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Home Forums Technical Discussion Freeze drying food

This topic contains 25 replies, has 4 voices, and was last updated by  caverdude 5 years, 2 months ago.

Viewing 15 posts - 1 through 15 (of 26 total)
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  • #36860

    caverdude
    Participant

    Does anyone know if this can be done at home easily? Is home freeze drying equipment available?

    Basically you pump a vacume on a chamber which has something to be freeze dried and of course you freeze it at the same time. Where does the moisture go? This probably requires air ciruclation and somehow the moisture condences outside the chamber? Hey a great way to produce drinkable water also right?

    #41545

    WrethaOffGrid
    Keymaster

    The short answer is probably no, I did some research on it (the same research you or anyone else can do, I don’t have access to any special info), I had hoped it would be something that could be done, but I can’t see a way to do it. Yes, the moisture does have to have somewhere to go, quite frankly, without major equipment that most of us don’t have access to, nor could the average person afford it if you could access it, it’s just not feasible.

    I wrote an article on it,

    http://www.www.off-grid.net/2011/02/21/freeze-dried-vs-dehydrated-foods/

    You might be especially interested in the comments on that article. Now, if you, or anyone else, figures out a way for the average (or even the not so average) person to do this, please post a message about it, it is something that I would be greatly interested in. :)

    Wretha

    #41548

    caverdude
    Participant

    I think your article is what spurred my question. Maybe I need to read it again. But a/c and refrigeration units remove moisture, so I guess a freezing unit would do the same. When you cool air, it is like squeezing a sponge, moisture condenses somewhere. Usually at the location where it is being cooled. I wonder if there is a warm/freeze/warm/freeze cycle going on which keeps drawing out water.

    I am fogetting that there is a vacume, and not circulating air. I see the problem now.

    http://larrydgray.net

    http://larrydgray.wordpress.com

    #41549

    caverdude
    Participant

    Well, is the problem with home freeze drying maybe the temp which you must freeze to get the evaporative effect? I don’t think the vacume would be expensive to setup.

    For example does the temp need to be -60 or lower? This would be difficult with any home freezing equipment. Could dry ice be used in an experiment to achieve lower temps?

    I can see the possibility that it might not be feasable in small quantities such as 5 quarts of stawberries vs 1000 quarts. So that only freeze drying in larger quantities would be worth it.

    Maybe 4 families could go in on a comercial freeze dryer and share it.

    http://larrydgray.net

    http://larrydgray.wordpress.com

    #41550

    caverdude
    Participant

    After a quick read of the wikipedia article on freeze drying I see that food stuff must be quick frozen to between -60f and -110f roughly. I once worked at a tyson chicken production facility. They used large conveyer vegetable freezers to quick freeze chicken parts. They call it IQF Chicken. These freezers were set on -60 and the product entered at around 55 degrees, it remained in the freezer for 10 to 15 minutes I think. Freezing something this fast does not destroy cell structure because no ice crystals form.

    http://larrydgray.net

    http://larrydgray.wordpress.com

    #41551

    WrethaOffGrid
    Keymaster

    Hmmm, caverdude, I’m thinking liquid nitrogen for quick freezing…

    Wretha

    #41554

    elnav
    Member

    Wretha,

    flash frozen does not have to use nitrogen or dry ice. But it does use a lot of power. The unit I wired up on a fish tug needed 3 phase power of about 35 kilowatts. The vacuum pump system also uses a lot of power which is why home dehydrators are popular.

    The food saver system which is available as a consumer item is the closest approach that is cost effective and can be used at home. Many of my boating friends use these and report fresh foods can remain stored for six months or longer. The catch being if they do not remain frozen they can spoil at room temperature.

    Commercial freeze dried coffee on the other hand can be stored at room temp then reconstituted by adding water. Ditto for camping food packs. The chief advantage being you can store it without power and by removing the water it is lighter to back pack.

    #41558

    caverdude
    Participant

    A quick search on ebay reveiled some freeze drying equipment for sale from $200 to $8000 I think. But yes if any of it requires 3 phase this could be a problem for a home solution. It might be that if a person owned a small business or shop with 3 phase then it wouldn’t be such a problem for them.

    #41561

    elnav
    Member

    Just because you can do it does not means you should. Freeze drying is a technically complex and power hyngry process. Compare this with dehydration which can be accomplished (sun dried) without using power. Both processes result in food packaged so it can be stored without refrigeration.

    Using your numbers of $200 – $8000 I can buy a lot of freeze dried supplies for that amount, without needing power and having huge power bills to pay.

    #41563

    caverdude
    Participant

    True that. Its probably not something a person should do unless they intend to share, distrobute or sell the food. I always like ot know the “why’s and why not’s”. Curiosity.

    http://larrydgray.net

    http://larrydgray.wordpress.com

    #41564

    caverdude
    Participant

    Next thoughts.

    1. Could a hydro site produce 3phase for a micro freeze drying operation.

    2. Does dehydration and freeze drying remove same amount of water percentage wise?

    3. Is freeze dried food lighter than dehydrated food? I’d say no if the water content is the same, you might even think dehydrated would use less space than freeze dried.

    http://larrydgray.net

    http://larrydgray.wordpress.com

    #41565

    elnav
    Member

    #1 yes most alternators are designed to deliver 3 phase power but rarely in the quantity needed for freeze drying. It is the diodes (rectifiers) that converts it to DC.

    Water turbines intended for driving electrical loads are often wired for single phase. The reason being most consumer products are single phase. Many residential electricians are unfamiliar with 3 phase and are reluctant to get involved. We are seeing more and more big yachts (100 feet and up ) with 3 phase power becaause it is much more economical. I did a design for a 127 footer several years ago which was just launched. It had 3 phase power. When I was aboard a Coast Guard cutter I noted that it was wired 3 phase. Incidentally it had no battereies for starting. Instead they used compressed air. Where 120V light fixtures were used they always installed three lights in a group. Each 120V fixture was connected on a different phase.

    #41567

    caverdude
    Participant

    Well the project is becoming more and more expensive, but I really love the taste of freeze dried foods haha.. Maybe it was the MRE’s and freeze dried beef and pork patties that made me addicted. Not to mention peaches and pears and srawberries.

    http://larrydgray.net

    http://larrydgray.wordpress.com

    #41569

    elnav
    Member

    project ????

    Maybe we could help better if we knew what exactly the project entailed.

    If the object is simply to get freeze dried foods why not just go buy it.

    If the object is to go ‘bunker mentality’ and prepare for 2012 survival mode where you have to manage after the earth stands still that’s another matter.

    In that case you need to completely revise your thinking about reliance on ANY technology. That being the case I suggest going to low technology magazine or its companion publication ‘No technology’ magazine for ideas.

    My goal in going off grid is being able to live in places where the power lines have not reached as yet. Its nice to occasionally get into town and enjoy some of the benefits of moderen tecnology. Soft ice cream is something rather difficult to make economically off grid. Although my wife is a superb cook a nice italian dinner is also a nice change. Even if she can serve moose 101 way and makes a delicious salmon quiche sometimes a good restaurant meal would be nice.

    #41571

    caverdude
    Participant

    Make-believe project. Just dreaming a bit. But yes, emergency survival and self sufficiency would be the larger goals.

    http://larrydgray.net

    http://larrydgray.wordpress.com

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