Thought this might interest those of you with dairy connections. From
ProMED. It's a review of and response to the Anti-Dairy Coalition's
claim that pasteurization does not kill Mycobacterium
paratuberculosis. I believe it's a pretty good case study of how
complicated is the relationship between research and people's
understanding of that when basing their food consumption decisions
on the best available research. And how easy it is both to
misunderstand and be misunderstood that relationship.
MYCOBACTERIUM PARATUBERCULOSIS, MILK SURVEY - UK (02)
A ProMED-mail post
Date: Wed, 12 Aug 1998 13:14:31 GMT
From: J Ralph Blanchfield
What may have sparked off the current investigation, requested by
ACMSF, was the following press release in USA in July.
ANTI-MILK GROUP EXPOSES CLAIM THAT NORMAL PASTEURIZATION KILLS
DANGEROUS BACTERIUM IN MILK July 14/98
NEW YORK -- The Anti-Dairy Coalition has denounced a claim, based on a
recent U.S. Department of Agriculture (USDA) study, that normal
pasteurization practiced by dairy producers nationwide inactivates a
dangerous bacterium routinely found in raw milk.
In his weekly Anti-Dairy Coalition Newsletter column on the Internet,
Coalition executive director Robert Cohen says the USDA study, which
was reported in the May 10, 1998 issue of Hoard's Dairyman, a trade
publication, has been completely misrepresented by the agency and by
the Food and Drug Administration (FDA) in claiming that normal
pasteurization (72 degrees centigrade for 15 seconds) destroys
_Mycobacterium paratuberculosis_, the bacterium linked to Johne's
disease in cows and Crohn's disease in humans that produces persistent
and severe diarrhea.
Cohen, author of "Milk - the Deadly Poison," says that the USDA study
actually revealed that the dangerous bacteria were not totally
inactivated until after 15 minutes of pasteurization at 72 degrees
centigrade. That's "very bad news for all milk drinkers," says Cohen.
"Normal pasteurization at this temperature calls for only 15-second
treatment, not 15 minutes. We believe the government and Hoard's
Dairyman are misleading the public into thinking pasteurized milk is
safe from _Mycobacterium paratuberculosis_ when the USDA's own
scientist is saying that pasteurization inactivates the bacterium only
when the process maintains at least 72 degrees centigrade for at least
15 minutes. That's 14 minutes and 45 seconds longer than the normal
commercial pasteurization of milk in the United States."
The USDA study is entitled "Heat Inactivation of _Mycobacterium
paratuberculosis_ in Raw Milk: Are Current Pasteurization Conditions
Effective?" Based on this study, Hoard's Dairyman told its
100,000-plus milk producer subscribers, "Heat treatment
(pasteurization) destroys this dangerous disease."
Cohen says the FDA supports the same conclusion. He refers to a letter
addressed to government officials from Joseph Smucker, team leader of
the Milk and Safety Team at the Center for Food Safety and Applied
Nutrition, a branch of the FDA. The letter says: "After a review of
the available literature on the subject, it is the position of FDA
that the latest research shows conclusively that commercial
pasteurization does indeed eliminate this hazard."
Cohen says every assertion about pasteurization's effectiveness is
refuted in the abstract of the USDA study, which states: "Currently,
it is not known whether commercial pasteurization effectively kills
_Mycobacterium paratuberculosis_ in contaminated raw milk." "This
sentence," Cohen says, "contradicts every conclusion made from this
very same paper!"
The senior author of the abstract is Judy Stabel, Ph.D. On the second
page of Dr. Stabel's paper (published in the December 1997 issue of
Applied and Environmental Microbiology), she reveals: "Bacteria were
not totally inactivated until after 15 minutes of incubation
(pasteurization) at 72 degrees centigrade." In her paper, Dr. Stabel
also writes: "There is no definitive evidence to date that viable M.
paratuberculosis is present in retail pasteurized dairy products."
When she was asked why there was no evidence and if milk samples had
ever been tested at retail sites, Cohen says her response was "No."
When asked "Why not?" she replied, "I don't know." However, Cohen
contends that British scientists have taken milk samples at the point
of retail purchase and have cultured live tuberculosis [presumably she
means _M. paratuberculosis_ - MHJ] bacteria from these samples.
