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| In the early 1800s, the British Navy needed unbreakable canned goods for sea
voyages, which spurred the development of tinned cans. By the 1860s, the production
of tinned goods was a booming industry in the United States. |
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List of Terms: P
(Return to Comprehensive List of Terms)
> Packaging
Wrappers or containers used to protect food from dirt, germs, and damage. Packaging
also keeps oxygen out and increases the shelf life of food.
Food Safety Implication: Packaging techniques use heat to kill pathogenic
bacteria or other methods, such as placing food in sterile packaging, to protect
food from micro-organisms that could cause spoilage or food-borne illness. Also,
since bacteria thrive on oxygen, some types of packaging reduce the amount of
oxygen available to bacteria to slow bacterial growth and extend the storage life
of the food. Labels on product packages also provide information about how to
safely use the product.
Food Safety Precautions:
- Always read the label on retail packaging. Handling, storage, and cooking
procedures can differ greatly for every product, and proper handling can ensure
product safety.
- Check the expiration, "sell by," and "use by" dates stamped on the package,
and don't take risks by using old products.
- Don't buy or use foods whose packaging has been broken, torn, or damaged.
Types of Packaging Commonly Used Today Include:
- Shelf-Stable Packaging - Traditional shelf-stable packaging consisted
of cans or glass jars. The newest shelf-stable packaging uses plastic containers.
So, instead of opening a can of soup or stew, pouring it into a pan and heating
it, you can pull a plastic soup package off the shelf and pop it into a microwave.
Such products can be safely stored on the shelf without refrigeration. Assuming
there are no breaks or tears in the package, these products should maintain top
quality for more than a year.
- Packaging That Requires Refrigeration
- Sous Vide (a French phrase for "under vacuum") - With this method,
fresh raw ingredients or partially-cooked ingredients are vacuum-sealed in a plastic
pouch. The pouch is heat-processed, then quickly chilled and transported under
refrigeration. Sous vide products must be kept refrigerated. Like other
vacuum-packed products, sous vide products will last 3 to 4 weeks refrigerated.
To serve, you simply heat the bag in boiling water.
- Vacuum Packaging (a.k.a. Modified Atmosphere Packaging) - Oxygen in
the package is mixed with a gas (normally carbon dioxide and/or nitrogen) that
slows spoilage, discoloration, and the growth of harmful bacteria. Vacuum packages
now include raw pork tenderloin, fully-cooked roast chicken, tuna spreads, and
tortellini. Some foods may require additional cooking or heating before serving,
so always check the label.
Common Types of Packaging Materials Include:
- Aluminum - Bottle caps and easy-to-open tops for cans.
- Glass Containers - Durable, chemical-resistant, can be kept highly
sanitary, and are ideal for the storage of solid and liquid foods.
- Cardboard - Comes in a variety of shapes and sizes and serves as containers
for food.
- Plastic - Has been used extensively as a shipping material for liquids
and perishable foods because of its high durability and insulation qualities.
- Tin-Plated Steel Cans - Used predominantly for food storage.
> Parasite
A plant or animal that lives on or in another plant or animal, while making no
beneficial contribution to that host.
Cryptosporidium, a parasite, can cause a
severe, life-threatening disease, particularly in
patients with AIDS.
Food Safety Implication: Food can become contaminated with parasites.
Some parasites have an indirect life cycle. For example, they need an intermediate
host (the food species) where they develop into a stage that is infectious to
humans. Humans that consume the infested food, either raw or undercooked, become
infected.
In parasites that are directly infectious, the parasite is physically transferred
by the food through contamination with a human or other host waste.
Some Examples of Parasites That May Contaminate Food Are: Trichinella
spiralis (trichinosis), which can be found in pork and Anisakis roundworm,
which can be found in fish. For more about other common parasites, see Cyclospora,
Cryptosporidium, and Toxoplasma
gondii.
> Partnership for Food Safety Education (see Fight
BAC!TM Campaign)
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Louis Pasteur
(1822-1895)
| Louis Pasteur, a chemist, developed pasteurization while researching
the cause of beer and wine spoilage. The process was applied first in wine preservation.
