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Bagging the Greens: Do You Know What’s in that Bag of Salad?

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Bagging the Greens: Do You Know What’s in that Bag of Salad?

Salad Bags and its Harmful Contaminants

Bagged Spinach. Photo Courtesy of Cooking Light.Bagged salad sometimes seems like more of a threat than raw meat these days, with one produce outbreak after another grabbing the headlines. In fact, the Centers for Disease Control and Prevention say that the overall incidence of foodborne illness is on the decline, but the outbreaks that happen are now more likely to be caused by contaminated produce than meat. How did we get here? Raw meat surely contains more harmful pathogens, but the difference is that the consumer has more control over the meat hazard with preparation. Meat is easily heated to the point where most worrisome microbes die. Salad can be washed and spun, but hosts surprisingly tenacious life that would be difficult to control by any means other than temperature.

The “good” news is that growing numbers of outbreaks can probably be attributed to ever-expanding cut salad consumption (and produce consumption in general) rather than worse sanitation, as consumers become both more health-conscious and convenience-minded. The leaf lettuce craze also seems in line with the trend toward supporting the small, sustainable, and local, since farmer’s markets and other forms of direct-to-consumer grower sales like CSA’s and farm-to-restaurant arrangements grow steadily more popular, and fresh cut greens are often a star among these offerings. Many growers, small and large, also see leaf lettuce as a lucrative crop, since one planting can yield several cuttings, while head lettuce gives just one harvest per crop.

Cut lettuce really took hold in 1989, when Fresh Express came out with the first prewashed, ready-to-eat, mass-produced bagged salad mix, introducing what many saw as a revolution in convenience. The cut salad market expanded rapidly since then to become the roughly $3 billion-a-year industry it is today.

The spinach business in the Salinas Valley, however  – the “nation’s salad bowl” – still hasn’t recovered from the 2006 outbreak of E. coli 0157:H7 that killed five people and sickened over a hundred in 26 states. Last year, thirty people died after eating poorly washed, Listeria-laced cantaloupe.

In the case of the spinach, E. coli, which usually inhabits mammals’ intestines, was likely tracked into the field from a nearby cattle grazing operation. With produce outbreaks, the problem often, but of course not always, spreads easily during bagging, a centralized processing situation in which thousands of leaves from many different fields are taken to a central plant and washed together, and pathogens can travel quickly in the wash water. Then leaves that have been combined from various fields get dispersed throughout the country. What started as perhaps the contamination of just a few plants in the field can quickly ruin an entire lot of cut leaves.

Companies in the Salinas Valley are waging a war against the microbial enemy, building an arsenal of heavy duty weapons. Researchers are testing new technologies in hopes of finding the perfect wash, including one candidate known as SmartWash, or T-128, an industrial salad wash additive, which reduces the risk of bacteria spreading from leaf to leaf during washing.  Other research looks at chlorine alternatives, gaseous washes, radiation, and cold plasma.

Once fresh-consumed produce becomes contaminated, it’s extremely hard to get it clean again. The easiest thing is often to contain and prevent the growth of the invader, usually by keeping temperatures cold.

Most processors currently add a cheap anti-microbial agent like chlorine. Even then, tiny amounts of pathogens can sometimes survive the chemical onslaught.

Green Oak Lettuce, San Juan Bautista, CA. Photo Courtesy of LA Times.Researchers are not only trying to figure out how to wipe out pathogens (which is looking pretty much impossible), but are looking at the biology of leafy greens and how their anatomy makes it easier for microbes to attack. Food Safety News compared pathogens on a leaf to passengers on a cruise ship: “When a leafy green is cut or torn, some of its nutrients ooze out. And just as cruise-ship passengers line up when the buffet opens, any pathogens that might be in cut salad mix head toward the nutrients. It’s supper time.” Basically what makes greens convenient – being pre-cut and pre-washed – turns out to be what also makes them susceptible to microbial infection.

Pathogens become enmeshed in biofilms, thin microscopic layers formed on the leaf’s surface by a gooey mass of bacteria, such as E. coli or Salmonella. The tightness of this binding actually makes it difficult to penetrate with many antimicrobials. “Biofilm disrupters,” in fact, are a popular emerging research target.

The Institute for Food Safety and Health in Chicago is experimenting with high-powered ultrasounds, which are used to create millions of tiny bubbles on the leaf’s surface. When the bubbles burst, they release a large amount of energy, which dislodges the pathogens into water treated with a highly acidic citrus cleanser.

