Thawing Individually Quick Frozen (IQF) fish
Well, this is sort of about food, but more about process or maybe food safety. I like to keep a few hunks of individually vacuum sealed and quick frozen tuna or salmon in the freezer for times when I feel like eating fish but haven't gone to the fish market. I've seen some cook-from-frozen instructions, but they don't seem to work out too well for me. I like to thaw it, season it, and then grill it.
When I first started buying fish packaged this way, one of the methods for thawing that was printed on the label was to just toss the sealed package in a large bowl of cold water for 20-30 minutes. It works fine, it's not messy, and it's quick. Now, I'm noticing that several packages (depending on the source) say "Must remove from vacuum packing before thawing."
What's up with that? Is this a safety thing like bacteria stuck to the wrapper might contaminate the fish? Or do they just expect you'll nuke it on 'defrost' and they don't want it to blow up in the microwave oven? Or something else?
I've just kept doing what I've been doing and it hasn't killed me yet. I'd just like to know why the change in directions.
So I ran across your post searching for research articles on fish (grad student here), and let me tell you there is a most definitely a safety reason for thawing while chilled. I hope that you haven't gotten sick from any fish in the time that you first posted!
Fish is well-known to contain many types of bacteria, but it is vacuum sealing that can bring out the biggest bacterial pathogens of any food product. In your case, Clostridum botulinum is the highest risk pathogen in that setup, and for good reason, it's one of the deadliest. Fortunately, so long as you thaw it while chilled, or very quickly in the microwave, you should be fine. A few hours at any temperature above 50F and you got yourself a serious potential for intoxication, and I wouldn't suggest any other course but to discard (that includes freezer malfunctions).
Just a food scientist reaching out, and cheers to fresher food!
Gas buildup. Whether it's from the bacteria in it or just regularly occurring from decay, dead flesh will give off gas (Also expansion like someone throwing it in the MW like you mentioned). It's really one of those silly things that shouldn't be needed, but is. Unless you're going to be "defrosting" it for days, there's nothing to worry about.