Rewashing those pre-washed greens isn’t doing anything

Posted on December 27, 2018 by Ben Chapman

If I’m eating pre-washed lettuce I just open the bag and throw it on the plate. Because there’s not much I can do, safety-wise, to it once it’s in my home. If there’s pathogenic E. coli, Listeria or Salmonella there (or others) I’m stuck with it.

Cindy Tran of the Daily Mail writes that Sydney, Australia nutritionist Susie Burrell recently talked about food safety risks on a local morning show including a recommendation to rewash prewashed leafy greens.

She said people should always wash their store-bought salads, even if the packaging says ‘pre-washed’.

‘You must wash those ones out of the bags. It does say pre-washed but I would always wash it again because it has sat there for a long period, you don’t know what the turnover time is.’

I’m following recommendations from a bunch of my food safety friends who reviewed the literature on cut, bagged, washed, ready-to-eat leafy greens from a few years ago. In the abstract, they write:

The panel concluded that leafy green salad in sealed bags labeled “washed” or “ready-to-eat” that are produced in a facility inspected by a regulatory authority and operated under cGMPs, does not need additional washing at the time of use unless specifically directed on the label.

Leafy green food safety risks need to be addressed before they get to me, all I can do by washing it again is increase the chance I cross-contaminate the salad precursor in my home. My purchasing choice is based in trust that growers, packers and processors know what they are doing, and do it. But at best, they can only remove 90-99% of what is there with a wash.

And I can’t do any better.

Washing raw poultry increases cross-contamination

Posted on September 22, 2017 by Robert Mancini

Campylobacter jejuni is an important human pathogen commonly associated with raw poultry. The risk of cross-contamination in the kitchen is escalated with washing raw poultry in the sink- an unnecessary measure for food safety. Cook the bird to an internal temperature of 74°C (165°F), no need for washing.

Holly Van Hare of The Daily Meal reports:

You’re spraying your sink with salmonella
Washing your fruit? Absolutely. Washing your lettuce? Necessity. But running warm water over a slimy slab of raw chicken is just about the worst thing you can do with your kitchen sink.
In fact, it’s such a bad idea that the National Health Service (NHS) in Britain issued a public warning against the “sanitary” practice — claiming that “it can increase your risk of food poisoning from campylobacter bacteria.”
Chicken is one of the most commonly infected raw foods when it comes to foodborne bacteria such as salmonella. These bacteria lurk both on the surface and insides of the raw meat, growing indefinitely until you cook them dead. “Only a few campylobacter cells are needed to cause food poisoning,” the NHS says.
Washing the chicken involves running tap water over that infested piece of meat. The water becomes contaminated as soon as it hits the surface of your poultry, and proceeds to splash in every direction both inside and around your kitchen sink. “Water droplets can travel more than 50 centimeters in every direction,” the NHS warns, a distance that equates to over one and a half feet.
After that bacteria spreads, it’s hard to get rid of. The only real way to effectively kill the bacteria you’ve now sprinkled around your home is to disinfect everything — an onerous task you’re likely saving until after you’re done cooking. That means your risk of exposure is prolonged and the bacteria could even come into contact with your other food.
If you’re preparing chicken, skip the washing step. The oven kills everything, anyway — and once a chicken is properly cooked, it’s 100 percent free of disease-causing bacteria. If you’re bored with bland old chicken and looking to spice things up, here are 101 of our best recipes.

It’s all over now: Another UK E. coli O157 mystery with hundreds sick

Posted on August 17, 2016 by Douglas Powell

There’s a reason the Britain’s contribution to global cuisine is mushy peas and mad cow disease.

I get the UK is a small island, sinking in all kinds of animal shit, but tell us what you are doing for on-farm food safety?

And don’t answer with some bogus certification scheme.

Beginning in December 2010, a subtype of E. coli O157, began sickening Brits and resulted in over 250 sick with 80 hospitalizations, four with hemolytic uremic syndrome, and one death.

Dr. Andrew Wadge, chief scientist at the Food Standards Agency was reported as saying “This outbreak is a timely reminder that it is essential to wash all fruits and vegetables, including salad, before you eat them, unless they are labeled ‘ready to eat’, to ensure that they are clean. It is also important to wash hands thoroughly as well as clean chopping boards, knives and other utensils after preparing vegetables to prevent cross contamination.”

