January – The Goods on Greens: Are Prepared Salads Safe?

Written by Communications, January 14, 2020

Who doesn’t love the convenience of purchasing prepared salads or prewashed greens – I know I do. But recent outbreaks of human illness, including hospitalizations and deaths are raising concerns that perhaps these pre-packaged and pre-washed salad greens pose too much of a health risk, and are best avoided. Are these products safe to eat? The excessive use of single use plastics is nowhere as visible as in the refrigerated produce section – could there be both environmental and health reasons to shun these products? Are there any steps we can take at home to reduce the associated risk?

Food handling basics suggest that a good place to start is at the kitchen sink: Current recommendations are to head directly to the sink from the grocery store or market, and take your fruits and vegetables with you. But will washing the newly purchased fruits and vegetables thoroughly under fresh, cool, running water really protect you when the food is lettuce or leafy greens? A 2017 study showed that high flows of tap water, at 8 litres/min, can mechanically remove much of the bacteria but was not able to eradicate the nasty hangers-on like E. Coli. Adding sanitizers or vinegar or lemon juice doesn’t appear to help either. And a study published in 2016 found that adding bleach to the wash, at the levels required to kill the bacteria, creates risks of its own. The bottom line is that home washing of salad greens is not an effective strategy.

Bacterial contamination is a relatively rare event but it does happen, and when present, these bacteria may not be easily washed away, even if the consumer chooses to wash before use. In December 2019 alone, there were recalls of pre-cut salads, coleslaw and romaine lettuce, all linked to bacterial contamination with resulting outbreaks in humans. Warnings from consumer organizations following an E. Coli outbreak early in 2019 recommended that consumers cook their vegetables as a tried and true method to reduce the risk. High temperatures destroy microbes that are present in food, making it safer to eat. So, it may be an option to cook the spinach but does that mean we should stop eating salads? What is a salad-lover to do??

Unfortunately, lettuce is very susceptible to contamination from bacteria present in the soil, in improperly composted manure or in the water used for irrigation. Because lettuce is so close to the ground, irrigation or even a heavy rain can cause the leaves to become splashed. Tumbling and washing the greens is not enough to eradicate the contaminants. Added to that is the opportunity for bacteria to be introduced post-harvest, somewhere along the long journey from a faraway field to fork.

Separating livestock from vegetable production, and ensuring the safety of irrigation water could make the leafy greens we have come to love, safer. Greens produced in greenhouses are a safer choice for now. In season, growing your own salad greens or purchasing from local producers who adhere to good growing practices are also good choices. Some speculate that the growing popularity of kale, a much hardier leaf grown further away from the ground, may be attributed to past outbreaks of E. Coli linked to lettuce and spinach. Kale, which can tolerate a vigorous wash in the sink, may indeed be a better choice for those craving something fresh in the winter. And let us not forget that before California and Arizona had figured out a way to ship lettuce, it was cabbage that provided the crunch in our winter salads.

With prepackaged greens, as with other products like raw milk cheese or processed meats that can harbour harmful bacteria like Listeria, it may be best for household members and guests like the very young, or the elderly, pregnant women and people who are immunocompromised, to avoid them. For good advice on food choices from a food safety perspective, visit www.peterboroughpublichealth.ca.

And while we are talking about precaution, remember that anyone preparing food can unintentionally spread whatever they are incubating or shedding. Hand washing before handling food is always a good idea. Keep ill volunteers out of the kitchen – they are not the ones you want handling the bread or preparing the salad. Kale salad, that is.