Make it Grolsch swingtops and you're in.LOL  I'm getting too old to drink bourbon.  It makes me feel like death anymore.

It'll be a while at least.  I soft probed the wife on the issue.  She seized up at mention of the price, but was still definitely interested in having one.   I told her that prices might come down over time, to which she quipped she'd be in at $400.  I told her 2k was more my trigger point, and she didn't get too freakish and only made a face.  Round one of verbal Judo complete, score one for Variable.  Purchase of freezedryer is established as desirable, and only the price acceptability has to be whittled away at from this point forward.  I'll give it a break for a while, then I'll subtly bring it up at opportune times.  Each time giving a reason or excuse to slide the acceptable price a little higher.  Once I hit her firm (even though irritated about it) price level I'll offer to sell something (that I was going to get rid of anyway) and make up the price difference.  It'll take a while to achieve, but I believe it'll be a accomplishable mission.

I think to score a complete mission success, I might need to sell an obsolete (to me) rifle, and then buy a newer one later to replace it.  I'll justify it by saying I'm using the money we saved by doing our own freezedrying!


ETA:  And thank the LORD that my wife doesn't read Arfcom!

Variable556, I also looked at some of the home built freezedriers on youtube amd realized that I might have half the components

TBS, from your pics I do not see that you are locked into using that rack set.  You might be able to set one of the trays on a rack recovered from a toaster oven...just tossing out thoughts...
For transport...cake box inside big big ziploc bag?  Might need to put packing peanuts around the flowers inside the box.  
I figure that the flowers would have to marketed to the consumer in a glass or acrylic display vessel that could have an O2 absorber installed out of sight.

Cool thread.  Keep posting pictures and what you do with it.

I would be curious as to what the refrigeration unit and vacuum pump model numbers are.

Looks to be a nice little machine.  Definitely worth looking into.

Been rationalizing one of these units for the last few days, I think I am at the point where I could buy one but I'd have to sell things to make it happen and I'm not sure I want to do that.

Part of my problem is that I already have a significant investment in freeze dried via the group buys that were happening in the 2000's, and some lucky purchases of .mil steak and pork chops-as in enough to have a steak every day for a year and a half....

I do have some bulk storage (not enough), some canned (not enough), and a fairly significant amount of dehydrated. Since acquiring it, I've met someone and that effectively halves my food reserves. As it is, we'd be fed for quite a while-but there's a difference between being 'fed' and being 'not hungry'. Like most households, we throw out a lot of food because she cooks a meal and it's just the two of us there to eat it. A lot of that food could be freeze dried and cost nothing more than the electricity and maintenance costs on the unit because we'd be throwing it out anyway.

$4k is a lot of bread right now.

i have been toying with the idea of building one for years now, so any details on components would be greatly appreciated.  Is there a one way valve in the vacuum line to prevent oil from coming back from the pump into the chamber?  What temp does the chamber that catches the vaporized water get down to?  What kind of cycle do the heating elements run?

I have 2 a\c compressors, condenser coils, an industrial vacuum pump and a chamber ready, but the finer points on how one of these actually works in practice have eluded me.

There should be 2 vacuum chambers.  1 for the food and a 2nd condensing chamber for the water vapor to resolidify prior to reaching the vacuum pump.  I'm guessing there is a drain for when this is defrosted, and some type of screen for the water to solidify on.  It needs to be colder than the food chamber to get the water into the right phase at the same pressure.

Does the vacuum pump run non-stop through the 24 hour process?

Thanks TBS.  Very helpful.  

I am disappointed in the lack of neopolitan ice cream

TBS, how did the steak chunks turn out?

Getting freeze dried fruit or ice cream otc is no problem...sheeeeeet even walmart and academy sell that.

On the other hand...
Getting freeze dried meat is a bit more challenging

More pics pls

What's the model number of the refrigeration unit and what are the units that your refer to as 400, 500, etc?  [MM-Hg, Torr, ?]

What 'Freon' or refrigerant are they using, it should be part of the data plate of the unit.


There is some lettering along the inside of the stainless chamber, what do they say?

OK, milli-Torr. Good info.

Basically the same as the old MM-Hg before they decided to make the unit of measure, Politically Correct, and comfuze everybuddy. Like they did with MHZ.  


Torr Wiki

Could you try dehydrating cucumbers  and see how they rehydrate?

Did I read somewhere you cant do this to onions? Man if I could do this with onion I would be one happy camper.

LDS has sacks of dried onions -cheap...

Also sacks of dried apples and bananas...

The lettering on the inside of the chamber is the ink stamp from the steel mill it came from.  Heat number, sheet size, alloy, etc.

I am now a happy camper.

It would be interesting to know what sensors and programming (as far as when to pull vacuum, when to apply heat when to run the cooling unit, etc.) are used. Seems like that might be the key to making one of these yourself. Most of the other stuff seems "off the shelf."

Yes, that's what I'd like to know...