This advice is of limited use. Maybe a 1-log reduction use.

But it blames consumers.

The outbreak was linked to the handling of raw leeks and potatoes, and a public warning was given – reportedly months after a guidance had been issued the food industry on reducing the risk of E. coli cross-contamination.

In Nov. 2015, the BBC reported the number of people infected with E. coli across England rose by more than 1,000 over the previous year.

Public Health England figures show there were 39,604 from September 2014 to September 2015, compared with 38,291 for the same period the year before.

Another mysterious affliction.

Now, once again, the PhD health types are baffled by an outbreak of E. coli O157 in the UK that has sickened at least 161.

Those same health-thingies do say the likely cause of the outbreak was imported mixed salad leaves.

The last recorded case of the bug was on July 5 and now PHE has declared the outbreak over.

People are being urged to remove any loose soil before storing vegetables and thoroughly wash all vegetables and salads that will be eaten raw unless they have been pre-prepared and are labelled ‘ready to eat’.

Because the Brits have a long history of blaming consumers for something that should be controlled on the farm.

Washing salad is no magic bullet; safe sources matter

Posted on July 19, 2016 by Ben Chapman

I’ve become increasingly fond of the convenience of pre-washed, bagged, fresh salad mix. A staple of my weekly meals is 4oz of steak, a crumble of blue cheese, grilled mushrooms, sliced pear, a few walnuts all over a bed of 50/50 mix of pre-washed baby spinach and and mesclun mix.

I just open the bag and throw the salad on the plate.

Because there’s not much I can do, safety-wise, to it once it’s in my home. If there’s pathogenic E. coli, Listeria or Salmonella there (or others) I’m stuck with it. I’m following recommendations from a bunch of my food safety friends who reviewed the literature on cut, bagged, washed, ready-to-eat leafy greens from a few years ago.

In the abstract, they write:

Some folks, according to BBC News, disagree. They say things like:

‘washing foods is not 100% fail-safe, but it gives people the best chance against infection.’

and

‘we always wash everything, especially if we’re going to eat it raw. We don’t use much bagged salad or spinach, but if we did, we would definitely wash it.’

I’ll stick with the science.

But what exactly are the best ways to wash your greens? The BBC asked two food industry professionals for the best practice in food safety and hygiene when it comes to salad and vegetables.

Camilla Schneideman worked in the food industry for 18 years having run her own restaurants abroad and in the UK, and is currently the managing director of the Leiths Cookery School in London.

Rosalind Rathouse is a professional cook with more than 50 years of experience, who runs the Cookery School in central London.

Ms Rathouse advises storing all salad and vegetables in a cold environment, because it slows down the rate at which bacteria multiply.

What about ready-to-eat pre-packed salads?

Pre-packed salads are often washed in a low-chlorine solution to kill off the bugs, according Ms Schneideman, so eating straight from the bag is unlikely to harm you.

“It comes down to personal choice whether you want to give it an extra wash,” she said.

Soaking stuff all together also seems like a recipe for cross contamination. If I am washing something I’m going to rinse it down the drain.

‘Free fruit for kids’ PR stunt backfires for Australian grocery chain

Posted on January 11, 2016 by Douglas Powell

Woolworth’s in Australia is giving away free fruit to kids.

This has sparked some sort of hygiene uproar.

But it’s wrong.

As I told Elizabeth Weise of USA Today back in 2012, all washing of produce might do is “remove the snot that some 3-year-old blew onto the food at the grocery store.” Washing “lowers the pathogen count a little, but not to safe levels if it’s contaminated.”

The key to safe produce is food safety protocols – and verification – beginning on the farm through to retail, like Woolies.

But Woolies won’t talk about that, or market it, so I stay away.

Woolies’ “free fruit for kids” initiative has backfired, with shoppers complaining the basket of apples and bananas is unhygienic.

The supermarket giant announced the program in November, claiming it would “help children eat their recommended two serves of fruit a day and is part of Woolworths commitment to inspire a healthier Australia.”

But customers have raised concerns that kids often have dirty hands and encouraging them to touch and eat fruit in-store could spread worms or other infectious disease.

