Hi all. I am thinking about using Freezer Zip-Lock bags to rehydrate my food. I did some research and found out about a company called Sorbent Systems that sells zip lock bags in bulk. Also, Enertia Trail Foods may sell their own zip lock bags in bulk as well. I'm also considering buying them from the grocery store.
My question is using a Freezer Zip-Lock bag from the grocery store or any of these other companies' bags safe? I'm not worried about the bag falling over as I plan to buy an outside support bag from R.E.I. or online to keep it upright and from falling over. What I am concerned about is whether the plastic will melt or if it doesn't melt, if the chemicals in the plastic will get into the food when the boiling water is poured inside.
I want to get away from having to carry the heavy and bulky dehydrated meals you get from R.E.I. i.e. Mountain House, Natural High, etc. because last year they took up too much room in our bear canisters. I plan to go light this summer and I want to use the smallest bear canister I can find or the conditionally approved Ursack with the aluminum liner. However, I want to find out if it is safe to use freezer zip-lock bags before I go. Has anyone here had experience with freezer zip-lock bags or with any of these other companies' bags? Did they work well or did they turn out to be more trouble than they were worth?
I don't know what plasticizer that the plastic bag manufacturers use, but one commonly used one is DEHP, a phthalate. There have been reports of phthalates being toxic in animals and you can search the usual sources to decide for yourself. The FDA is aware of these reports and has not banned DEHP, but I've heard that European agencies are considering it.
I have followed Bob's advice since 2005 and have never had a problem with pouring boiling water into the pouch (and yes, a support mechanism can be useful since the bag does get rather hot and a little unstable).
When I buy dehydrated food, I remove the contents from the original pouch and pour into the zip-lock freezer (buy the kind that indicates "use for freezers" since most people also either heat them in microwaves or place them in heated water).
With a black pen (magic marker, I write "contents", number of cups of water, and simmering time. I'll tell you this, the amount of space that you can save in a bear canister it tremendous. I have been on 8 day trip with all my food in one canister.
Last year when I hiked from Horseshoe Meadows to the Portal, I used the small bear vault canister and still had room. This for 4 days.
I usually take the Mountain House and Alpine Aire freeze dried products from their original package and put them in a zip lock bag for later re-hydrating. I carry a single outer package to retain heat during the process but I have been able to squeeze 7 to 8 days of food into a Garcia Bear Canister by re-packaging.
I sometimes use my Foodsaver.You can totally customize the size of the bag then vacuum seal it.Makes it compact and you can still write what you need to on the outside.Very good and stable when you add hot water.It's just not a resealable bag after you cut it open unless you use twist ties.
Hello to everyone who responded to my inquiry. Your responses were helpful and allayed my concerns about pouring boiling water into zip-lock bags. Thank you very much.
Also, at higher altitude pouring boiled water into plastic bags is less of a problem because it doesn't get to as high a temperature . (194F at 10,000' and 190F at 12,000', compared to 212F at sea level.)
I dehydrate a lot of my own food, and use freezer ziploc bags with no problems. I do suggest using your camp towel to wrap it in while waiting for it to rehydrate, as it loses heat quickly. Sometimes it helps to knead the bag occasionally too.
The "Lipsmackin" backpacking recipe books have good advice on ziploc usage, as well as some excellent recipes. I have a review of one of them on my backpacking blog: Lip Smackin' Vegetarian Backpackin'
because it doesn't get to as high a temperature 
. (194F at 10,000' and 190F at 12,000', compared to 212F at sea level.)