When milk producers adopted the process, pasteurization eliminated a substantial
quantity of foodborne illness. |
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> Pasteurization
The process of destroying microorganisms that could cause disease. This is usually
done by applying heat to a food.
Food Safety Implication: Pasteurization is the heat processing of a
liquid or food to kill pathogenic bacteria to make a food safe to eat. Using pasteurization
to kill pathogenic bacteria has helped reduce the transmission of diseases, such
as typhoid fever, tuberculosis, scarlet fever, polio, and dysentery. (Also see
Typhoid Fever.)
It's important to note that foods can become contaminated even after they have
been pasteurized. For example, all pasteurized foods must be refrigerated. If
temperature is abused (e.g., if milk or eggs are not kept refrigerated), pasteurized
foods can become contaminated. Therefore, it's important to always handle food
properly by following the 4 Cs.
How It Works: Foods are heat-processed to kill pathogenic bacteria.
Foods can also be pasteurized using gamma irradiation. Such treatments do not
make the foods radioactive. The pasteurization process is based on the following
time and temperature relationship.
- High-Temperature-Short-Time Treatment (HTST) - Using higher heat for
less time to kill pathogenic bacteria. For example, milk is pasteurized at 161°
F (72° C) for 15 seconds.
- Low-Temperature-Long-Time Treatment (LTLT) - Using lower heat for
a longer time to kill pathogenic bacteria. For example, milk is pasteurized at
145° F (63° C) for 30 minutes.
Note: The times and temperatures depend on the type of food and the
final result you want to achieve, such as retaining a food's nutrients, color,
texture, and flavor and using a high enough temperature for a long enough time
to kill pathogenic bacteria.
Processes Used to Pasteurize Foods Include:
- Flash Pasteurization - Involves a high temperature, short-time treatment
in which pourable products, such as juices, are heated for 3 to 15 seconds to
a temperature that destroys harmful micro-organisms. After heating, the product
is cooled and packaged. Most drink boxes and pouches use this pasteurization method
as it allows extended unrefrigerated storage while providing a safe product.
- Steam Pasteurization - This technology uses heat to control or reduce
harmful microorganisms in beef. This system passes freshly-slaughtered beef carcasses
that are already inspected, washed, and trimmed, through a chamber that exposes
the beef to pressurized steam for approximately 6 to 8 seconds. The steam raises
the surface temperature of the carcasses to 190° to 200° F (88° to
93° C). The carcasses are then cooled with a cold-water spray. This process
has proven to be successful in reducing pathogenic bacteria, such as E. coli
O157:H7, Salmonella, and Listeria, without the use of any chemicals.
St pasteurization is used on nearly 50% of U.S. beef.
- Irradiation Pasteurization - Foods, such as poultry, red meat, spices,
and fruits and vegetables, are subjected to small amounts of gamma rays. This
process effectively controls vegetative bacteria and parasitic foodborne pathogens
and increases the storage time of foods.
Some Examples of Foods That Are Commonly Pasteurized:
- Whole Eggs Removed from Shells and Sold As a Liquid - Large quantities
of eggs are sold to restaurants and institutions out of the shell. The yolk and
whole-egg products are pasteurized in their raw form. The egg white is pasteurized
in its raw form if it is sold as a liquid or frozen product.
- Dried Eggs - If eggs are sold dried, the egg white with the glucose
removed is normally heat-treated in the container by holding it for 7 days in
a hot room at a minimum temperature of 130° F (54° C).
- Whole Eggs Pasteurized in the Shell - Traditionally, eggs sold to
customers in the shell have not been pasteurized. However, new time/temperature
pasteurization methods are making this possible. Egg whites coagulate at 140°
F (60° C). Therefore, heating an egg above 140° F would cook the egg,
so processors pasteurize the egg in the shell at a low temperature, 130° F
(54° C), for a long time, 45 minutes. This new process is being used by some
manufacturers, but it is not yet widely available.
Note: Pasteurizing eggs reduces the risk of contamination from pathogenic
bacteria, such as Salmonella, which can cause severe illness and even death.