Cohen concludes that the FDA and USDA have misinterpreted Dr. Stabel's
paper, and scientific evidence suggests that this dangerous bacterium
survives pasteurization. "This is just another example of how
Americans are being betrayed by regulatory agencies like FDA and
USDA," Cohen warns.
Formed in June 1998, the Anti-Dairy Coalition includes some of the
country's top physicians and health educators: Dr. Julian Whitaker,
author and editor of the monthly newsletter, Health & Healing; Dr.
Charles Attwood, often called heir apparent to Dr. Benjamin Spock; Dr.
Vicki Griffin; Dr. Daniel Twogood; Dr. Richard DeAndrea and Dr.
However, the following information was subsequently provided by IFT to
its Science Communicators by e-mail, and I received a copy as part of
the mutual exchange of food safety information between IFST and IFT --
It appears that the Anti-Dairy Coalition ignored results from the
second half of Stabel et al. (1997). The researchers examined the
effectiveness of two methods of heat inactivation to inactivate
_Mycobacterium paratuberculosis_ in raw milk:
(1) the holder test tube method, often used in previous studies but
not used commercially, in which the milk is held still during
(2) the lab-scale pasteurizer method, which simulates
high-temperature, short-time (HTST) conditions in commercial
pasteurization and in which the milk flows through the pasteurization
Stabel et al. concluded that the flow of milk during commercial
pasteurization is essential for effective killing of the _M.
paratuberculosis_. Effective pasteurization via the non-commercial
holder test tube method did, indeed, require 15 minutes at 72degC. The
researchers stated: "Bacteria were not totally inactivated until after
15 min of incubation [via the holder tube method of pasteurization] at
72degC." These are the results reported, perhaps not in sufficient
detail, by the Anti-Dairy Coalition.
The latter commercial method, however, did effectively kill the
bacteria within 15 seconds. The researchers state: "Results from _M.
paratuberculosis_ heat inactivation experiments when the lab-scale
pasteurizer method was used indicated that both strains of _M.
paratuberculosis_ tested, 19698 and Ben, at a concentration of either
10^4 or 10^6 CFU/ml were effectively inactivated after treatment at
72degC for 15 s (data not shown)."
The authors write:
"Studies conducted in our laboratory with the lab-scale industrial
pasteurizer unit have demonstrated that turbulent flow of milk during
pasteurization is essential for complete killing of contaminating _M.
Also of interest is a Letter to the Editor, charging that Stabel et
al. dismissed previous work which concluded that HTST pasteurization
may not effectively kill the bacteria. The letter also questioned the
use of frozen and _sonicated M. paratuberculosis_.
In a rebuttal, Stabel wrote: "In our opinion, the laboratory-scale
pasteurizer unit utilized in our laboratory simulates commercial
pasteurizer units more closely than any other methodology employed to
date. Results from our studies with the laboratory-scale pasteurizer
indicate that HTST pasteurization effectively kills all _M.
paratuberculosis_ cells experimentally inoculated into raw milk."
Stabel, J.R., E.M. Steadham, and C.A. Bolin. 1997. Heat inactivation
of Mycobacterium paratuberculosis in raw milk: Are current
pasteurization conditions effective? Applied and Environmental Micro.
Grant, I.R. 1997. Letter to the Editor. And author's reply. Applied
and Environmental Micro. 64(7): 2,760-61.
The UK requirement of 71.7 degrees C for 15 seconds or any equivalent
combination [UK Dairy Products (Hygiene) Regulations 1995 (Schedule 4,
Part II, 2(a)] are only very slightly less than the US requirement of
72 degrees C for 15 seconds.
Can that marginal difference account for the preliminary finding of a
few commercial samples in N Ireland containing _M. paratuberculosis_?
Or do the results suggest either that not all plants there are
effectively complying all the time with the process required by the UK
Regulations, or that in those instances post-pasteurisation
contamination has occurred?
It seems to me that important immediate requirements must be to trace
the positive samples back to the plant(s) whence they came and to
investigate the equipment, the processing records and the plant
J Ralph Blanchfield, MBE
Food Science, Food Technology & Food Law Consultant
Chair, IFST External Affairs
Web Editor, Institute of Food Science & Technology
Michele Gale-Sinex, communications manager
Center for Integrated Ag Systems
UW-Madison College of Ag and Life Sciences
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