Modernist-Cuisine-Vol.-1-Small

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Roundworms, such as this female
Trichinella, are among the few foodborne
pathogens that naturally exist inside intact
meat or fish.
PAR ASITIC WOR MS
Fear of Trichinella spiralis, perhaps the most
infamous foodborne worm, has inspired countless
overcooked pork roasts. The trichina is widely
dreaded for its ability to burrow into the muscles
of pigs and other livestock, inflicting people who
eat the contaminated meat with the disease
trichinellosis (also called trichinosis). Most of us
learned of the danger from our mothers as well as
from some public health authorities and nearly all
cookbook authors, who have insisted for years that
pork should always be cooked well-done.
Yet in reality the Trichinella roundworm has
little impact on either the number or severity of
foodborne disease cases in the United States.
A CDC surveillance report that covers the years
1997–2001 confirms that physicians have seen
case loads associated with eating pork plummet:
of 55 cases in which people developed symptoms
of trichinellosis, investigators could link only
eight to commercial pork products purchased in
the U.S. Most of the few dozen other cases
resulted from eating the meat of wild game
bears in particular, but also boars and mountain
lionsor pork obtained directly from farms or
home-raised pigs, to which industry standards
and regulations do not apply (see Misconceptions
About Pork, page 179).
Although concern about foodborne worms can
be overblown, no one wants to harbor parasites
that can stick around for years or even decades.
So all cooks should know some basic facts about
the parasitic roundworms, flukes, and tapeworms
that sometimes make their way into the food
supply.
The diversity of these organisms is underappreciated.
Beyond Trichinella and other roundworms
or nematodes, foodborne worms of note include
flukes (trematodes) and tapeworms (cestodes). In
general, these parasites produce disease through
two main mechanisms: the worms either penetrate
body tissue during invasive infections, or
they live in the gut as noninvasive infections.
How Trichinella Can Get into Meat
An invasive infection by worms, typified by the Trichinella life cycle, begins
when an animal consumes muscle tissue that contains encysted worm
larvae. Freed from the tissue by the new host’s digestive process, the larvae
rapidly mature into male and female adults, which mate and release new
larvae. Each larva burrows into a muscle cell, converting it into a so-called
nurse cell by secreting proteins that promote the formation of blood
1
Life stages
Larvae burrow into animal
muscle and form cysts.
When ingested by another animal,
larvae leave cysts and travel to the
small intestine, where they mature.
Adult worms reproduce and
release new larvae.
2
Contamination
Pigs, wild boar, bear, and other
animals get infected with parasites.
vessels. Blood vessels then grow around the larva and feed it. Larvae can
live in protective calcified cysts for years until the host dies and is eaten,
which starts the cycle anew in another host.
Trichinella worms can survive refrigeration, but sufficient freezing will kill
the worms in pork. For other meats, and as an alternative for pork, safe
cooking practices will render any worms in the food harmless.
3a
3b
Unsafe storage
Fresh meat is refrigerated,
but parasites survive.
Contamination risk
Low High
Wild game
Pork
Safe storage
Fresh pork can be frozen to
−20.6 °C / −5 °F for 82 h or to
−37.2 °C / −35 °F for ½ h, killing all
parasites. All parasites may not be
killed in boar or bear meat, however.
4b
Unsafe cooking
4a
Meat is insufficiently cooked
(either too quickly or at too low a
temperature), leaving viable parasites.
Contamination risk
Low High
Wild game
Pork
Safe cooking
Meat is cooked to 54.4 °C / 130 °F
for 112 min or 60 °C / 140 °F for 12 min,
killing all parasites.
Contamination risk
Low High
Wild game
Pork
Contamination risk
Low High
Wild game
Pork
Contamination risk
Low High
Wild game
Pork
Roundworms
Flesh-burrowing roundworms are among the few
pathogens that normally live inside human food,
typically buried deep inside the muscle tissue of
domestic pigs as well as wild boars, bears, and
other carnivorous animals. One Trichinella
subspecies that lives in polar bears and walruses
has been linked to outbreaks among Inuit communities
near the Arctic Circle.
With few exceptions, Trichinella infections do
not cause death, although they can cause serious
cardiac or neurological complications if they enter
the heart or brain. Once the larvae invade tissue,
they wait patiently for the host to die. In the wild,
dead animals are invariably eaten by scavengers,
which gives trichinae a chance to propagate.
One way to prevent trichina worms from
infecting livestock is to cook farm slops or feed
that contains meat scraps before giving it to pigs.
In the kitchen, however, killing trichinae does not
require the excessive heat that most people
imagine. The FDA Food Code recommends using
the same time-and-temperature combinations for
cooking pork as it does for cooking beef or lamb
(for example, 54.4 °C / 130 °F for 112 minutes or
60 °C / 140 °F for 12 minutes). U.S. Government
regulations for killing trichinae specify even lower
values: 54.4 °C / 130 °F for 30 minutes or 60 °C /
140 °F for one minute.
So why did Mom think she had to cremate the
pork roast? Well-meaning public health authorities
have long exaggerated both the threat of
120 VOLUME 1 · HISTORY AND FUNDAMENTALS
MICROBIOLOGY FOR COOKS 121