Risky or Not? Thawing Frozen Vacuum-Packed Fish

— Written By and last updated by Meghan Lassiter
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This pandemic has made many of us look differently at technology and ways of learning. One new podcast I enjoy is called Risky or Not? This podcast is available for free to anyone who wants to listen and learn.

The podcast is produced by two Extension Food Safety Specialists, our own Dr. Ben Chapman from N.C. Cooperative Extension and Dr. Don Schaffner, a specialist from Rutgers in New Jersey.

This podcast is short with each edition about 10 minutes. In each podcast Drs. Chapman and Schaffner address one food safety topic, usually, a question that has been asked by a listener or an Extension colleague. Usually, the question is related to food, cooking, or food preservation. They look at research and science and give their rationale for deciding if it is risky or not.

One of their recent programs (#34) was about thawing frozen vacuum-packed fish in the package in the refrigerator. Both agreed that this was a potentially risky situation. I had some in my freezer and dug it out to look at the packaging and yes, there was a warning written on each fillet package that said “do NOT thaw directly in the package.”

Why? There is a potential for botulism growth. 

The professors explained that botulism can grow in an anaerobic (airless) environment. When the fish is vacuum packed, they are creating an anaerobic environment. There is a specific type of botulism that is related to fish and will grow under refrigeration. Botulism is a potentially dangerous and deadly food-borne illness. 

Botulism needs the right temperature and time to grow within the food. If you thaw that the fish in the package in the refrigerator, the conditions may be right for this botulism to grow. The risky temperature for raw fish in a vacuum package is above 38°F. Dr. Chapman looked at research that shows that most home refrigerators are not that low. This research showed that the average home refrigerator is about 45°F. (Hint: it should be below 40°F.) He also expressed concern that most people don’t know the temperature of their refrigerator. Only about 11% of homes have a thermometer in their fridge. Do you?

The temperature of refrigerators can also vary by the time of day, how much food is in the refrigerator, and how many times the door has been opened. You can’t really be sure if the temperature stays below 38°F to safely thaw the fish in the package.

The solution? Easy. Either take the fish out of the package or simply cut a hole in the vacuum package to allow air inside. This is no longer an anaerobic environment. So no longer risky.

If you’d like to hear this podcast, you can go to Risky or Not (yes, that is co, not com). You can sign up to learn when they have new topics posted. Other recent program topics have been: Butter at Room Temperature, Reboiling Soup, and Salt Cured Egg Yolks. All past programs are available. If you have a specific question, you can also send it to the specialists.

If you really like this podcast, are interested in food safety, and would like to hear more, these two professors also have a longer (usually about two hours) podcast called Food Safety Talk. I look forward to hearing a new posting about every other week. You can check it out at Food Safety Talk.

This post was originally written for the Brunswick Beacon FCS Column on October 7, 2020. Cheryle Syracuse is a Family and Consumer Science staff member and can be reached at N.C. Cooperative Extension, Brunswick County Center at 910-253-2610 or by email at Cheryle_Syracuse@ncsu.edu.