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Jan 21, 2013 11:03 AM

Vacuum Sealed Produce in Mason Jars

I've been vacuum packing fruit and vegetables in both mason jars and bags and storing them in the freezer. I've noticed that the jars will accumulate ice on the sides of the jars and on the fruit/vegetables. But, the bags don't accumulate any ice.

I've been under the impression that vacuum sealing will eliminate freezer I don't understand why the ice would accumulate in the jars but not the bags.

Can anyone help with this? Will the ice affect the taste of the produce in the jars even though it's vacuum sealed? I'm sure there's an easy scientific explanation to this, but I'm not aware of it :)

Thanks for any help.

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  1. I expect it's just that there is more air, hence more water vapor, left in a jar after vacuum sealing than in a bag. You can't create a perfect vacuum.

    2 Replies
    1. re: GH1618

      I agree. I think you can pull out more air from the bag since the bag collapses to push air out, while a jar has rigid sides.

    2. Hi. The three of you are on to something, and then again you're not. There is something else going on her.

      The thing is that vakuum in a plastic bag and vakuum in a jar are actually two very different things. In the first case, the bag will just collapse around jour food, remove every pocket of air nicely, and thereby removing the ice's possibility to evaporate anywhere.

      In a jar, on the other hand, you create a vakuum chamber around your food.
      This is exactly how you would go about to make freeze dried food! The water will want to move from where it’s consentrated (your food) and try to populate the void you created.

      Have you ever heard how water boils at very low temperatures at higher altitudes? You're creating the same effect in your jars there.
      If you had a NASA grade vakuum pump and made a very, very, very good vakuum, you could make water boil at minus 68 C (-90 F).
      So you see the vakuum in the jar doesn't preventing your food from drying out at all. It actually dries it out a lot faster.

      I suppose freezing the food in a pressurized container would be a way to avoid evaporation. I haven't heard of anybody selling equipment for that yet, but someone will try now. It'll probably be the next fad. If so: IT WAS MY IDEA!!

      5 Replies
      1. re: Grunde

        You are correct that water in the food will evaporate into the vacuum, so there will be ice regardless of the quality of the vacuum. I expect this is a small effect, because the space is small and sealed. To freeze-dry food you would need to remove the moisture from the jar. It's the sealing of the jar that prevents freezer burn. Evacuating the jar removes oxygen, however, which helps preserve the food.

        1. re: GH1618

          You're right, of course. I don't deny that the air poets is the reason for the snow in the first place.

          But the question was why the ice accumulates in the jars and not in the bags.
          My answer to that, to be clear, is that any air pokets will accumulate snow. In addition to that, the vacuum doesn't counter the snowiness, it actually makew the problem worse. Then I attempted to explain what a vakuum does in a way I hope most people can grasp.

          However, I don't agree that the effect of the vacuum is necessarily marginal, as you state.

          Anyway, I don't see steph995 mentioning anything about how much "air" there is in the jars. How do you know the air pockets are small? If he/she is freezing sliced fruit, I would imagine there's quite a lot of air pockets down there. The more air - the more snow.

          1. re: Grunde

            I'm just assuming that the air volume is "small" compared to the volume of any freezer. Even if a jar were half empty, it would still be a small volume of air. But I'll reserve final judgement until I do a controlled experiment. I'll need three jars with identical contents, one vacuum sealed, one sealed at normal air pressure, and one unsealed. What do suggest would be the ideal test material, and how long should it be frozen to expect the effect of "freezer burn" to be readily noticeable?

            1. re: GH1618

              Cool. You go!
              I reckon both on chicken breasts and salmon the freezer burn stands out like a sore thumb.

            2. re: Grunde

              It was actually sliced fruit, and the jars were about 3/4 full.

              I look forward to reading about the results of your experiment.

              thank you all for the input!

        2. I often freeze produce in glass jars although I’ve never used a vacuum seal method. Here’s a tip that works for me.

          Chill then freeze your produce on a baking sheet before you store. This reduces ice crystal formation because freezing warm produce creates condensation. You will still have some ice crystals but it will be much less. I give it a quick rinse after thawing and the taste is fine.