“It’s unhygienic,” Kathy, a customer in Surry Hills, Sydney, told news.com.au. “Parents should be responsible for feeding their kids, having foods there unmonitored is a bad idea.”

On a Reddit thread on the free fruit scheme, Svedka posted, “Seriously though, that’s how you get worms”, while another user added, “Cue fruit peels left in strange places around the store, and kids with pear-juice hands touching things.”

The plan was derided as “cheap advertising” and an effort by beleaguered Woolies to “attract families back to their stores

But other shoppers applauded the plan, with Alex McCowan telling news.com.au: “I don’t think it’s unhygienic. They have fruit sitting there anyway for people to buy and eat. It’s a good idea to get kids to eat more fruit. Food’s expensive, so it helps families.”

Leafs are bumpy: Change in disinfecting spinach, salad greens could reduce illness

Posted on August 19, 2015 by Douglas Powell

Cross contamination in commercial processing facilities that prepare spinach and other leafy greens for the market can make people sick. But researchers are reporting a new, easy-to-implement method that could eliminate or reduce such incidences.

The scientists will present their work at the 250th National Meeting & Exposition of the American Chemical Society (ACS).

Spinach or other leafy salad greens were responsible for 18 food-poisoning outbreaks over the last decade.

Greens are washed by commercial processes before they head to the grocery store. But these methods, which can include water and bleach rinses or irradiation, are not completely effective, says Nichola Kinsinger, Ph.D. She says scientists have estimated that 99 percent of food-borne illnesses from leafy greens can be traced back to disinfection issues. As a result, they have searched for and developed a different approach to attacking the bacteria, most notably E. coli, which is the cause of many outbreaks.

“Despite current disinfection rinsing, bacteria are surviving on the leaf and causing cross contamination, resulting in the numerous outbreaks we hear about in the media,” Kinsinger says. She is a postdoc in the lab of Sharon Walker, Ph.D., at the University of California, Riverside. “Pathogens can come from irrigation waters or from water used during processing, and they can adhere to spinach leaves. If these bacteria are not all killed in the disinfection process, they can continue to live, grow, spread and contaminate other surfaces within the facility and other leaves.”

Using a parallel-plate flow chamber system that Walker developed, the researchers tested the real-time attachment and detachment of bacteria to the outer layer of spinach leaves. At low bleach concentrations, the bacteria fell off the leaves, but remained alive. At the higher concentrations used commercially, however, all of the bacteria were killed. “This result was perplexing,” Walker says. “Our experiments were telling us that commercial bleach rinses should be much more effective than they are. But then we studied the leaf itself in more detail.”

A spinach leaf is not perfectly smooth, she notes. So, the team modeled how the bleach would move across the surface of a spinach leaf, taking its bumps and grooves into account. Surprisingly, the model revealed that the concentrations of bleach on leaves may not be consistent.

“We found that because of the topology of the spinach leaf, nearly 15 percent of the surface may ‘see’ a bleach concentration that is 1,000-times less than that of the rinse solution,” Kinsinger says. In some cases, that translated to a 90 percent bacterial survival in their tests—and a high risk for cross contamination.

To reduce that risk, the researchers are optimizing an inexpensive titanium dioxide (TiO2) photocatalyst that companies could add to the rinse water or use to coat equipment surfaces that come into contact with the leaves as they are processed. When TiO2 absorbs light, it produces a strong oxidant that kills bacteria.

The scientists now plan to conduct more studies on the photocatalyst, and they will look at a broader range of foods, engineered surfaces and pathogens.

Bacterial occurrence in kitchen hand towels

Posted on August 31, 2014 by Douglas Powell

People don’t use dryers much in Brisbane. It hardly rains, so people use clotheslines, and electricity is expensive.

And it’s so natural.

My clothsline can usually be found with an abundance of hand (or tea) towels.

I use them all the time when cooking and am fastidious about washing them.

I also wonder how often those cook aprons are washed.

