Storage time of dried foods, frozen foods and refrigerated foods may be extended by use of these machines. However, vacuum packaging itself can lead to a false sense of security about the safety of food. The following information is in response to questions asked regarding home vacuum packaging of foods and assumptions that are made about this type of equipment.
According to the National Center for Home Food Preservation, it is important to understand that vacuum packaging is not a substitute for heat processing of home-canned foods. Vacuum packaging also is not a substitute for freezing or refrigeration of perishable foods. Vacuum packaging, in fact, can add to concerns associated with these foods.
Removal of oxygen from a food’s environment does not just solve some food storage problems, it can cause others. Perishable foods are subject to the risk of contamination by pathogenic (disease-causing) bacteria. Perishable food must be refrigerated or frozen after it has been packaged in a partial vacuum environment or vacuum-sealed.
The process of vacuum packaging removes air (oxygen) from the contents of a package. One of the most obvious changes we see with vacuum-sealed food is the lack of spoilage from organisms such as mold, bad odor, color change and sliminess within the food product. These types of spoilage serve to give us an indication that the food has become compromised and call into question the safety of the food.
Although removal of oxygen from environmental air can preserve certain quality characteristics and extend the food’s shelf life, removal of oxygen within the package environment does not eliminate the possibility of all bacterial growth.
Of particular concern are the bacteria that grow without air or with limited air supply. These bacteria do not produce noticeable changes in food and can multiply very rapidly without air and the presence of spoilage bacteria, causing food to become unsafe. Without spoilage bacteria present, bacteria (anaerobic) that grow without air can reproduce even at a faster rate.
Clostridium botulinum (if present) is a dangerous pathogen that grows at room temperature in low-acid moist foods (vegetables, meats) in an anaerobic environment (without air). Clostridium botulinum forms spores that can contaminate almost any food. It does not grow well in highly acidic food (tomatoes, citrus fruits, etc.) or food with low moisture (crackers, nuts).
C. botulinum can produce a deadly toxin (poison) when food is time temperature abused. Refrigeration (38 to 40 degrees) is essential for storage of vacuum-packed, low-acid foods that do not keep at room temperature. Both the temperature of the refrigerator and the temperature at which the food is kept are essential to food safety of the food product.
Vacuum packaging can be safe for food that is stored frozen. When frozen food is thawed, it is best to thaw in the refrigerator to slow microorganism growth. Perishable food being vacuumed-packed should not be out of refrigeration longer than 2 hours total time above 40 degrees for safety.