Proper handling needed for vacuum sealed foods

There are a number of systems marketed for vacuum packing foods at home. Vacuum sealing may extend the storage time of refrigerated foods, dried foods and frozen foods, said Barbara Brown, Oklahoma State University Cooperative Extension Service food specialist.

“While vacuum sealing has the ability to extend the shelf life and quality of food, it’s not a substitution for the heat processing of home canned foods, nor is it a substitution for refrigerator or freezer storage of foods that would otherwise require it,” Brown said. “Consumers must keep in mind that perishable foods must still be refrigerated or frozen for storage after packing in a vacuum or partial vacuum environment.”

 When considering vacuum packaging, consumers must assume that the perishable food carries the risk of potential pathogenic contamination. When frozen foods that have been vacuum sealed are ready to be thawed, steps to minimize risks from microorganisms in food must be followed.

Brown said that producing a vacuum means removing air from the contents of the package. Oxygen in the environmental air promotes certain reactions in foods which cause deterioration of quality.

“Oxidative rancidity of fats in food is promoted by oxygen. Removing the oxygen can help preserve certain quality characteristics and extend the food’s shelf life based on quality,” she said.

 It is important for consumers to keep in mind that removal of oxygen from the environment does not eliminate the possibility for all bacterial growth. What is most likely to be eliminated is the growth of spoilage bacteria. This is the type of bacteria that normally spoils the quality of food in noticeable ways such as an off-color, odor or sliminess. When these bacteria are able to multiply on food they are able to let a consumer know the food is bad before it reaches the point of making a person sick.

“In a nearly oxygen-free environment like vacuum packaging creates, the spoilage bacteria don’t multiply very fast so the loss of food quality is slowed down,” Brown said. “However, some illness-causing bacteria actually like the low-oxygen environments and reproduce well in vacuum-packaged foods. Without competition from spoilage bacteria, some pathogens are able to reproduce even more rapidly. Unfortunately, these bacteria often don’t produce noticeable changes in the food.”

Food may become unsafe from pathogenic bacterial growth with no indicators such as odor or off-color to warn the consumer. Refrigeration at 38 to 40 degrees Fahrenheit is a critical step for storage of low-acid, vacuum-packaged foods that are not otherwise shelf stable.

Brown said vacuum packaging can also be safe for foods that are stored frozen. Keep in mind, though, that proper thawing under conditions that minimize bacterial growth would be essential. She also noted that 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.

“These methods also have the added advantage of a heat process that kills pathogenic bacteria that are able to grow in food at room temperature,” she said.

It is important to always keep food safety in mind. Perishable foods still need to be treated carefully in order to prevent pathogens from making them unsafe. Removing the oxygen from a food’s environment does not solve some food storage problems – it can actually cause other problems.

“Consider how carefully safe food handling practices will be followed at all times since vacuum packaging creates good conditions for some pathogens to be a problem if any mistakes are made,” Brown said. “Always make sure all surfaces, utensils and your hands are clean when packaging foods for storage. Follow safe thawing methods and use a food thermometer when cooking. If you see any signs of spoilage the food should be discarded.”

###

Oklahoma State University, U.S. Department of Agriculture, State and Local Governments Cooperating: The Oklahoma Cooperative Extension Service offers its programs to all eligible persons regardless of race, color, national origin, religion, gender, age, disability, or status as a veteran, and is an equal opportunity employer.
 
Trisha Gedon
Communications Specialist
Agricultural Communications Services
136 Agriculture North
Oklahoma State University
Stillwater, OK  74078
405-744-3625 (phone)
405-744-5739 (fax)
trisha.gedon@okstate.edu