Gerba et al. report the common occurrence of enteric bacteria in kitchen sponges and dishcloths suggests that they can play a role in the cross-contamination of foods, fomites and hands by foodborne pathogens. This study investigated the occurrence of bacteria in kitchen towels often used to dry dishes, hands and other surfaces in the domestic kitchen. A total of 82 kitchen hand towels were collected from households in five major cities in the United States and Canada and the numbers of heterotrophic bacteria, coliform bacteria, and Escherichia coli in each towel were determined. In addition, identification of the enteric bacteria was performed on selected towels. Coliform bacteria were detected in 89.0% and E. coli in 25.6% of towels. The presence of E. coli was related to the frequency of washing.

5 Things Everyone Should Know About Washing Food (via Quest)

Posted on August 14, 2014 by Ben Chapman

My friend, Matt Shipman, a science writer and public information officer at North Carolina State University writes in the below Quest North Carolina post about washing food (reprinted with permission):

Everybody eats, and no one wants to eat something that could make you sick. But there’s a lot of misinformation out there about how and whether you should wash your food.

Food safety is an important issue. The U.S. Centers for Disease Control and Prevention estimates that each year one in six people in the United States will get sick because of food-borne illness. And risks can be increased or decreased at every point between the farm and your fork. Yes, you want to make sure to cook your food to the appropriate temperature, but here are some other tips to help you make good decisions in the kitchen.

1. Don’t Wash Meat

Some people think that you’re supposed to wash chicken, turkey, or other meats before cooking. Those people are wrong. “Research shows that washing meat can spread dangerous bacteria around your kitchen or food preparation area,” said Ben Chapman, a food safety researcher at North Carolina State University. “And washing poultry under running water can spray surface contamination up to three feet away. We cook meat to make it safer; washing meat can only make a meal riskier.”

2. Washing Fruits and Veggies Only Removes up to 99 Percent of Pathogens

“That seems good, but it’s not great,” Chapman said. By comparison, cooking food can cut the number of bacteria or other microbial pathogens by 99.9999 percent. And that 0.9999 percent difference can be important. If a food is contaminated by thousands of microbes, washing off 99 percent means that dozens will be left behind — and that’s enough to make you sick. That is why people who are immunocompromised, such as some chemotherapy patients, are often discouraged from eating raw fruits and vegetables.

3. Don’t Use Soap

“Although washing has its limitations, vigorously rinsing produce under running water is the most effective way to remove the microbes that cause foodborne illnesses,” Chapman said. You don’t need to use soap or special cleaning solutions. In fact, using soap can actually introduce additional risk, because soaps may contain chemicals that aren’t intended for human consumption.

4. You Can’t Get All the Pesticides Off Your Food (but Don’t Panic)

Some minute traces of pesticide will probably be on — or in — your fruits or vegetables when you eat them. “But being able to detect a pesticide doesn’t mean that it’s a public health problem,” said Chris Gunter, a researcher at NC State who studies vegetable agriculture. That’s because, after using a pesticide, farmers are required to wait for a specific period of time before harvesting (it’s called a “pre-harvest interval”). During that time, the pesticide breaks down or washes off, meaning any residual pesticide meets EPA’s human health requirements.

5. Even Organic Food Can Use a Rinse

Just because produce is labeled “organic” doesn’t mean that it’s somehow immune to microbial contamination. Organic farmers usually grow their fruits and vegetables in open fields, just like conventional farmers, and are subject to some of the same risks, such as fecal contamination from wildlife (that is, poop can still get on the food).

“Any time you’re going to eat fresh produce you should rinse it off, if for no other reason than to rinse off dirt,” said Don Schaffner, a food safety researcher at Rutgers. “And rinsing off produce may offer some risk reduction in terms of microbial pathogens.”

Bonus: Don’t Wash Pre-Washed Veggies

If you’ve bought salad mix that is labeled as “pre-washed,” you really don’t need to wash it again, Schaffner said. In fact, you probably shouldn’t wash it again. “An expert panel reported in 2007 that consumers who wash these salads again won’t reduce the risk,” Schaffner said, “and may actually create a risk of cross-contamination” where pathogens from other foods get onto the salad. In this case, being lazy is a virtue.

The limitations of washing fresh produce at home

Posted on June 8, 2014 by Ben Chapman

A couple of weeks ago my friend Matt Shipman, who runs The Abstract, asked me to answer a question about the best way to wash produce in the home.