Bah
Run a couple trays of onions and a tray of garlic...maybe a tray of leeks.  What could go wrong



On another note though.  Freeze dried salsa might be a real hoot

I've never thought much about home brew freeze drying but this thread interests me.  I spoke with a buddy of mine who used to work for Oregon Freeze Dry (Mountain House) about it and his first impression was that of curiosity because his only experience is with industrial sized operation.  

He told me a little about their process as he said it is not really a secret, just standard freeze dry process.  They use large vaccuum chambers that are about 6ft diameter x 20ft length and have I think he said there was 18 or so of them at the facility he worked at.  Each chamber has an arrangement of refrigeration evaporator coils inside them and another set of refrigeration evaporator coils in a small chamber in the piping between the vacuum pumps and the chamber to act as a vapor trap.  Each batch can remove about 2,600lb of water and that is what determines how much of what is processed.

The refrigeration system is a large centralized ammonia system with five LPR's (low pressure receivers) and the evap coils are set at -50F.  They prefer to receive the food from the suppliers already frozen so all they have to do is place the frozen product on trays and load the trays onto a large cart and wheel the cart into the vacuum chamber.  The carts have heating coils that circulate warm glycol to slowely heat the food after the target vacuum pressure is reached.  He said it doesn't matter how cold the food is frozen because "frozen is frozen" whether it is down to -40 or +10F.  As long as the food hasn't started to thaw before they get the chamber under vacuum it is good to go.  They want the food to start to thaw after the vacuum is achieved as this is how you remove the water.  As the temperature slowly rises in the food, the water changes phase from solid to vapor and is attracted to the much colder surface of the evaporator coils and forms a layer of ice.

Each batch takes about 4 to 6 hours and they do things to speed the moisture removal process like cycle on and off the vacuum pumps, inject gas such as helium and argon to speed the evapo-transpiration of the sublimated water.  He said they don't always inject gas, only when they are pressed to make production goals.  There are a few ways to determine when a batch is finished, mostly the operators just know that certain products take a specific amount of time and it is a set process.  They can also monitor the humidity in the vacuum tube to determine when moisture has been removed.  After the carts of food are done and taken out of the chamber, they flood the chamber with steam to quickly defrost the coils and drain the water out so they have a big boiler for steam as well.

Interesting stuff that I thought I would share.

Thank you, very interesting and aligns with everything I've picked up trying to glean "how to" online.  Lyophilization isn't rocket science, but the whole point of DIY in my opinion here is to save money, TBS machine is a good example of that, very small capacity, no vapor trap, and it's $4,000. (And that's the least expensive machine I've ever seen!)  One could source all of the components mostly new, for $1,000 or less, with the exception of a quality vacuum pump.  But at the same time, a guy could piss away all of his savings experimenting to get everything working in concert the way it needs to.

My BIL just passed the state HVAC cert, so now I can even get whatever refrigerant I need.  A little PLC board, some sensors and some elbow grease and I think I'm about set.

On, "frozen is frozen" I agree with your friend.  The point of freezing before reducing pressure is to keep the foods structure intact during sublimation.  If you were to introduce vacuum to unfrozen foods, the phase change tends to burst cellular walls and give you a product that is much further from "the real thing" on rehydration.  By heating slowly, it's my understanding that's able to be preserved.  Also, I don't believe the heat needs to be cycled on and off in any kind of pattern (although it should be tied to a set amount of vacuum to assure that any phase change is directly solid to gas and not liquid), because evaporative cooling of sublimation will tend to refreeze the items being dried.

Can you post some pics of the dehydrated food then pics of it rehydrated?

I wish I could afford one of these!

This is true as related to the phase diagram posted earlier.  You need to stay in the temperature/pressure range where water will directly phase from solid to gas.  It's a variable equation that doesn't require a constant temperature or pressure, but requires them to stay in relation to each other over a given range.

The third component to that equation, is on the larger, more industrial machines, with a third vapor collection chamber, which is required to be colder than the food chamber since they are both held to the same pressure.  If you want to condense the water vapor from gas to solid prior to reaching the vacuum pump, and the entire system is at 50Pa pressure, then the food chamber could be held at -25 F and the collection chamber at -50 F.  -25 F @ 50Pa would allow for phase change directly from solid to vapor, and -50 F @ 50Pa would allow the opposite.

Since yours is of single chamber design with the additional caveat of "change the oil often" I'm guessing the intent of the -50 F call out is to attempt to utilize the differentiation of temperature in the chamber itself to collect the vapor into the water.  I'm guessing the cooling coils are directly against the chamber walls, under that foam insulation, so the steel walls are colder than the center of the chamber where the food is, especially when utilizing periodic heating from the elements, and when that vapor comes in contact with the highly conductive walls of the chamber, it reverts back to solid.  Just not as completely as a (much more expensive) 2 chamber, 2 coil designed machine.

Awesome.

Thanks for the pics, OP.

It may be of value for you to know that with meats you want to put in only as much water as it takes to rehydrate them. I did this with a ziploc bag with the steaks I tested before buying in bulk. The problem is that the blood-which gives flavor-ends up in the water rather than the meat.

These are from my first attempts to rehydrate, and are the wrong way to do it:

Thanks for the warning