When I used to travel three, four, five days a week, I always wanted to eat meat when I was home. Because I felt deprived of it when I wasn’t home. (Except in New York City- and less than ten locations in the rest of the US, it was hard to find kosher meals.)

But, once I stopped traveling so much, I stopped feeling deprived. Nowadays, I have a meat meal maybe once a week. But, I do eat salads with- or for- dinner at least six times a week. But, I make them from scratch.

Back when I was married, my spouse always bought bagged salads, because she wanted to serve dinner in a hurry.  And, I always hated the use of the bagged stuff. Both because they were expensive- and because they lacked the tastiness of freshly cut vegetables.

Well, now, there’s a new reason to avoid them. It seems that the bagged salads are breeding grounds for Salmonella microbes. (Salmonella has become the source of most food-borne illnesses.) Worse yet, the juices from the leaves that get damaged in shipment and storage enhance the ability of the microbes to attach to the plastic bag.

Lettuce and spinach leaves have a high water content.  Moreover, they are extremely perishable and subject to rapid spoilage (probably because of that high water content). And, while the salad greens are normally washed before they are bagged, there still is some soil present within the leaf mass.  Plus, the wash water could be contaminated, and when coupled with potential human contact that can allow the bags to be colonized before they are sealed, things are prime for microbial colonization.  (There have been slews of reported cases of contaminated salad greens sold in grocery stores, as well as problems with bagged bean sprouts.)

You should know that there are NO FDA required standards for bagged salad items.  While some foreign countries have them (on the order of 100 CFU- colony forming units- per gram), this new data shows they are just as useless.  (There are VOLUNTARY guidelines- which, on the surface [pun intended] are adequate.  But, they are not definitive and they are voluntary.)

Dr. Primrose Freestone, along with Drs. G. Koukkidis, R. Haigh, and Natalie Allcock of the University of Leicester (UK) published the results of their research “Salad leaf juices enhance Salmonella growth, fresh produce colonisation and virulence” in Applied and Environmental Microbiology.  They found that the population of Salmonella (a virulent microbial contaminant) after five days of refrigerated storage time (the normal time and temperature at which the bagged contents find themselves on refrigerator shelves) increased from 100 to more than 100,000. Worse yet, microbial biofilms formed on the surfaces of the leafy greens.   (It is very hard to wash biofilms off a substance.)

Interestingly, the salad juices did not enhance the growth of normal microbial flora- only the Salmonella population flourished. And, not only did the numbers of microbes increase, the virulence of the Salmonella was enhanced.

As you can see from the two graphs below (taken from the article), the bag juices when mixed with sterile water (5, 10, or 20% bag juices to sterile water), all enhanced the microbial growth of the Salmonella.

So, while this does not mean that all bagged salads are a problem, it’s clear that if they are contaminated- contamination gets further enhanced within and by the salad bag and its contents. This microbial enhancement is due to the iron (found in the transferrin) within the salad components which promotes siderophore (iron chelating compounds) production by the microbes.

Caveat emptor.

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