I’ve received different iterations of this question up from extension agents, media and at Food Safety Talk with Don Schaffner. I’ve sort of settled on this: use water, vigorously running out of the tap, but don’t expect washing to make your produce risk-free.

I used to say that washing in the home did nothing for food safety but Don, the smart math dude I hangout with electronically, reminded me that saying it does nothing is incorrect – it does something.

Just not as much as folks may expect.

Matt captured the discussion for a blog post, below.

Here’s the question we got: “What is the most effective means of cleaning fresh produce at home to remove micro-organisms that could make you sick?”

“Vigorously rinsing the produce under running water is the most effective way of removing the microbes that cause foodborne illnesses – you don’t need soap or any special cleaning products,” says Ben Chapman, a food safety researcher at NC State. “But while washing your produce may remove some pathogens, it doesn’t eliminate risk altogether.”

“At best you get a two log reduction – that’s a 99 percent reduction in microbes,” Chapman says. “That seems good, but it’s not great. While washing can help reduce pathogen contamination, it shouldn’t be relied on as the only control measure.”

By comparison, cooking food results in a six log reduction in viable microbes. That means the population of viable microbes gets cut by 99.9999 percent(!).

The difference between 99 percent and 99.9999 percent is important because some fruits and vegetables can be contaminated with thousands of microbes. And we know that, on average, most microbial food-borne illnesses are caused by foods that are contaminated by only 20-30 organisms (the mean infectious dose for some of the pathogens of concern -ben).

So washing off 99 percent of the microbes doesn’t help much if a food was carrying thousands of microbes to start with.

Buy from producers who know what the risks are and are employing strategies to reduce them. Ask lots of questions.

Some good references on how I’ve arrived at my answer are here: Bassett and McClure 2008; Parish et al., 2003; Parnell et al., 2005; Verrill et al., 2012. There are other good ones out there too including this fact sheet from Christine Bruhn and others.

No need to rewash pre-washed leafy greens; Academy of Nutrition and Dietetics misses the evidence-based message again

Posted on May 22, 2012 by Ben Chapman

My friends at the Academy of Nutrition and Dietetics are at it again. Last week they recycled a press release on the dangers of reusable bags that was full of holes, This week Sarah Kriegar of The Academy decided to remind folks that washing pre-washed leafy greens is a good idea.

“Fruits and vegetables are an important part of a healthy eating plan, and should fill half of your plate, but just like any food product, extra precautions should be taken to reduce the risk of food poisoning,” said Sarah Krieger, a registered dietitian and academy spokeswoman, in a statement.
She said (among other things -ben):

– Buy loose produce rather than pre-packaged, but if you do buy packaged lettuce or carrots or other items, wash them even if they say “ready to eat.”

I’d like to see what data The Academy has that shows this recommendation would result in risk-reduction.

Washing pre-washed leafy greens in the home isn’t going to accomplish further risk-reduction than what was applied at processing; tight attachment or internalization of the target pathogens are likely for whatever is left when it gets to someones kitchen.

A review paper published in Food Protection Trends in 2007 contained guidelines developed by a national panel of food safety folks and concluded:

"… leafy green salad in sealed bags labeled ‘washed’ or ‘ready-to-eat’ that are produced in a facility inspected by a regulatory authority and operated under cGMPs, does not need additional washing at the time of use unless specifically directed on the label.”
The panel also advised that additional washing of ready-to-eat green salads is not likely to enhance safety.

“The risk of cross contamination from food handlers and food contact surfaces used during washing may outweigh any safety benefit that further washing may confer."

A table of leafy green-related outbreak is available at http://bites.ksu.edu/leafy-greens-related-outbreaks. I’m not sure there’s any data out there that shows washing would have been a protective step for any of the outbreaks.

The merits of washing produce at home are debatable – many papers show somewhere around a 1-log reduction of pathogens from washing produce with no difference whether the fruit or vegetable was washed with water or some sort of sanitizer. A ten-fold reduction is okay if there isn’t much pre-home contamination, but washing as a kill step sucks and is really more about increasing quality(removing grit). Effective risk reduction actions for fresh produce are more likely found in production, processing and food service preparation (where contamination often occurs) – not in home kitchens.

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