Pasteurized eggs in the shell may be used in recipes calling for raw eggs, such
as Caesar salad, hollandaise or béarnaise sauces, mayonnaise, egg nog,
ice cream, and egg-fortified beverages that are not thoroughly cooked.
- Milk - Pasteurization improves the quality of milk and milk products
and gives them a longer shelf life by destroying undesirable enzymes and spoilage
bacteria. For example, the liquid is heated to 145° F (63° C) for at least
30 minutes or at least 161° F (72° C) for 15 seconds.
Today, many foods, such as eggs,
milk, juices, spices and ice cream,
are pasteurized.
Sometimes higher temperatures are applied for a shorter period of time. The
temperatures and times are determined by what is necessary to destroy pathogenic
bacteria and other more heat-resistant disease-causing microorganisms that may
be found in milk. The liquid is then quickly cooled to 40° F (4° C).
Other liquids, such as juices, are heat-processed in a similar manner. Temperatures
and times vary, depending on the product and the target organism. Other types
of milk pasteurization include:
- Ultrapasteurization - This involves the heating of milk and cream
to at least 280° F (138° C) for at least 2 seconds, but because of less
stringent packaging, they must be refrigerated. The shelf life of milk is extended
60 to 90 days. After opening, spoilage times for ultrapasteurized products are
similar to those of conventionally pasteurized products.
- Ultra-High-Temperature (UHT) Pasteurization - typically involves heating
milk or cream to 280° to 302° F (138° to 150° C) for 1 or 2 seconds.
The milk is then packaged in sterile, hermetically-sealed (airtight) containers
and can be stored without refrigeration for up to 90 days. After opening, spoilage
times for UHT products are similar to those of conventionally pasteurized products.
> Pathogen
Any microorganism that is infectious or toxigenic and causes disease. Pathogens
include parasites, viruses, and some fungi/yeast and bacteria.
Food Safety Implication: If food is not properly handled, pathogens
can contaminate food and cause foodborne illness when the food is eaten. (See
The 12 "Most Unwanted" Bacteria at right.)
> Perishable
Food that is subject to decay, spoilage or growth of pathogenic bacteria unless it is properly refrigerated or frozen.
Food Safety Implication: Perishable foods can spoil quickly and become
unsafe to eat if they are not properly stored.
Food Safety Precautions:
- When shopping, buy perishable foods last and only when you can take them
home right away.
- Always store perishable foods in the refrigerator or freezer to prevent bacterial
growth.
- Avoid leaving perishables out at room temperature for more than 2 hours.
Perishable Foods Include:
- Dairy Products
- Produce
- Meat
- Seafood
- Poultry
> pH
The measure of the acidity (less than 7) or alkalinity (greater than 7) of a solution.
Acidity is measured on a pH scale of 0 to 14, with a neutral pH being 7. The
pH is acidic if it is lower than 7. The more acidic, the lower the number on the
scale.
Most bacteria will not grow at pH levels
below 4.6. Microorganisms thrive in a pH range above 4.6.
Food Safety Implication: Most bacteria will not grow in acidic foods
with a pH level below 4.6. Microorganisms thrive in a pH range above 4.6. That's
why acidic foods, such as vinegar and citrus fruits, are not favorable foods for
pathogenic bacteria to grow in. However, bacteria may survive in the food.
Some examples of high-acid foods include: all fruits, except figs, most tomatoes,
pickles, sauerkraut, jams, jellies, marmalades, fruit butters, and fermented and
pickled (treated with brine or vinegar solution to inhibit the growth of microorganisms)
vegetables.
> Phage Typing
A classification procedure that uses bacteriophages (viruses that infect bacteria)
to distinguish between bacterial isolates that belong to the same genus and species.
Each bacterial strain will exhibit resistance to some phages and be susceptible
to infection by others. A battery of standard phages is used to test bacterial
isolates. The profile of resistance and susceptibility is called the phage type.
Food Safety Implication: Phage typing helps food scientists determine
if bacterial isolates obtained from groups of ill people are different or indistinguishable
from each other.
> Plasmid Transfer with E. coli
Plasmids carry a number of genetic elements, which can be transferred between
and among related bacteria. For example, E. coli cells can naturally transfer
some plasmids from cell to cell by the process of conjugation.
