Freeze Dryers and Freeze Dried Food (Part 1)

[Cowboyartist]

Jim, you said not to turn the fd off between batches, keep it on so it will be cold.  How does one remove the ice build up without turning off.  I usually turn my fd off and let it defrost with the room air, usually takes about two hours,  I find that I can remove the ice with a knife after it softens and starts to fall off.

I don't us the defroster to remove the ice.  Thanks everyone for your comments. I am in Dayton, Wyoming and wondering if there  are any others on this blog in my area?  Let me know if you can.

[JimR]

Jim - a BIG thank you from me for that explanation of the cycles/timing. Definitely won't get a thumbs down from me when you make long posts (heck, I often drivel on and provide little to no info - yours are info packed!)

I have been bugging the poor guy I deal with at HR for some of that information - wanted to understand exactly what was happening so I can troubleshoot if necessary. I had already learned that the heaters come on at 500 mTorr and they go off usually around the 600 mTorr mark - but my last question was about whether the heater comes on at all during that initial untimed Cool/Dry cycle (particularly because I have had the timer come on at 0 minutes in and another time it wasn't on yet at more than 2 hours in so I was trying to figure out what was going on - and whether I needed to intervene).

 

My system has not yet gone up to your top number but I am not sure that is critical. It has however run a long time at your lower number (and even at xxx - meaning below the ability of the sensor to display) - I was told not to let it do that but it still seems to be ok if it runs a while on a lower than 500 mTorr setting though that does mean there is NO freeze-drying going on at all since the heater can't be on if the sensor is working properly).

 

I probably should not 'think' about any of this - I should just 'run' it (it is a great little FD'er and 'it' knows what it is doing) - but, I have this need to understand the process and at times that has caused me to overreact and stop the machine to check whether there was a leak I hadn't noticed 10 minutes prior.

 

If the screen displays "Drying" the tray heaters are on. If the display shows "Freezing" or "Cooling" the tray heaters are not on. The "Freezing" mode will have a count down timer showing how much time is left for the "Freezing" mode. The

"Cooling" mode will show a 00:00:00 timer which does not count down (or up). If you see ONLY "Cooling" with a count down timer you at the last 20 minutes (or whatever the timer shows) of drying. When this timer reaches 00:00:00 the vacuum pump will turn off and "Complete" will be displayed.

The top number (990) will be the first number the display meter will show. It will take about 4 minutes to display that number and then quickly goes to 980, 970, 960, etc. If you are not watching the display when this happens you will not see that number again. It shows only for about 1-2 seconds. Remember, 990 mTORR is very little vacuum, 700 mTORR is more vacuum, 490 mTORR is much more vacuum, etc. Your machine MUST pull a vacuum of less than 500 mTORR to FD your food.

When in "Drying" mode and the meter shows xxx mTORR you are pulling the most vacuum you can and this is fine. If the "Cooling" is displayed and the meter shows xxx mTORR this means your pump is not pulling any vacuum.

Yes, you could "not think" about it, however, the more you know how the machine and proccess is supposed to work the more effectively you can FD your food and get the max out of it. If you're not FD'ing large amounts of foods for long term storage and only FD'ing a very favorite things you can just use all of the defaults. If done 23 sessions so far and have 100's left to do to clear our my 3 freezers and in the fall my garden.

 

[JimR]

I'd add reseat the gasket and check the door seal.

 

Yes you are correct. When I "clean" my black gasket I completely remove it, clean the slit with a damp cloth, then clean the rounded part of the gasket, and reinstall. So far I have not had and sealing problems (yet).

[JimR]

Jim, you said not to turn the fd off between batches, keep it on so it will be cold.  How does one remove the ice build up without turning off.  I usually turn my fd off and let it defrost with the room air, usually takes about two hours,  I find that I can remove the ice with a knife after it softens and starts to fall off.

I don't us the defroster to remove the ice.  Thanks everyone for your comments. I am in Dayton, Wyoming and wondering if there  are any others on this blog in my area?  Let me know if you can.

 

Good point, let me clarify. I don't turn of the machine until I check all of the food for proper FD'ing. I leave it on just encase I want to put some or all of the food back in the machine at that time to continue to FD'ing. I might do this on things I have not FD'ed previously but most times if the food didn't finish I place that food in my freezer for later processing.

You are right. You can't defrost with the machine running. Like you I let the machine defrost on it's own without turning on the "defrost cycle". If I need to "turn" the machine around as quickly as possible I turn the machine off and carefully use a hair dryer to defrost. Don't overhead the chamber walls. It takes me about 15-20 minutes to defrost this way.

