This information has been reviewed and adapted for use in South Carolina by P.H. Schmutz, HGIC Food Safety Specialist; W. Scott Whiteside, Extension Associate, Packaging Science; and E.H. Hoyle, Extension Food Safety Specialist, Clemson University. (New 11/01. Revised 06/07.)
Vacuum-packaging machines or vacuum sealers are available to vacuum package foods at home. This process may extend the storage time of refrigerated foods, dried foods and frozen foods, but it may increase the danger of growing disease-causing bacteria as well. Vacuum packaging is not a substitute for safely processing perishable foods to be stored at room temperature. Perishable foods that are vacuum packaged must still be kept refrigerated or frozen at proper temperatures.
Vacuum packaging involves removing air from the food package. Oxygen in the air promotes certain reactions in foods that can cause the foods to deteriorate. Therefore, the removal of oxygen from the food package does extend the storage quality of preserved foods. For example, the presence of oxygen can cause fats to become rancid or foods to change colors. (For this reason, materials such as plastic wrap or freezer paper that block out oxygen as well as moisture are recommended for wrapping foods for storage.)
The removal of oxygen from a food package does not eliminate the possibility for all bacterial growth. Although it is likely to eliminate spoilage bacteria that cause deterioration in the quality of food in ways that would let you know the food was going bad (odor, color, sliminess, etc.), some pathogenic (disease-causing) bacteria prefer low-oxygen environments and reproduce well in vacuum-packaged foods.
For example, C. botulinum bacteria that cause the deadly botulism poisoning grow at room temperature in low-acid, moist foods in a low-oxygen environment. If spoilage bacteria are not present, C. botulinum bacteria can reproduce even easier, making the food unsafe without obvious symptoms of the food being spoiled to warn the consumer. Oxygen in the environment offers some protection against C. botulinum growth in foods that are not vacuum packaged.
Vacuum packaging of dry, non-perishable foods such as nuts and crackers does extend their storage quality and these products are low enough in moisture that bacterial growth is prevented. However, these foods also store well in airtight containers without the expense of a vacuum-packaging machine.
It is important to remember that perishable foods that are vacuum-packaged must still be stored in the refrigerator or freezer. Although the quality of the food may be extended, it is still possible that disease-producing bacteria may be present.
Perishable foods must be kept either in the refrigerator between 34 and 40 °F, or for longer storage, in the freezer at 0 °F or below.
Vacuum-packaged foods that are stored frozen will be safe, but precautions must be taken when these foods are thawed. 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. That is why it is important that these foods be thawed at proper refrigerator temperatures and not on the kitchen counter at room temperatures. Never leave thawed, vacuum-packaged foods at room temperature.
Whether storing foods that have been vacuum-packaged in the home, or those packaged with conventional materials, it is important to follow basic safe food handling practices. Remember, removing oxygen from a food's environment does not just solve some food storage problems; it could cause others. It is important that safe handling practices 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 more information on the proper handling of foods, request HGIC 3500, Basics of Safe Food Handling.
Andress, Elizabeth L. (1999). Should I Vacuum Package Food at Home? http://www.uga.edu/nchfp/publications/uga/vacuum_packaging.html
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