Pre-washed spinach can still harbour bacteria, study finds

Pre-washed spinach can still harbour bacteria, study finds

The next time you’re having pre-packaged, pre-washed spinach, you might want to give your produce another good rinsing.

A new study from the University of California, Riverside revealed the rinsing process involved in cleaning pre-washed spinach may not be as effective at removing bacteria as you’d think. The two-year study showed that even after the disinfecting process, spinach contaminated with bacteria still held up to 90% of the germs.

“In the industry, they add a low level of chlorine (to the rinsing water). And its job is not to disinfect the leaves of the spinach, its job is to keep the rinse water clean so it can be reused,” said Sharon Walker, a researcher on the study and a professor of chemical and environmental engineering at the University of California, Riverside, in an interview with the Star.

“What we wanted to see was: What’s the presence now of organisms still on the leaf and are they alive? And they are there. They persist and they survive.”

Walker’s experiment was simple: her team purchased random samples of spinach labelled “pre-washed” at American grocery stores, and added E-coli to them afterwards. Running them through the rinsing process via low bleach solution, they confirmed around 90% of the bacteria lingered. On average, about 15% of the leaf saw a small percentage of the disinfectant.

Doug Sider, medical director of communicable disease prevention and control for Public Health Ontario, wasn’t surprised at the study’s results. Pre-washed isn’t synonymous with bacteria-free.

“(Prewashing) doesn’t necessarily mean pathogen-reduction to a point where we judge there is little of no risk of transmission,” he said.

Regardless if it’s pre-washed or not, the decision to purchase fresh produce is ultimately a case of buyer beware, he said.

The study wasn’t intended to stop people from buying spinach, as it’s a healthy mainstay in salads and diets in general. Walker’s study intended to make recommendations on cleaning procedures to reduce the presence of bacteria in food. She added she doesn’t believe spinach producers intentionally mislead the public with the ‘pre-wash’ label – they do intend to remove dirt and silt – but it just doesn’t mean ‘disinfected.’

If you do decide to go with the fresh produce route, here’re six tips that’ll help you get rid of those sneaky germs:

  1.  Surprise: wash produce – even if it says pre-washed – under water, using your fingers to rub the ridges of produce such as leafy greens. You might rub off a bit of extra bacteria.
  1.  Buy local. You can be more confident that proper food handling procedures were followed.
  1.  Cook or peel fresh produce. This tip is more important if you’re older, or have a weaker immune system.
  1.  Wash your hands thoroughly with soap and water before handling produce (at least 20 seconds). You don’t want to be adding even more germs than there already are!
  1.  If you’re rinsing leafy greens, toss the outer leaves. Rinse until you see zero traces of dirt, trust the eye test.

Don’t soak leafy greens in a sink-full of water – bacteria in the sink may cling onto your produce.

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