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Should I Vacuum Package
Food at Home?
There are numerous types of equipment being
marketed for vacuum packaging food at home. They vary greatly in
technological sophistication and price, and usually are called vacuum
packaging machines or vacuum sealers. These machines may extend the
storage time of refrigerated foods, dried foods and frozen foods.
However, vacuum packaging is not a substitution for the heat processing
of home canned foods.
Neither is vacuum packaging a substitution for refrigerating or freezing
foods that would otherwise require it. In fact, vacuum packaging can add
to the concerns associated with storing of these perishable foods (foods
not stable at room temperature and requiring cold storage).
There are many precautions that must be taken when vacuum packaging
perishable foods for refrigerator or freezer storage. You must assume
that the perishable food carries the risk of potential pathogenic
contamination. And, when frozen food is ready to be thawed and used,
steps to minimize the risks from microorganisms in food must still be
followed. Again, perishable foods must still be refrigerated or frozen
for storage after packing in a vacuum or partial vacuum environment.
Producing a vacuum means removing air from the contents of a package.
Oxygen in environmental air does promote certain reactions in foods,
causing quality deterioriation. For example, oxidative rancidity of fats
in food and certain color changes are promoted by the presence of
oxygen. Therefore, removal of oxygen will preserve certain quality
characteristics and extend the food’s shelf life based on quality.
However, removal of oxygen from the surrounding environment does not
eliminate the possibility for all bacterial growth; it just changes the
nature of what is likely to occur. In fact, what is most likely to
be eliminated is growth of spoilage bacteria. The bacteria that normally
spoil food in noticeable ways (odor, color, sliminess, etc.) like to
have oxygen in the environment. If able to multiply on foods, these
spoilage bacteria let us know if a food is going bad before it reaches
the point it makes someone sick. In the almost oxygen-free environment
of a vacuum packaging, the spoilage bacteria do not multiply very fast
so the loss of food quality is slowed down.
Some pathogenic (illness-causing) bacteria, however, like low-oxygen
environments and reproduce well in vacuum-packaged foods. In fact,
without competition from spoilage bacteria, some pathogens reproduce
even more rapidly than in their presence. These bacteria often do not
produce noticeable changes in the food, either. In the vacuum-packaged
environment, food may become unsafe from pathogenic bacterial growth
with no indicators to warn the consumer because the spoilage bacteria
that would normally be making food unappealing are not multiplying.
For example, C. botulinum (a very dangerous pathogen that causes the
deadly botulism poisoning under certain conditions) grows at room
temperature in low-acid moist foods if a package lacks oxygen —if the
bacteria are present, of course. Without competition from spoilage
bacteria, reproduction is even easier. Proper refrigeration at 38-40o F
becomes a critical step for storage of low-acid vacuum-packaged foods
that don’t keep at room temperature.
The removal or reduction of oxygen in the storage
environment is indeed helpful for extending the storage quality of
non-perishable dry foods such as dried nuts or crackers. Products like
this are low enough in moisture that bacterial growth is prevented.
Vacuum packaging can also be safe for food that will be stored frozen.
However, proper thawing under conditions that minimize bacterial growth
— like refrigeration — would be essential. If the package stays closed
during thawing, you still have a vacuum environment where pathogenic
bacteria can be active if the temperature is warm enough.
There is no advantage to combining the use of a vacuum packaging machine
with boiling water or pressure canning of foods. Jars processed in
either canner develop sufficient vacuums for safe, stable storage at
room temperature. They also have the added advantage of a heat process
that kills pathogenic bacteria able to grow in that food at room
temperature.
So is a vacuum packaging machine needed or are there advantages to
owning one? One would need to ask if the amount of the investment is
worth the uses for the appliance. Traditionally recommended freezing
procedures and packaging methods, if carried out carefully, will produce
high quality products with reasonably lengthy storage times. Storing
crackers, nuts and other dried foods in air-tight storage containers
will also keep them of high quality for a reasonable period of time for
normal usage.
And, perishable foods still need to be treated carefully to prevent
pathogens from making them unsafe. Remember, removing oxygen from a
food’s environment does not just solve some food storage problems— it
could cause others. Consider how carefully safe food handling practices
will be followed at all times, since vacuum packaging creates very good
conditions for some pathogens to be a problem if any mistakes are made.
For example, perishable food being vacuum packaged should not be out of
refrigeration very long—no longer than 2 hours total time above 40°F.
Food that needs to be refrigerated without vacuum packaging still needs
to be refrigerated! While food is being packaged and prepared or used
later, extremely clean hands, and clean and sanitized equipment and work
surfaces are essential. Food should be dated and still used within
reasonable storage times unless frozen. Raw meats, poultry and seafood
should be cooked thoroughly to recommended temperatures, measured with a
food thermometer, before eating. Any food showing signs of spoilage
should be discarded – when in doubt, throw it out!
Adapted from the University of Georgia. Andress, E.
(1999). Should I Vacuum Package Food at Home?
Elizabeth L. Andress, Ph.D. Associate Professor and Extension Food
Safety Specialist, National Center for Home Food Preservation
Other April 2006 Articles:
Plan Ahead for Home Canning this Summer
Mushroom
Seekers Hope April Rains Brings Morels
Buying a
Pressure Canner?
Cynthia
Fauser
fauserc@missouri.edu
Nutrition Specialist
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April
2006
