wine.
The way a bottle is sealed will directly affect how much oxygen passes into the wine each year. That will directly affect the aging trajectory and determine when that wine will be at its “best.”
Stick a cork in it?
Glass is a hermetic material, meaning zero oxygen can pass through it. But all wine bottle closures admit at least a smidgen of oxygen. The actual amount is the key to a closure’s performance. A typical cork will let in about one milligram of oxygen per year. This sounds like a tiny bit, but after two or three years, the cumulative amount can be enough to break down the sulfites that winemakers add to protect the wine from oxidation.
There are three major closure options available: natural cork and technical cork, its low budget brother made of cork particles, the screw cap and synthetic corks. Natural cork closures appeared about 250 years ago, displacing the oiled rags and wooden plugs that had previously been used to seal bottles. It created the possibility of aging wine. Until 20 years ago natural corks were pretty much the only option for quality wine. It’s produced from the bark of the tree, and harvested every seven years throughout the life of a cork oak tree, Quercus suber. The cork cylinder is cut from the outside to the inside of the bark.
A small fraction of corks, 1-2% today, end up tainting the wine with a moldy smelling substance, trichloroanisole. This TCA is created via a series of chemical reactions in the bottle: chlorine from the environment reacts with the natural lignin molecules in the woody cork to make trichlorophenol, which is in turn methylated by mold. TCA has one of the most potent aromas in the world – some people can smell as little as 2 parts per trillion in wine. So, in every eight cases of wine, one or two bottles will smell like wet cardboard or simply not taste their best. This is why restaurants let you taste the wine before pouring – to let you judge if the wine is tainted. A 1% failure rate seems high in today’s world.
Synthetic corks are made from polyethylene, the same stuff as milk bottles and plastic pipes. After years of research and development, these corks now perform nearly the same as the natural version with three exceptions: they have no taint, they let in a bit more oxygen and they are very consistent in oxygen transmission.
Their consistency is a major selling point to winemakers because the wine will have a predictable taste at various points in time. In fact, winemakers can tweak the oxidation rate of their wine by choosing from a range of synthetic corks with different rates of known oxygen transmission.
Screwcaps are actually two parts: the metal cap and the liner inside the top of the cap that seals to the lip of the bottle. The liner is the critical part that controls the amount of oxygen getting into the wine. Back when screwcaps were only used on jug wine, there were just two types of liners available. But today multiple companies are jumping in to offer their take on what rate of oxygen transmission is best, as well as to replace the tin used in one of the traditional liners. The standard liners admit either a bit more or a bit less oxygen than good natural corks. Screwcaps, being manufactured, are also very consistent.
Is there an optimum wine closure?
Performance of the manufactured closures, made with 21st century technology, is excellent. Generally they approximate our expectations, based on over two centuries of experience aging with natural cork closures.
For the regular wine you might purchase for dinner this weekend or to keep for a year or two, any of these closures are perfectly good, while the manufactured closures avoid taint. In fact, your choice is more a matter of preference for opening the bottle. Do you want the convenience of twisting off the cap, or do you want the ceremony of removing the cork?
For long aging however, the only closure with an adequately long track record is natural cork. So to be safe, that is the closure to choose. Once we have solid long-term evaluations of synthetics and screw caps, it will be possible to judge their suitability for extended aging, such as more than ten years.
Over centuries, winemakers have consistently taken advantage of new technology to improve their product, from oak barrels to bottles to modern crushing and pressing equipment and micro-oxygenation. While manufactured closures have some key advantages, it is proving difficult to displace natural cork due to its centuries-old tradition, albeit with a few problems, and its connection to the natural environment.
This article is part of The Conversation’s holiday series on wine. Click here to read more articles in the series.
While most Americans are roasting turkeys and emptying cranberry sauce out of cans, the station crew will be cutting open bags of freeze-dried, irradiated and thermostabilized foods.
Their menu will include traditional holiday fare with a space-food flair — irradiated smoked turkey, thermostabilized candied yams and freeze-dried green beans and mushrooms. The meal also will feature NASA’s own freeze-dried cornbread dressing — just add water. Dessert features thermostabilized cherry-blueberry cobbler.