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  • From: KAKerby AT aol.com
  • To: market-farming AT lists.ibiblio.org
  • Subject: Re: [Market-farming] GAP summary (long)
  • Date: Tue, 16 Mar 2010 14:26:39 EDT

For the first question, sadly, warmer temps can help E coli zoom along very happily, but cold weather doesn't kill it.  It just goes into a sort of dormancy.  As soon as temps hit that optimum point again, it wakes up and keeps on' truckin'.  Unfortunately, that's true whether it's cold in the soil, or cold in the fridge/cooler/cold storage.  The longevity in the soil was measured during the growing season in a temperate plot, but I'm not sure what zone it was.  I can go back and look in that particular report where they did the study.  I'll try to remember to do that and let everyone know.  I'll also try to remember to ask them sometime whether overwintering changes the day count (in either direction), or if extended freezing would shorten that lifespan, even though short-term freezing apparently has no effect. 
 
As for having the contamination actually being in the produce, that was one of my specific questions - is there uptake via the roots and/or stomata?  There is limited and often non-repeatable instances of E coli being taken up into the plant.  When I say non-repeatable, that means one study found it happening on a limited basis but they couldn't duplicate it again even under similar circumstances.  So it's possible, but it doesn't happen very often.  It's rare enough that for guideline purposes, they don't worry about that per se.  The major screaming exception to that statement is that E coli can readily get into plant tissues in the case if tissue injury.  Even though the E coli doesn't pervade the plant very far, those localized tissues have huge concentrations of the E coli and at that point cannot be readily washed off.  The tissues are just too rough, and the E coli concentrations too high, to ever get it "clean".
 
For consumers washing produce, sadly most consumers quit too early, and/or are not thorough enough, to do a suitable job of removal for anything more than the largest particles of soil.  Even small insects can generally hang on for the ride, let along bacteria that can snuggle down real close to that leaf surface.  One of the demonstrations we did (not in the GAP class but in another class) was to use simple hand cream, impregnated with little glitteries that only show up under UV light.  We were then told to go wash our hands.  This was just standard hand cream on skin - nothing special.  After we washed our hands, we then put our hands under the UV light to show all the little nooks and crannies we'd missed.  That was a pretty sobering demonstration.  Each of those little glitteries could have been colonies of bad guys.  So washing is often recommended, but that's often too little to take care of any hitchhikers.  Combine that with E coli going dormant in the cooler, but waking up in warmth (ie, body temperatures), and the little buggers are just really hard to get rid of once they latch on.  Hence, the guidelines favored prevention over rinsing/washing after contamination had already occured. 
Kathryn Kerby
Frog Chorus Farm
Snohomish, WA
 
In a message dated 3/16/2010 10:59:37 A.M. Pacific Daylight Time, caverdjmoore AT hotmail.com writes:

First, thank you very much for sharing . . . the amount of research time you have saved me is invaluable.

Just a couple questions/points which may have already been brought up:

> But strong research results are coming in that indicate that separation time
> should be increased to 200 days where possible because E coli continues to
> live in soil for much longer than anyone expected. This seems to be the case
> regardless of how the soil is managed.

Would not the zone one lives in have an effect on this? I would think E coli living somewhere hot and muggy most of the time would live and multiply more than somewhere with very frigid winters.

Comment 2: I have read that E coli and the like is now turning up *inside* of produce but for outside issues, why don't consumers wash their produce? I only have one friend who does (OK, my kids all know better too), whoever deemed that produce doesn't need to be washed before eating? *sigh*

Again, I really enjoy the sharing on this list........

DebM
zone 5
www.sycamorecircle.com
                     
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