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Why didn't my stock freeze?

Made a huge double batch of stock Sunday, portioned it out on Monday into freezer bags. I did all of the portioning at one time into one-cup, two-cup or three-cup portions. The one-cup portions went into pint bags, the two- and three-cup portions into quart bags. I laid them flat, stacked in two piles, in the freezer on Monday night. Last night (Wednesday) I went into the freezer for something else, and the top bag in the pile, a three-cup bag, was not frozen. The bag immediately below was frozen solid. I checked the other bags, and two of the two-cup bags in the middle of the piles (with frozen stock above and below them) were not frozen. All other bags were frozen solid.

As I said, I did the portioning out at one time. I strained the stock before refrigeration, and then I skimmed the fat after refrigeration, so it should have been fairly homogeneous.

So my question is, why would three bags of stock have not frozen when all the others did? I'm hoping someone will have a scientific explanation; otherwise, I might have to blame aliens for messing with my head.

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  1. so the outer bags were not frozen, I suspect that your freezer is not cold enough were the outer bags are exposed to warmer temperatures from opening and closing your freezer door.

    Also, the defrost feature could be defrosting the outer bags while the inner bags are insulated by the outer bags.

    My suggestion is to set your freezer to a colder setting.

    1 Reply
    1. re: dave_c

      One outer bag was not frozen, and it was closer to the back of the freezer than the front. The top bag on the front pile, which was as high as the back pile, was frozen solid.

      It's a chest freezer, and everything else in the freezer was frozen solid - I checked because I was concerned about the temperature. I only open it two or three times a week tops. It does not have a defrost feature - it must be manually defrosted, i.e., scraped or cleaned out and turned off to drain.

    2. It's difficult to say without any experimental data. My first guess would be that the freezer is not cold enough.

      Another possibility is that the non-frozen bags of stock had more impurities (e.g. salt) than the other bags. Impurities lower the freezing point, so your freezer needs to work harder to freeze everything.

      Finally, the freezing process actually release heat while the water is transitioning from liquid to solid form at 32F/0C. This is called "latent heat". In some citrus growing regions, they actually spray the orchards with water when freezing temperatures are expected. As the water freezes, it release energy into the surrounding air to keep it from dropping below 32F/0C. Perhaps the frozen bags released enough latent heat to warm the other bags.

      3 Replies
      1. re: raytamsgv

        I did not use any salt, just the usual stock ingredients - onion, carrots, herbs, etc. I'm liking the latent heat idea. There has to be a scientific explanation, and this makes sense. It also serves as a caution for the future when I freeze other foods - I won't stack non-frozen foods higher than two at a time; instead I will spread them out until they are frozen, then stack them.

        1. re: lisavf

          It's not just salt that lowers the freezing temperature. I know that alcohol will have the same effect. I'm *guessing* that other impurities (i.e. anything aside from water molecules) will have some affect on the freezing point.

          1. re: raytamsgv

            Impurities would not prevent freezing by that much to prevent freezing in a deep freeze. Even salt would have to be high enough that the food would be inedible by almost all.

      2. Was the stock cooled when you put it in the freezer?

        1 Reply
        1. re: Terrie H.

          Yes. I took it from refrigerator to bags to freezer.

        2. Chest freezer and it did not freeze. I would think that anything you put in there except maybe vodka would freeze in a deep freeze if it was working correctly.

          1 Reply
          1. re: cacruden

            Exactly. That's why I posted the question - everything else in there is frozen solid as it should be.

          2. I can't think of anything in the stock that would keep it from freezing over four days. Is it still not frozen?

            1 Reply
            1. re: scubadoo97

              As of last night, one bag was still not frozen. As of this morning, all are frozen solid. Weird!