Individually wrapped pieces of frozen fish are a fantastic, healthy option, to buy at your local grocery store because they are easy to store and prepare. The vacuum packaging -- also known as Reduced Oxygen Packaging (ROP) -- extends shelf life because it reduces odors and texture changes that cause fish to spoil. It also prevents water loss and keeps the fish from drying out. But, if you do choose to purchase fish that is packaged this way, it's incredibly important to handle it properly because there is a hidden health risk.
When you thaw frozen fish, there is a high risk of botulism because of the Clostridium botulinum and Listeria monocytogenes, the bacteria in vacuum packed fish. Botulism is a life-threatening disease that attacks the nervous system, and some of the symptoms include weakening muscles around the eyes, mouth, and throat, and it can also spread to other muscles in the arms and legs. In the most severe cases, it can result in difficulty breathing and sometimes death. Knowing how to thaw your fish correctly can be a lifesaver.
Clostridium Botulinum (C. botulinum) is an anaerobic bacteria, which means that it forms spores that live and grow in low oxygen conditions. That is the exact environment that vacuum-sealed packages create, and with the right conditions, the spore can develop into a vegetative cell and produce a deadly toxin.
To prevent this from happening, Michigan State University Extension says keeping your frozen fish at the proper temperature is critical. The higher the temperature, the faster the C. botulinum forms toxin. If your freezer or refrigerator (wherever you store your frozen fish) is above 38 degrees Fahrenheit, the time it takes to form toxin is significantly shortened, greatly increasing the risk of botulism.
And, if you thaw your fish in cold water, it can also be above the 38-degree mark.
Listeria Monocytogenes is a bacterium that can contaminate your food, and unlike many bacteria, it can grow and multiply on foods in your refrigerator. If it is in your food, it can cause serious illness to pregnant women, older adults, and those with weakened immune systems.
When you buy individually wrapped frozen fish, the first thing to do is to read the packaging. It will most likely tell you to keep it frozen until you use it. And, when you are ready to thaw the fish (either in the refrigerator or in water) first remove it from the vacuum-sealed packaging.
When you open the packaging for thawing, it exposes the fish to oxygen which will stop the spores and not allow them to produce the vegetative cells that produce toxin.
The Food and Drug Administration says that the safest way to thaw frozen fish is to put in the refrigerator overnight. But, no matter which method you choose, always remove the packaging first.
Individually wrapped vacuum-sealed fish can be part of a tasty meal that is low in calories and full of protein. But, before you cook it, make sure to follow the thawing recommendations to avoid the health risk.
And remember, temperature is key. Store your frozen fish in a freezer below 38 degrees, and when it is time to thaw, remove it from the packaging immediately. Because once packaged fish gets warmer than 38 degrees, the consequences of eating it could be fatal.