When raw meat or poultry is dehydrated
at home either in a warm
oven or a food dehydrator to make jerky which will be stored on the shelf,
pathogenic bacteria are likely to survive the dry heat of a warm oven and especially the
130 to 140 F of a food dehydrator. Included here is the scientific background behind
drying food to make it safe and the safest procedure to follow when making homemade jerky.
What is Jerky? |
This product is a
nutrient-dense meat that has been made lightweight by drying. A pound of meat or
poultry weighs about four ounces after being made into jerky. Because most of the
moisture is removed, it is shelf stable can be stored without refrigeration
making it a handy food for backpackers and others who dont have access to
refrigerators.
Jerky is a food known at least since ancient Egypt. Humans made
jerky from animal meat that was too big to eat all at once, such as bear, buffalo, or
whales. North American Indians mixed ground dried meat with dried fruit or suet to
make "pemmican." "Biltong" is dried meat or game used in many African
countries. Our word "jerky" came from the Spanish word
"charque." | | | |
How Can Drying Meat Make it
Safe? |
Drying is the worlds
oldest and most common method of food preservation. Canning technology is less than
200 years old and freezing became practical only during this century when electricity
became more and more available to people. Drying technology is both simple and
readily available to most of the worlds culture.
The scientific principal of preserving food by drying is that by
removing moisture, enzymes cannot efficiently contact or react with the food. Whether
these enzymes are bacterial, fungal, or naturally occurring autolytic enzymes from the raw
food, preventing this enzymatic action preserves the food from biological action. |
What are the Types of Food
Drying? |
There are several types of
food drying. Two types of natural drying sun drying and "adibatic"
(shade) drying occur in open air. Adibatic drying occurs without heat. Solar
drying sometimes takes place in a special container that catches and captures the
suns heat. These types of drying are used mainly for fruits such as apricots,
tomatoes, and grapes (to make raisins).
Drying from an artificial heat source is done by placing food in either
a warm oven or a food dehydrator. The main components of an electric food
dehydrator include:
- a source of heat;
- air flow to circulate the dry air;
- trays to hold the food during the drying process; and
- mesh or leather sheets to dry certain types of foods.
|
Why is Temperature Important
When Making Jerky? |
Illnesses due to
Salmonella and E. coli O157:H7 from homemade jerky raise questions about the
safety of traditional drying methods for making beef and venison jerky. The USDA
Meat and Poultry Hotlines current recommendation for making jerky safely is to
heat meat to 160 F before the dehydrating process. This step assures that any
bacteria present will be destroyed by wet heat. But most dehydrator instructions do
not include this step, and a dehydrator may not reach temperatures high enough to heat
meat to 160 F.
After heating to 160 F, maintaining a constant dehydrator temperature
of 130 to 140 F during the drying process is important because:
- the process must be fast enough to dry food before it spoils; and
- it must remove enough water that microorganisms are unable to grow.
|
Why is it a Food Safety
Concern to Dry Meat Without First Heating it to 160 F? |
The danger in dehydrating
meat and poultry without cooking it to a safe temperature first is that the appliance will
not heat the meat to 160 F a temperature at which bacteria are destroyed
before it dries. After drying, bacteria become much more heat resistant.
Within a dehydrator or low-temperature oven, evaporating moisture
absorbs most of the heat. Thus, the meat itself does not begin to rise in
temperature until most of the moisture has evaporated. Therefore, when the dried
meat temperature finally begins to rise, the bacteria have become more heat resistant and
are more likely to survive. If these surviving bacteria are pathogenic, they can
cause foodborne illness to those consuming the jerky. |
What Research Findings Exist
on the Safety of Jerky? |
There have been several
scientific studies of meat dehydrating and lab tests on jerky samples by the following
professionals: Judy Harrison, Cooperative Extension Service, University of Georgia;
Mark Harrison, the Center for Food Safety and Quality Enhancement, Department of
Food Science and Technology, University of Georgia; Richard A. Holley, Food Research
Institute, Agriculture Canada, in Ontario; and William Keene of the Oregon Health Division.
