How feasible is it to repack freeze-fried food? Thrive sells freeze-dried individual ingredients (broccoli, chicken cubes, etc.). This is really useful for people with dietary restrictions. It occurs to me that I could take it one step further by mixing the ingredients ahead of time into individual meals. Has anyone tried this?

I have two questions, and possibly more as I think about this --

1. How long would the "individual meals" last?

2. Would I be able to increase the lifespan with some sort of vacuum pump? What procedure would be best?

I can't think of any reason you couldn't do it. Shelf life should be good but not as good as if you left them unopened. This is assuming they're pasteurized/sterilized to begin with. You could probably get pretty good life by vacuum sealing them (again, not as long as they originally had). I wouldn't worry about them spoiling within a few months.

When you repackage some bacteria will get in that can lead to spoilage. However, the AW (water activity) will be very, very low in freeze dried food.

This might sound kind of nutty but if you have a decently stocked "modernist kitchen" you could use a vac sealer (preferably a chamber vac machine) to seal them, then sous vide the bags to pasteurize them. I would think that should extend the shelf life even further.

That doesn't sound nutty at all, Phaedrus. I do have a vac sealer, but it's the cheapest kind (little pump sucks air out of plastic bags with one-way valves). Alas, I'm scared of doing sous vide. For cooking, it requires more precision than my meticulous self could handle. I also worry about heating plastic.

How can I figure out shelf life? Just wait and see? With freeze-dried food, will I the average smell and taste test work for detecting spoilage after reconstituting or cooking it?

I think Phaedrus was referring to sous vide as a means of pasteurizing the resealed bags. There should be no problem with the plastic that the sealers use. they should easily be able to handle temperatures hot enough to kill the bacteria that may have been introduced during the repackaging process. You only need about 180 degrees (to be on the high side). I saw a show where a chef stated that you can cook ribs in regular plastic wrap (Saran Wrap (tm)) at 200-225 degrees because it does not melt until right around 400 degrees.

Actually you can pasteurize at 130 F, it just takes several hours. I do a lot of cooking at temps between 130-145 F, and with sous vide I rarely go about that (the only thing I do higher being dark meat chicken, which tastes undercooked at temps under 148 F).

I appreciate your concerns about heating plastic, but the food you buy (eg Mountain House) has already been heated in plastic. Everyone has to make those decisions for themselves but with modern BPA-free bags designed for cooking I think the risk is minimal, especially when you keep the temps far below boiling. I don't think much will "leach out" of plastic at 135 degrees F.

I'm not sure how you could hope to "calculate" shelf life if you don't sterilize or pasteurize. The latter results in about a 6D reductions in all pathogenic bacteria. The math would indicate that food prepared in that will last for weeks/months, with many variables. Not much may to be sure if you don't heat treat them.

Pretty much all the common bugs that cause food-borne illness (eg. listeria, salmonella) need most of the same things we do in order to thrive. They aren't killed by lack of water but they can't grow/multiply/reproduce without it. That's why drying food preserves it. Of course, salt also inhibits bacteria. Lastly most bacteria need to have a comfy pH level, too. When you think about salting, smoking, pickling, and drying this starts to make sense.

Bacteria basically need the right temperature to survive. Salmonella, for instance, is killed by a few seconds at 165F. However, it's also killed by temps above 130F...but it takes a lot longer. That's the point of sous vide. Holding food at, say, 140F will do the trick by killing the vast majority of bacteria (maybe 5D or 6D) but not all of it. That's why pasteurized milk, though treated to kill most of the bacteria, will still spoil if you leave it on the counter.

Beyond this level we have sterilization. A hospital might use an autoclave for that. Industrial food processors will use giant "pressure cookers" to heat food up to around 245-250 F. At this temperature essentially everything is killed. That's why canned food or aseptic juice boxes or "shelf stable" milk can be stored in the pantry.

I think it depends on what you plan to do with the food. If you want to open the big cans and vacuum seal packages to take on a two week canoe trip I'd feel pretty confident it would work fine with no additional cooking. If you want to build a stash of small meals for TEOTWAWKI it's probably not idea; for long term you would really have to do some real heat treating.

I wonder if after transferring loosely to a transparent bag if ultra violet light might be an option...you could shake the contents around for several doses... temporarily closing the bag, and then vacuum seal...... I used a safety goggle UV sterilizer in my classroom... in 30 years only replaced the bulb once..

Maybe. I don't know much about UV sterilizing. It's used in the dry aging of beef, but it's nothing I've ever done.

i had bad luck with freeze dry chicken.i got a #10 can of the chicken chunks and made up zip lock bags of single servings for a solo canoe trip.no vacuum packing but they went right into the freezer for a week or so.
the first night out i hit camp late and cooked the chicken in a pot of Knorr rice side.being hungry i may not have cooked everything long enough only letting boil a minute and simmer until the rice was soft,a few more.i had stomach problems the next day and stayed in camp.i did not use the chicken again but i did use ground beef that i fried in a dry pan and ran thru a dryer until it was like dog kibble.that went into rice sides and i had no problems.i had a few extra meals for wind bound days so i never was short on dinner.

"I wonder if after transferring loosely to a transparent bag if ultra violet light might be an option"
It would probably depend on how deep the U.V. light penetrated. I would think something like meat would not be conducive to good light penetration. Given the consequences of eating bacteria laden foods, I would regard that with extreme prejudice until someone shows it's efficacious.

JPickett... I was referring only to already freeze dried food, that may have become contaminated in the transfer to a vacuum sealed pouch...however, your caution is probably the best advice...

UV light works to kill bacteria while aging meat but with primal/subprimal whole cuts, nearly all the bacterial load is on the surface. I would think it would be hard to expose every surface to light if the food was composed of small bits. But I can't say for sure.