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Typically I'll seal food for storage or sous-vide in a Ziplock bag, submerging it in water whilst closing the final inch to remove air.

How close to a machine seal is this, and is it worth worrying about both for storage and sous-vide?

Can salts be dissolved in the water or some other process to both increase the pressure of sealing and maintain a vat of water for longer without nasties growing in it?

With a ziplock under water, I feel goods without concavities seal perfectly and definitely don't crush the food. Plus of course liquids easily seal. Sealing soup bones however will have the plastic somewhat conform to the concave contours, but bridges are seen. Does the plastic somewhat stretch or bunch perfectly to the inner contours with a pro sealer?

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This method isn't really anywhere near what a machine would produce (and by machine i'm talking about a chamber vac not a foodsaver). You are just removing a significant amount of air from the bag by forcing it out through the pressure of the water but a true vac chamber can pull close to 1bar of pressure and remove nearly all of the air from the package. For storage the ziplock can be used for short periods if you take it directly from the bath to an ice bath and then to the fridge without opening the package. –  Brendan Jan 29 '13 at 16:35

2 Answers 2

up vote 4 down vote accepted

For storage, the biggest issue is whether you have a high-quality thick plastic bag that will prevent oxygen incursion. Have a few small bubbles inside isn't a big deal, whether you use the water method or a vacuum. But cheaper/thinner bags will allow oxygen in over time, and your bag will start to separate from the food, and you'll start to see ice crystals.

For sous-vide, I'm not an expert, but I think the biggest issue is that air insulates the food and prevents it from attaining temperature quickly and evenly. I think people who do home low-temp cooking recommending having a sauce or fat in the bag along with your protein to reduce the issues with bubbles. I do know that professional chefs will use the ziploc-in-water technique at home, with good results.

I don't think adding anything to water will affect the density/pressure enough to matter.

And yes, professional vac machines don't have this problem.

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Interesting point about the bag thickness. Do you think it's the plastic that has a porosity, or the seal on Ziplocks just isn't as tight? I was thinking the thinness of the Ziplocks was ideal was it allowed the plastic to conform easier. –  jontyc May 4 '12 at 22:26
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jontyc: According the the blog "Cooking Issues", the type of plastic used (polyethylene) forms a poor vapor barrier. Plastic wrap is worst, ziplocks are a little better, and freezer ziplocks are better than normal ziplocks. –  Steve May 6 '12 at 21:39
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if you have to go ziplock go with the freezer bags, they're thicker and deal with the heat better. –  Brendan Jan 29 '13 at 16:32

I answered a similar question in another post. What can I do to prolong vegetable and meat freshness in the freezer?

I store meat and seafood in the freezer for up to a year using a combination of really good plastic wrap and/or Freezer Ziplocs (Glad). I will even buy sandwich bags without zip locks for individual chicken breasts, and then put in a bigger freezer Zip Lock removing air again. Kind of like the commercial now. I helped my Mother do this when I was 8.

In late spring I try to do a major clean out and not buy anything until the frozen food is all used. It's easy to throw single chops or mix types of meat on the BBQ to rid yourself of the extras and make room for the summer fruits and new bargains. I even had something frozen for 2 years without any freezer burn or any bad effect on meat. I either stack flat and deep and/or double bag to give a buffer zone from the defrost cycle.

I leave the vegetable to the food market, and freeze where I can. Good plastic wrap will generally work for the odd shaped pieces. Read my post on the how to. I really like your idea to submerge in water for the concaved items.

If you are considering longer storage, then maybe purchasing professional machine is worth it. I just can’t deal with or have the room for another appliance and their supplies.

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