Science Questions

Is there a reliable way to make salad vegetables safe without cooking them?”

Sat, 11th Jun 2011

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Andrew Reitermeyer, facebook asked:

Is there a reliable way to make salad vegetables safe without cooking them? I live near the region of the EHEC outbreak and would like to eat salad vegetables but in a safe manner.


Karen -   A good question.  I mean, the really important thing about the EHEC is that it requires very, very few bacteria. If your food is contaminated then you basically have to bleach it to get rid of them and make it really safe. We really don't want to do that because the toxins and the bleach would be harmful in themselves.  Washing as thoroughly as possible as well, and hoping I suppose. I mean, that's a really difficult question because as you say, you can't cook salad vegetables, and you don't necessarily not want to eat them because of the chances of them being contaminated. As long as they're not from a source where this contamination has been found the risk is actually quite low.  I don't know the answer to that question.

Chris -   Because when people make motorway service station sandwiches and things like that, the salad in these pre-prepared sandwiches has already been washed in a weak solution of bleach, hasn’t it? And I guess the problem with these bugs is if they get into small imperfections in the surfaces of the vegetable, so little nooks and crannies there, the bugs can lurk. The infectious dose is so low, it’s just a handful of organisms at most that actually cause disease, and as you peel it, boil it, or leave it, then you're pretty likely to get it.

Karen -   I mean, that's exactly right.  Yeah, I mean, even washing them in a weak bleach as you say, they'll be lurking.  If they're there, they can lurk right down in bits that will not be penetrated by the bleach and you still eat them.  Yes, 6 to 10 will actually cause an infection of these particular bacteria.



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One should be very specific that this is Sodium hypochlorite bleach, also known as Chlorine Bleach.
Don't consider the non-chlorine bleaches as being equivalent.

And if using bleach as a disinfectant, do not mix it with anything else.  No acids, bases, vinegar or ammonia as it can cause a bad reaction.

It is not a bunch of chemicals, but one very specific chemical, Sodium hypochlorite (NaClO).

Chlorine Bleach has been used as a disinfectant including a drinking water disinfectant, so it should be reasonably safe in small quantities.  And, I assume the salad is rinsed well after using the chlorine rinse.

However, many people try to reduce their free radicals.  Sodium hypochlorite would likely increase the free radicals.

Another thought.
What about soaking your salad in concentrated vinegar for a couple of minutes.
Perhaps Rinse it off just a second.
Add olive oil

However, I'm seeing more anecdotal notes than scientific evidence for the use of vinegar as a disinfectant.  It has been used in canning for ages though.

Ethanol would also make a good disinfectant.

The primary source of the bacteria is on the surface.
There was a tomato scare in the USA earlier.
Mom always liked to skin the tomatoes by briefly dipping them in boiling water, then pulling off the skins.  Doing so should effectively eliminate the risk of Enterohemolytic E-Coli in the tomatoes.  Unfortunately lettuce isn't treated in the same fashion.

The best way to prevent E-Coli though.
Grow your own vegetables. 
And, I suppose also beware about manure fertilizers.  Notes indicate that high temperature composting of the manure will destroy the E-Coli.
CliffordK, Tue, 14th Jun 2011

Am I right in thinking that washing the vegetables in mild bleach will only help with secondary contamination due to contact with bacteria after harvesting, and that vegetables grown in a contaminated environment have internal contamination? Geezer, Wed, 15th Jun 2011

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