Food Safety Implication: Plasmid transfer may cause new foodborne pathogens
to emerge, and sometimes genetic elements that plasmids transfer from one bacterium
to another can make the receiving bacterium pathogenic or resistant to antibiotics.
Plasmid Transfer
> Point of Service (POS)
The establishment where an implicated food is consumed or sold to the consumer.
An establishment can include restaurants, grocery stores, caterers, banquets,
or a private residence.
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| In prehistoric times, people preserved food by drying it in the sun
or storing it in cool caves. Today, science has developed other methods of preservation,
such as canning, freeze-drying, and irradiation. |
Salt is a good food preservative.
Salt is considered antibacterial because it restricts bacterial growth in
many foods. It preserves foods by lowering the amount of "free" water molecules
in foods. Bacteria need moisture in order to thrive, so without enough "free"
water, they cannot grow well in foods that contain salt.
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> Preservation
A variety of methods used at the processing stage and at home to keep food safe
from harmful bacteria and extend the storage life of food. (Also see Canning
and Freezing.)
Food Safety Implication: Foods are preserved so that they can be safely
eaten at a later time. Some preservation methods include: canning, drying, freezing,
smoking, and pickling (treating foods with brine or vinegar solution to inhibit
the growth of microorganisms).
Food Safety Precaution: Read and follow all instructions on food labels
for storage, handling, and cooking of foods.
> Pulse-Field Gel Electrophoresis (PFGE)
The DNA "fingerprinting" method that scientists use to determine the source of
bacteria in foods.
Pulse-Field Gel Electrophoresis
Food Safety Implication: Bacterial DNA "fingerprints" are generated
by pulse-field gel electrophoresis (PFGE), which can distinguish between different
strains of a bacterium, such as E. coli. Similar PFGE patterns suggest
that 2 different E. coli isolates - such as one from a patient and one
from food - come from a common source, and identifying these connections can help
determine the cause of an outbreak. Finding similar patterns can also help scientists
determine whether an outbreak is occurring, even if the affected persons are geographically
far apart.
How It Works: The DNA is first digested into pieces by reacting the
isolated DNA with enzymes that are able to specifically break the DNA molecule
into individual pieces. The digested DNA is placed at one end of the gel. A pulsing
electric field applied across the gel drives the DNA pieces into the gel over
a period of hours. The smallest pieces slip through the pores of the gel more
quickly, so the pieces are separated as distinct bands in the gel, based on size.
The resulting pattern of 30 to 50 bands, which resembles a bar code is the "fingerprint."
A DNA "Fingerprint"
> PulseNet
A national network of public health laboratories that performs DNA "fingerprinting"
on foodborne bacteria. The network permits rapid comparison of these "fingerprint"
patterns through an electronic database at the Centers for Disease Control and
Prevention (CDC). This network was set up in 1995.
PulseNet Logo
Food Safety Implication: Today, the use of PulseNet helps to better
detect the source of foodborne bacteria in foods, which cause foodborne illness.
Any one of the laboratories (approximately 70 laboratories at this publication)
in CDC's PulseNet network can fingerprint E. coli in less than 24 hours,
whereas the process used to take days or weeks.
Using DNA "fingerprint" technology, PulseNet helps public health authorities
recognize when cases of foodborne illness are occurring at the same time in geographically
separate locales. These illnesses may be caused by the same strain of bacteria
and may be due to a common exposure, such as a common food that was eaten. An
epidemiologic investigation of those cases can then determine what they have in
common. Control measures can be initiated and outbreaks stopped.
How It Works: Laboratories participating in PulseNet perform DNA "fingerprinting"
by pulse-field gel electrophoresis (PFGE) on disease-causing bacteria isolated
from humans and from suspected food using standardized equipment and methods.
Once PFGE patterns are generated, they are entered into an electronic database
of DNA "fingerprints" at the state or local health department and transmitted
to the CDC where they are filed in a central computer.
When PulseNet is fully operational, all participating laboratories will have
a direct link with the central computer at CDC. These laboratories will be able
to submit new patterns to the national database online and obtain epidemiologic
information associated with patterns in the database. If patterns submitted by
laboratories in different locations during a defined time period are found to
match, the CDC computer will alert PulseNet participants of a possible multi-state
outbreak, so that a timely investigation can be done.
