Where I live is currently in Covid lockdown, so when I was cooking dinner tonight, I decided to pull some old hot dogs out of my freezer and boil them. However, rather than sinking to the bottom of the pot, they floated, and during the boiling process, a sort of yellow foam could be seen coming off of them through holes in their skin. Finally, when I removed them from the pot after they'd been boiled, I noticed that they were unusually firm, and when I cut one open, the meat (or fat?) inside had gotten a bit of a yellowish hue.
When I checked the packaging, I saw that they'd had a best before date of 2019. While they had been in the freezer that entire time, and had never been defrosted, so I didn't have to worry about them going bad from bacterial growth, but I remember hearing that frozen meat can go rancid from oxidation over time.
Is this what happened to my hot dogs? If so, would they have been safe to eat? Is there any way to tell if frozen meat is starting to go rancid, so that it can be eaten before it goes fully inedible? I figured "better safe than sorry" and threw them in the rubbish bin, and made myself something else to eat instead, but now I'm sort of wondering about what I should do in the future if this recurs.
Best Answer
When storing meats in the freezer, it is not generally recommended to extend the best before date by more than 4 to 6 months, depending on how much before the best before date the product was frozen. The link posted by Carina in the comments gets it bang on.
There are several reasons for this, but the biggest one is probably sublimation, more commonly known as freezer burn. The low temperatures in your freezer slow down the evaporation of liquids in your products, but don't stop it entirely. This means that the liquids in your products evaporate, leaving you with dry rubbery leftovers. You can notice this when your hotdogs feel firm and slimy after thawing, as the evaporating moisture draws the inside oils out with it. When boiling, they will indeed float as the moisture inside has been replaced with air. They might very well foam yellow, as the now freeze dried ingredients that were mixed with the moisture now recombine with the cooking water. (Fun fact, a controlled version of this mechanic is used in a process called freeze drying, which is used to produce instant noodles, coffee, or any kind of "Just add water" products on the market).
The second is the one you named, known as lipid oxidation. This is the normal mechanic of meat spoiling, and is again slowed down by the freezer, but not entirely stopped. This kind of spoiling in the freezer is more common in processed meats like hotdogs and sausages, rather than whole cuts. This is because processed meats have several additional ingredients making them "impure", these additional ingredients give the meats a less dense structure allowing for faster sublimation and increased spoiling. Whole cuts can commonly be kept in the freezer longer, up to a year in some cases.
The last reason is a minor one, but not to be disregarded. A well used freezer is opened several times a week, or even several times a day. This means that the products inside are regularly exposed to fresh air with live bacteria. Again, freezers slow down the working of bacteria, but don't stop it altogether. When a product is supplied with fresh bacteria regularly, the product will be contaminated beyond the safe point eventually, it is only a matter of time.
That being said, if even from a food safety standpoint your meat would be safe to eat, the freezer burn alone would make your hotdogs rubbery, dry, and tasteless, and there is very little chance you would have enjoyed eating them at that point.