There’s a hot mess of a story about lettuce in the UK’s Daily Mail this weekend, that seems to capitulate between pre-packed lettuce and head lettuce, which have different consumer washing requirements for safety.

The story also leaves the impression that food safety lies with consumers and that washing does a lot.

Washing does a little.

Preventing or limiting contamination on the farm is far more important, especially for produce.

The Daily Mail story begins, “It is there on every packet of salad: ‘wash before eating’. But how many of us will simply rip open the wrapping and empty the contents into a salad bowl, or tear it into a sandwich without a second thought?

“Doing so could yield unpleasant results, says the Food Standards Agency (FSA), the Government’s advisory body.”

The Mail on Sunday conducted a special investigation – and discovered food-poisoning bacteria could be present in one in 20 lettuces in some supermarkets.

We bought 120 whole lettuces, all British-grown, including little gem, round and cos, purchasing 20 from each of six different supermarkets: Waitrose, Marks & Spencer, Tesco, Sainsbury’s, Morrisons and Asda.

All the lettuces were taken to a food-testing laboratory and screened for Listeria monocytogenes and E.coli.

Of the 120 lettuces we tested, three were contaminated: 2.5 per cent, or one in 40.

A Morrisons lettuce contained 20 cfu/g, while one from Waitrose contained 490 cfu/g.

Of the high E.coli reading, a Waitrose spokesperson comments: ‘While we strictly enforce the highest hygiene standards at all farms supplying us, we would always recommend people follow Government advice and wash all produce.’

A spokesman for Morrisons said: ‘There’s nothing here to be concerned about but we recommend all customers follow the FSA’s recommendation that all lettuce be washed.’

Nothing to be concerned about; move along. But there is a difference between pre-packaged and other kinds of lettuce.

Bob Martin, a microbiologist at the FSA, seems to get it, when he says , “Most produce in the shops is deceptive because it looks clean. But unless it’s labelled ‘washed and ready to eat’ it must always be thoroughly washed.”

Washing pre-washed leafy greens in the home isn’t going to accomplish further risk-reduction than what was applied at processing.

A review paper published in Food Protection Trends in 2007 contained guidelines developed by a U.S. national panel of food safety types 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 reduced risk in any of those outbreaks.