Even if the perfect treatment comes on the market, the more important question is how much will most companies be willing to pay for it?

The Food and Drug Administration (FDA) now says in its Food Code that greens should be kept at and received by customers at 41 degrees F (including wholesale customers like restaurants, food-service companies, and other institutions such as schools and hospitals). If temperatures aren’t below this point, they say, any pathogens present can keep multiplying. The FDA designated cut leafy greens as a “potentially hazardous” food. Lettuce and spinach are deemed especially vulnerable, since they grow so close to the ground, making contamination from tainted runoff or irrigation water more likely. This excludes raw agricultural produce that is not processed or cut on site, like head lettuce, or herbs such as cilantro or parsley. It is quite difficult, almost impossible, for small farmers who sell cut greens direct-to-consumer to follow the temperature guidelines, since it would be beyond the means of most of these farmers to use the cooling methods they would need, like a refrigerated truck to get produce to market.

The FDA Food Code in itself is not law, but is used by states, counties, and local jurisdictions to regulate about one million food establishments.

There is much debate about whether 41 degrees Is a good one-size-fits all critical point, especially for small-scale handlers and farmers’ markets. This number was apparently chosen because 45 degrees has been observed as the lower-end temperature at which most harmful bacteria can multiply.

Some small-scale growers that can’t afford a walk-in cooler have invested in CoolBot, a cooling system that basically turns any highly-insulated room into a refrigerator, using an air-conditioning unit and a technology that interfaces with the unit, allowing the user to access the complete cooling capability of the air conditioner (which would normally not go below about 60 degrees) in an energy-efficient manner.

The main reason for such scrutiny over the cut salad industry isn’t these little guys, though; it’s in large part the massive food distribution system that allows contamination to spread so quickly from the Salinas Valley to far-flung states. Proponents of “small ag” interests protest the regulations that would make it impractical for them to sell cut greens. “Big ag” interests respond that they shouldn’t get different rules just because they’re small. This would be like giving small restaurants different health regulations than large chains, and only regulating those who can afford to comply. Small growers argue that one-size-fits all regulation does not work well, and makes the worst-case scenario the rule. Whether small producers like it or not, though, most of the food safety guidelines are things every farmer should be paying attention to – even if some become much more of an issue when large volumes of easily contaminated, raw-consumed product with very complex supply chains are at stake.

Food Safety News points out the many variables influence contamination and how far it is allowed to spread, such as distance from farm to consumers, a farm’s growing practices, how soon consumers get the produce after harvest, and the food-handling practices of consumers themselves.

Amidst the panic, it’s important to remember that the odds of getting sick from bagged greens (1 in 5.5 million, according to Food Safety News) are still far below than the odds of getting struck by lightning (1 in 310,000). The last decade has seen a rise in so-called low-dosage organisms like E. coli, Campylobacter, and Listeria. (Low-dosage means it only takes a relatively small number of the organism to sicken the victim, for example 500 for Campylobacter, as opposed to millions for Salmonella.)

Meanwhile, advice for salad eaters is and has always been conflicted. Most sources say thoroughly wash any bagged salad mix you buy (and any produce you buy, in fact, whether or not it claims to be pre-washed). Some people feel better foregoing bagged greens altogether and eating head lettuce instead, discarding the outer layers. Other sources say you may simply be making your salad dirtier by washing it, given the inevitable pathogens hanging around most people’s hands, sinks and kitchens, especially contamination from preparing raw meat nearby.

I say washing with a thorough rinse usually seems the best course of action. Consumer Reports did a mini-test of 208 bagged salads, and found that 39 percent had excessive bacteria, including fecal contamination (“excessive” meaning 10,000 or more colony forming units per gram, or CFU/g). While this is not necessarily enough to make you sick, it is sort of gross, and evidence of a more general problem with poor sanitation and fecal contamination within the industry. And that has to be dirtier than most people’s kitchen! Other than washing, the next best thing to do is buy the newest greens you can get your hands on – at least 5-8 days before the sell by date. The longer they sit around, and yes, at high temperatures, the more opportunity bacteria has to multiply.  But it might be safer still to buy the separate salad elements and wash and chop them yourself. Or even grow them yourself.

Genevieve Slocum is a Contributor to The Free George.

The Free George is the online magazine and visitors’ guide of Upstate NY, covering things from Albany to Lake Placid, including Saratoga, the Lake George region and the Adirondacks. Check out our City Blogs section for our extended coverage areas as well.

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