四级快速阅读

（一）

Is itreally OK to eat food that’s fallen on the floor?

A.When you drop a piece of food on the floor, is it really OK to eat you pick itup within five seconds? An urban food myth contends that if food spends just afew seconds on the floor, dirt and germs won’t have much of a chance tocontaminate it. Research in my lab has focused on how food becomescontaminated, and we’ve done some work on this particular piece of wisdom.

B.While the “five-second rule” might not seem like the most pressing issue forfood scientists to get to the bottom of, it’s still worth investigating foodmyths like this one because they shape our beliefs about when food is safe toeat.

C.So is five seconds on the floor the criticalthreshold（门槛）that separates a pieceof eatable food from a case of food poisoning? It’s a bit more complicated thanthat. It depends on just how many bacteria can make it from floor to food in afew seconds and just how dirty the floor is.

D.Wondering if food is still OK to eat after it’s dropped on the floor is apretty 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,TheFrench Chef, insist they saw Child drop lamb on the floor and pick it up,with the advice that if they were along in the kitchen, their guests wouldnever know.

E.In fact it was a potato pancake, and it fell on the stovetop, not on the floor.Child put it back in the pain, saying. “But you can always pick it up and ifyou’re alone in the kitchen, who’s going to see it?” But the misrememberedstory persists. It’s harder to pin down the origins of the oft-quotedfive-second rule, but a 2003 study reported that 70% of women and 56% of mensurveyed were familiar with the five-second rule and that women were morelikely than men to eat food that had dropped on the floor.

F.So what does science tell us about what a few moments on the floor means forthe safety of your food? The earliest research report on the five-second ruleis attributed to Jillian Clarke, a high school student participating in aresearch apprenticeship at the University of Illinois. Clarke and hercolleagues inoculated floor tiles with bacteria then placed food on the tilesfor varying times. They reported bacteria were transferred from the tile togummy bears and cookies within five seconds, but didn’t report the specificamount of bacteria that made it from the tile to the food.

G.But how much bacteria actually transfer in five seconds? In 2007, my lab atClemson University published a study–the only peer-reviewed journal paper on this topic–in the Journal of AppliedMicrobiology. We wanted to know if the length of time food is in contact with acontaminated surface affected the rate of transfer of bacteria to the food. Tofind out, we inoculated squares of tile, carpet or wood with Salmonella. Fiveminutes 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 thefood. We repeated this exact protocol after the bacteria had been on thesurface for two, four, eight and 24 hours.

H.We found that the number of bacteria transferred to either kind of food didn’tdepend much on how long the food was in contact with the contaminatedsurface—whether for a few seconds or for a whole minute. The overall amount ofbacteria on the surface mattered more, and this decreased over time after theinitial inoculation. It looks like what’s at issue is less how long your food stayson the floor and much more how contaminated with bacteria that patch of floorhappens to be.

I.We also found that the kind of surface made a difference as well. Carpets, forinstance, seem to be slightly better places to drop your food than wood ortile. When carpet was inoculated with Salmonella, less than 1% of the bacteriawere transferred. But when the food was in contact with tile or wood, 48%-70%of bacteria transferred.

J.Last year, a study from Aston University in the UK used nearly identicalparameters（参数）to our study andfound similar results testing contact times of three and 30 seconds on similarsurfaces. They also reported that 87% of people asked either would eat or haveeaten food dropped on the floor.

K.Should you eat food fallen on the floor then? From a food safety standpoint,you have millions or more bacteria on a surface, 0.1% is still enough to makeyou sick. Also, certain types of bacteria are extremely harmful and it takesonly a small number to make you sick. For example, 10 bacteria or less of anespecially deadly strain of bacteria can cause severe illness and death inpeople with compromised immune systems. But the chance of these bacteria beingon most surfaces is very low.

L.And it’s not just dropping food on the floor that can lead to bacterialcontamination. Bacteria are carried by various “media,” which can include rawfood, moist surfaces where bacteria has been left, our hands or skin and fromcoughing or sneezing. Hands, foods and utensils can carry individual bacterialcells, colonies of cells or cells living in communities contained within aprotective film that provide protection. These microscopic layers of depositscontaining bacteria are known as biofilms and they are found on most surfacesand objects. Biofilm communities can harbor bacteria longer and are verydifficult to clean. Bacteria in these communities also have an enhancedresistance to sanitizers and antibiotics compared to bacteria living on theirown.

M.So the next time you consider eating dropped food, the odds are in your favorthat you can eat that morsel and not get sick. But in the rare chance thatthere is a microorganism that can make you sick on the exact spot where thefood dropped, you can be fairly sure the bug is on the food you are about toput in your mouth.

N.Research or common sense tells us that the best thing to do is to keep yourhands and other surfaces clean.

36.A research project found bacteria made their way to the food on the floor infive seconds.

37.Whether food is contaminated depends much on the number of bacteria that getonto it.

38.Food contamination may result from various factors other than food dropping onthe floor.

39.Males are less likely than females to eat food that may have been contaminated.

40.The author’s research center around how food gets contaminated.

41.Keeping everything clean is the best way to stay healthy.

42.Chances are you will not fall sick because of eating food picked up from thefloor.

43.For a long time people have had the experience of deciding whether or not toeat food picked up from the floor.

44.Some strains of bacteria are so harmful that a tiny few can have deadlyconsequences.

45.Researcher found how many bacteria get onto the food did not have much to dowith how long the food stayed on a contaminated floor.

36-45 FCLEA NMDKH