MSU Extension Safe Food & Water

Looking for vacuum-packed fish is an excellent way to purchase fish in the grocery store. Vacuum packaging keeps the fish from drying out by preventing water loss; it also can ensure the fish is packaged at peak quality.

Vacuum packaging, also called reduced oxygen packaging (ROP), limits oxygen and allows for extended shelf life in the freezer by reducing odors and texture changes that may result in spoilage. When food is vacuum packed, air is sucked out of the packaging, and then that packaging is hermetically sealed. It is important to handle the fish correctly, as there is a risk for bacterial growth that can lead to a foodborne illness if the product is handled incorrectly.

What is the concern? Clostridium botulinum and Listeria monocytogenes are the bacteria of primary concern when thawing vacuum-packed fish.

Clostridium botulinum (C. botulinum) is an anaerobic bacteria (meaning they live and grow in low oxygen conditions) that forms spores which allow it to survive in unfavorable conditions. When the right conditions are present, the spore will develop into a vegetative cell, which can produce a deadly toxin. This toxin can cause a life-threatening disease called botulism.

In order to prevent the production of toxins, Michigan State University Extension advises keeping food, such as fish that is vacuum packaged, at the proper temperature and/or thawing the product correctly. C. botulinum forms the toxin more rapidly at higher temperatures than at lower temperatures, so the recommended storage temperature from the FDA is 38 degrees Fahrenheit or lower in the refrigerator or keep frozen below zero degrees. As storage increases above 38 degrees Fahrenheit, the time required for toxin formation is significantly shortened. Check to ensure your home refrigerator can maintain temperatures below 38 degrees Fahrenheit. Additionally, if thawing the fish in cold water, the temperature may also be above 38 degrees Fahrenheit, so the time thawing would need to be monitored.

All ROP fish must be labeled, “KEEP FROZEN UNTIL TIME OF USE.” Opening the packaging while thawing the vacuum packaged fish, introduces oxygen and the spores will not produce the vegetative cells that produce the toxin.

Listeria monocytogenes is a bacterium that can contaminate food. If present, it can cause a serious illness primarily for high-risk groups, such as older adults, pregnant women, children under five, and adults with weakened immune systems. Listeria can grow and multiply in some foods in the refrigerator. Vacuum-packed fish is not commercially stable or shelf-stable, so must be refrigerated or kept frozen. When thawing, it is very important to follow thawing guidelines provided by the processor that will be located on the packaging of the fish.

Vacuum-packaged fish results in a safe and delicious product when it is prepared, as vacuum sealing food keeps its color, texture and flavor longer by being preserved at peak quality. It is important to follow the thawing recommendations when preparing the product at home to keep your family safe from foodborne illness.

For more information on food safety, visit MSU Extension's Safe Food & Water website.