In studies, the meat dehydrated included slices of beef from the round, loin, or
flank; corned beef slices; and ground beef formed in jerky presses. Keene examined
homemade venison jerky which infected 11 people with E. coli O157:H7.
In a related work, factors affecting the heat resistance of E. coli
O157:H7 was the subject of an April 1998 piece by J. Kauer et al., Letters of Applied
Bacteriology, Vol. 26, No. 4, page 325.
In the jerky studies, some samples showed total bacterial destruction
and other samples showed some bacterial survival especially the jerky made with
ground beef. Further experiments with lab-inoculated venison showed that pathogenic
E. coli could survive drying times of up to 10 hours and temperatures of up to 145
F.
A recent study by the Harrisons and Ruth Ann Rose, also with the
University of Georgia, was published in the January 1998 Journal of Food Protection,
Vol. 61, No. 1. The authors analyzed ground beef jerky made with a commercial beef
jerky spice mixture with and without a curing mix containing salt and sodium nitrite.
Half of the ground beef was inoculated with E. coli O157:H7
before making it into jerky strips and dehydrating it. The authors found that in
both the heated and unheated samples, the jerky made with the curing mix had greater
destruction of bacteria than jerky made without it. The jerky made with the mix and
heated before dehydrating had the highest destruction rate of bacteria.
They concluded, "For ground beef jerky prepared at home, safety concerns related
to E. coli O157:H7 are minimized if the meat is precooked to 160 F prior to
drying." |
What are the USDA Meat and
Poultry Hotlines Recommendations for Making Homemade Jerky? |
Research findings support
what the Hotline has been recommending to callers. Additionally, safe handling and
preparation methods must always be used, including:
Always wash hands thoroughly with soap and water before and after
working with meat products.
Use clean equipment and utensils.
Keep meat and poultry refrigerated at 40 F or slightly below; use
or freeze ground beef and poultry within 2 days; whole red meats, within 3 to 5 days.
Defrost frozen meat in the refrigerator, not on the kitchen counter.
Marinate meat in the refrigerator. Dont save marinade to
re-use. Marinades are used to tenderize and flavor the jerky before dehydrating it.
Steam or roast meat and poultry to 160 F as measured with a meat
thermometer before dehydrating it.
Dry meats in a food dehydrator that has an adjustable temperature
dial and will maintain a temperature of at least 130 to 140 F throughout the drying
process.
|
Are There Special
Considerations for Wild Game Jerky? |
Yes, there are other special
considerations when making homemade jerky from venison or other wild game. According
to Keene and his co-authors, "Venison can be heavily contaminated with fecal bacteria
the degree varying with the hunters skill, wound location, and other factors.
While fresh beef is usually rapidly chilled, deer carcasses are typically held at
ambient temperatures, potentially allowing bacteria multiplication." |
Jerky
Products |
Buffalo Bills 1.75oz Beef Jerky 6-Pack Gift Cooler (filled with 11 assorted 1.75oz packs of Buffalo Bills beef jerky)
Bavaria Landjager
Just Jerky: The Complete Guide to Making It
|
Is Commercially Made Jerky
Safe? |
Yes, the process is monitored
in federally inspected plants by inspectors of the U.S. Department of Agricultures
Food Safety and Inspection Service. Products may be cured or uncured, dried, and
may be smoked or unsmoked, air or oven dried. The following terms may be on
processed jerky products:
"Beef Jerky" produced from a single piece of
beef.
"Beef Jerky Chunked and Formed" produced from
chunks of meat that are molded and formed, then cut into strips.
"Beef Jerky Ground and Formed or Chopped and Formed"
produced from ground or chopped meat, molded and cut into strips. Beef Jerky
containing binders or extenders must show true product name (e.g., "Beef and Soy
Protein Concentrate Jerky, Ground and Formed").
"Species (or Kind) Jerky Sausage" the product
has been chopped and may be dried at any stage of the process, and it is stuffed into
casings.
|
What is the Safe Storage Time
for Jerky? |
Commercially packaged jerky can be kept 12
months; home-dried jerky can be stored 1 to 2 months. |
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