Foodborne Illness-Causing Bacteria Currently Being Tracked by PulseNet:
Currently, PulseNet participants perform DNA "fingerprinting" by PFGE on E.
coli O157:H7 isolates. In February 1998, CDC introduced a standardized method
for PFGE analysis of Salmonella serotype Typhimurium that uses the same
equipment. Over time, additional foodborne illness-causing bacteria will be tracked
by PulseNet depending on their public health importance and the availability of
specific DNA "fingerprinting" methods for that pathogen.
The Step-by-Step Process for Tracing a Food Implicated in a Foodborne Illness
Outbreak:
Is PulseNet the only national network that tracks pathogens?
No. Currently, PulseNet tracks only Salmonella, E. coli O157:H7 (and other Shiga-toxin producing E. coli), Listeria monocytogenes, Shigella, Campylobacter jejuni, and Vibrio cholerae. The Public Health Laboratory Information
System (PHLIS), a national network of public health laboratories, tracks all organisms.
PulseNet is a part of PHLIS. Both networks help to better detect a foodborne outbreak
in multiple states.
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- A person experiencing the symptoms associated with foodborne illness (diarrhea,
abdominal cramps, nausea, fever, vomiting, or body aches) goes to the doctor.
The doctor makes an initial diagnosis and stool cultures from the patient are
sent to a clinical laboratory.
- Medical lab tests are done on the stool culture. If the presence of foodborne
bacteria is determined by the local clinical lab, an isolate of that bacterial
culture is sent to the state health department lab for further testing, including
PFGE (pulse-field gel electrophoresis). The state health department lab sends
the PFGE results electronically to the Centers for Disease Control and Prevention
(CDC).
The DNA "fingerprint" (PFGE result) is compared at CDC with other "fingerprint"
samples from the other states that do PFGE testing (approximately 70 laboratories in 51 states and territories at this publication). If there are other states reporting this same pattern, CDC
notifies - via an automated e-mail - the state health departments, along with
the Food and Drug Administration (FDA) and the U.S. Department of Agriculture
(USDA), the 2 agencies that are responsible for the safety of food that travels
interstate.
In other instances, local and state health departments identify an outbreak
or cluster of sporadic cases and the suspected food source without PFGE testing.
When other similar outbreaks or clusters of sporadic cases are identified in a
particular state or other states, PFGE testing is then used to link them along
with the fact that a common food is involved.
- When there are several isolates with the same PFGE pattern, state health
departments investigate to identify a common exposure, such as a common food that
was eaten. Local health department representatives use standard questionnaires
to interview both sick and well persons. First, they want to find out whether
the foodborne illness was due to a point of service (POS) mistake. The point of
service could be such places as your table at home, a picnic, or a restaurant.
Health department representatives look for common answers - for example, a common
meal that was eaten by all or a common event that was attended.
- If it is determined that the foodborne illness was due to food that was served
at a banquet or restaurant, for example, local health department representatives
will interview the food workers. They use standard questionnaires to find out
what and how foods were prepared. In some cases, if there was a sick food worker
on the job on the day in question, stool cultures from the food worker may be
requested to determine if he or she was sick from the same organism and if his
or her PFGE matches the persons who became sick. If the worker was the source
of the contamination, a food source investigation would not be needed.
- Once the common food is identified and the food source is suspected, CDC notifies
FDA or USDA (the agency that is notified depends on which agency has jurisdiction
over the food), who in turn uses trace-back techniques to determine the source
of the food.
- Once the traceback investigation has determined the source of the outbreak,
steps are taken to prevent further exposure or spread of the infection. For example,
if the source is a specific food being distributed, a recall of that food will
be implemented. If the source is an infected food worker, that person will be
removed from any food-service duties until they have recovered and tested negative
for that bacteria.
> Pure Food and Drug Act
The passage of this act in 1906 allowed the government to gain control over the
economic adulteration (impurities) of food and use of chemicals. This act set
up mechanisms for protecting the food supply. The Food and Drug Administration
enforces this act.
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