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Re: Organic/E.coli "Connection" in SF Ex/Chron
lhom@nature.berkeley.edu (Louis Hom) wrote:
>I noticed a piece in the Sunday San Francisco Examiner/Chronicle a rather
>heated (and, I'd add, a bit annoying) attack on unpasteurized juices and on
>the use of organic fruits in making these juices. I know that debunking
>the "link" between fertilizing with manure and E.coli contamination
>(especially in reference to some accusations in Connecticut(?)) has been a
>topic of interest to at least some of the folks in these newsgroups. I'd
>recommend/request that someone more knowledgeable than myself take a look
>at the article and write a response that is more informed than that of the
>original author. I hope that was at least moderately clear.
I haven't seen the S.F. Examiner piece you speak of, but the reason
manure, specifically cow manure, has been implicated is because to
date, cows are the only known carrier of serotype 0157:H7. This is not
to say that other carriers don't exist but aren't known yet, or that
some type of cross contamination couldn't have occurred. I suspect
this is/will be an area of a great deal of study.
> Oh, and one other thing -- if I read him correctly, the author was
>suggesting that the bacteria would grow faster in more acidic juices, which
>seems to be just plain backwards to me. Comments?
In an article by Dr. Peter Feng of the F.D.A. entitled "Escherichia
coli serotype 0157:H7: Novel Vehicles of Infection and Emergence of
Phenotypic Variants ." , Dr. Feng specifically mentions in the U.S.
Food Code of the F.D.A. "Foods with a pH value of less than 4.6 are
generally regarded as low risk in terms of food safety. However
several recent outbreaks attributable to serotype 0157:H7 have shown
that this pathogen can persist in foods with low pH."
In a case dating from 1991, 23 people in were affected by a batch of
cider made from unwashed "dropped" apples. The implicated cider had a
pH value of 3.7 to 3.9. The article states that "several laboratory
studies have subsequently demonstrated that isolates of serotype
0157:H7 can tolerate acidic conditions."
I wonder if the author of the Examiner piece was confusing the pH
issue with the temperature issue. In "Fate of enterohemorrhagic
Escherichia coli O157:H7 in apple cider with and without
preservatives." by T. Zhao, M. P. Doyle & R. E. Besser of the Center
for Food Safety and Quality Enhancement, University of Georgia,
Griffin 30223.
"A strain of enterohemorrhagic Escherichia coli serotype O157:H7
isolated from a patient in an apple cider-related outbreak
was used to study the fate of E. coli O157:H7 in six different lots of
unpasteurized apple cider. In addition, the efficacy of two
preservatives, 0.1% sodium benzoate and 0.1% potassium sorbate, used
separately and in combination was evaluated for antimicrobial effects
on the bacterium. Studies were done at 8 or 25 degrees C with ciders
having pH values of 3.6 to 4.0. The results revealed that E. coli
O157:H7 populations increased slightly (ca. 1 log10 CFU/ml) and then
remained stable for approximately 12 days in lots inoculated with an
initial population of 10(5) E. coli O157:H7 organisms per ml and held
at 8 degrees C. The bacterium survived from 10 to 31 days or 2 to 3
days at 8 or 25 degrees C, respectively, depending on the
lot. "
I read this to say that the cooler you keep the product, the longer
the organism can survive. Although there are other spoilage
considerations, from an E. coli standpoint this is the opposite of
what you would assume might be the case.
Hope this is helpful.
Regards,
Jonathan
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Jonathan Bishop Bishop's Orchards
B.W. Bishop & Sons, Inc. Growers of Fine Fruit
Guilford, Connecticut since 1871
E-Mail:j_bishop@ix.netcom.com
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