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decisions about pathogen-reduction levels are
inherently arbitrary because they require guessing
the initial level of contamination. That guess can
be supported by the results of scientific studies
measuring the number of foodborne pathogens
present under the various conditions that cooks
encounter. But it’s still a guess.
Many people don’t realize that authorities rely
on guesswork to develop these standards. Chefs,
cookbook authors, and public health officials often
make dogmatic statements that food cooked to
a standard is “safe,” but food cooked less than the
standard is “unsafe.” That can never be literally
true. No matter what the standard is, if the food is
highly contaminated, it might still be unsafe
(especially owing to cross-contamination). And on
the other hand, if the food is not contaminated,
then eating it raw won’t hurt you.
All food safety standards deal in probabilities.
Reaching a higher standard (i.e., cooking food
longer or at a higher temperature) will make the
food less likely to be unsafe, and targeting a lower
standard will make it a bit more likely. But there
are no guarantees and no absolutes. Deciding what
level is enough is guesswork. There are no black
and white standards; there are only shades of gray.
To compensate for this inherent uncertainty,
food safety officials often base their policies on the
so-called worst-case scenario. They reason that if
you assume the absolute worst contamination
levels and act to address that threat, then the public
will always be safe. Setting relatively high D levels
to account for a worst-case scenario establishes
such a formidable barrier for pathogens that even
highly contaminated food will be rendered safe.
High D levels also offer a measure of insurance
against an imperfect thermometer, an unevenly
heated oven, an inaccurate timer, or an impatient
chef. If real-world conditions miss the mark,
slightly lower reductions will still suffice.
Not surprisingly, some food safety experts
challenge this conservative approach. The required
pathogen reductions or “drops” explicitly cited in
U.S. federal regulations, for example, range from
a 4D drop for some extended-shelf-life refrigerated
foods, such as cooked, uncured meat and poultry
products, to a 12D drop for canned food, which
must last for years on the shelf. General FDA
cooking recommendations for fresh food are set to
reach a reduction level of 6.5D, which corresponds
to killing 99.99997% of the pathogens present.
Many nongovernmental food safety experts
believe this level is too conservative and instead
consider 5D to 6D pathogen reduction for fresh
foods sufficient for real-world scenarios.
An expert advisory panel charged with reviewing
the scientific basis of food safety regulations in
the United States made just this point about
standards developed by the U.S. Department of
Agriculture (USDA) Food Safety and Inspection
Service (FSIS). In a 2003 report, the panel, assembled
by the U.S. Institute of Medicine and National
Research Council, questioned the FSIS Salmonella
reduction standards for ready-to-eat poultry and
beef products. In devising its standards, the FSIS
had established a worst-case Salmonella population
for the precooked meat of each animal species,
then calculated the probability that the pathogen
would survive in 100 g / 3.5 oz of the final readyto-eat
product.
In the case of poultry, for example, the FSIS
calculated a worst-case scenario of 37,500 Salmonella
bacteria per gram of raw meat. For the 143 g /
5 oz of starting product necessary to yield 100 g /
3.5 oz of the final, ready-to-eat product, that works
out to nearly 5.4 million Salmonella bacteria before
cooking. To protect consumers adequately, the
FSIS recommended a 7D drop in bacterial levels,
equivalent to a reduction from 10 million pathogens
to one.
The review committee, however, found fault
with several FSIS estimates that, it said, resulted
in an “excessively conservative performance
standard.” Even “using the highly improbable FSIS
worst-case figure,” the committee concluded that
the ready-to-eat regulation should instead require
only a 4.5D reduction.
The irony is that, although experts debate these
matters, their rigorous analyses can be undermined
by confounding factors such as crosscontamination.
Imagine, for example, that a
highly contaminated bunch of spinach really does
require a 6.5D reduction in pathogens to be safe.
Even if that spinach is properly cooked, it could
have contaminated other food or utensils in the
kitchen while it was still raw, rendering moot even
an extreme 12D reduction during the cooking
process. A chain is only as strong as the weakest link,
and in food safety, cross-contamination is often the
weakest link. One powerful criticism of food safety
standards is that they protect against unlikely
worst-case scenarios yet do not address the more
likely event of cross-contamination.
Another conservative tactic used by health
officials is to artificially raise the low end of
a recommended temperature range. Most food
pathogens can be killed at temperatures above
50 °C / 120 °F, yet food safety rules tend to require
temperatures much higher than that. Experts may
worry that relying on the low end of the range may
be dangerous for the same reasons that moderate
D levels cannot be trusted: vacillating oven
temperatures, varying chef temperaments, and so
on. Still, their solution belies the facts.
Factors Influencing Food Safety Trends
Scientific data, political and industry pressure, tradition, and
cultural factors are among the elements that can interact to
influence how food safety rules are made.
Simplification and rule making
Rules and regulations for professional chefs
For Our Own Good?
The public health goal of maintaining food safety
and minimizing harm poses an interesting dilemma:
when does the end justify the means? More
specifically, is it justifiable to promote unscientific
food safety standards in the name of public safety?
Regulators seem to act as if it is.
During a recent outbreak of Escherichia coli
linked to contaminated fresh spinach in the
United States (see The E. Coli Outbreak of 2006,
page 172), public health authorities initially told
consumers, retailers, and restaurants to throw out
all spinach, often directly stating in public announcements
that it could not be made safe by
Scientific data on pathogens
Allowance for safety factors
Traditional and cultural factors
Political and industry pressure
Extreme simplification
Recommendations for consumers
168 VOLUME 1 · HISTORY AND FUNDAMENTALS
FOOD SAFETY 169