I also try to "time" my sessions so the food is done at a time I will be there when the machine finished. I have been awakened at 5am when the machine finished earlier than I thought it would. Since I didn't want the finished food to be left in the cold machine for many hours I got up and removed the food. That doesn't happen anymore. Got to get my beauty sleep. Since I'm retired I have the time to do this.

Not directly in your area but near, outside of Butte, MT.

 

Thanks to everyone for the feedback.

[Cowboyartist]

Jim,  Thanks for the update.  I am wondering if any one is having a problem that I just encountered.  I am getting oil in the vacuum hose.  I talked with HR and they had only encountered it one other time.  I have the pump sitting at the same level as the dryer with a loop in the hose.  The oil shows up in the lower  part of the hose loop.  I am guessing about two table spoons of oil. I appreciate any comment.  Mike

[Canon4me]

I received my FD a few days ago and due to my wife and I being so busy, we won't be able to unpack it and set it up until this Saturday. Is there any setup tips you can share that will help me avoid problems? During the evenings, I will start reading the 17 pages of posts in this thread.

I did have one question........I would guess the only packaging you could use for longterm storage would be Mylar. I currently use that for all my longterm storage from dry goods I get from Latter Day Saints storehouses. I see some of you are using those home shrink wrap / vacuum machines which I think will not preserve as well as Mylar, but that is just a conjecture.

[Deryn]

Cowboy - It loops up or down? Do you mean right at the pump end? Could you have put too much oil in the pump perhaps? Have you taken the oil out to be sure it is all oil (not an oil/water mix)?

My pump is on a utility cart on the same level as the bottom of the freeze-drier. The hose comes out of the FD side, loops down and then a bit up again to the pump. Is yours higher up than that?

Canon - Welcome to eGullet and our world of freeze-drying!

The setup instructions are really pretty simple and good as issued by HR - follow them and make sure that all your hoses/connections are tightened at the nuts with a wrench (after hand tightening). I use a large stainless pot for my defrost water - not anywhere near a 5 gallon capacity - but I find that is even more than needed so far - usually only get an inch or two of water in it. Clean the gasket well. Make sure to close the front door well - do that extra turn. Time your first run so that you can be there when the freeze cycle ends and the pump comes on (9 hours after setting the FD to on) - just to be sure it comes on and there are no leaks you need to address.

The only thing I did that is not in the directions (but I think was suggested somewhere in this thread) was to take the long twist tie that came around the electric cord and use it to very loosely tie a piece of paper towel over the exhaust so that if it mists, much of the mist will be caught in the towel. I left it slightly open at the side to allow air (and my hand) in and also bubbled it up so it doesn't rest on the exhaust hole area.

Good luck. You are going to love this machine!

Edited January 14, 2015 by Deryn (log)

[Scotch827]

I have been using my FD for a week. So far no problems except some exploded ice cream sandwiches . I was leaving the the ice cream sandwiches in the wrapper and cutting a slit about the full length of the sandwich. The only one that turned out correctly had an inch slit. I may try them with no slit and see what happens. I tried yogurt but really didn't like it dry, it did rehydrate ok. I did some raw venison chops and rehydrated them. They were very good fried. I also did a cooked venison roast it was good both dry and rehydrated. I have frozen corn I put up this summer. I cooked it with butter and then freeze dried it. It was very good dry and then rehydrated it tasted just as good, as well as sour cream and chive mashed potatoes. Frozen bell peppers from my garden were good both dry and rehydrated and fried with the venison chops. Banana slices and apples are just awesome for snacks. Tonight I have 3 trays of apples and a tray of Bryers ice cream . Tomorrow I am going to try some raw crappie fillets I caught today. I have been prefreezing the food and the machine.

[Kerry Beal]

I believe I was told that the ice cream sandwiches are more likely to explode if they are not frozen long enough and cold enough.  I always make sure they come from the deep freeze and I give them at least 9 hours of freezing in Freeze Girl.

[finishman2000]

I think I may have put to much in at once. I make my chili about twice a year and usually can some, retort some and freeze some. I figured with my new toy I would make some FD for on the go (use retort pouches most of the time for that) and loaded up all 4 trays. Well after 28 hours it was still in the second stage I figured there must have been a boat load of ice and I was right. I quickly defrosted and chipped the ice out, reset the freeze time for 3 hours and drying for 4 hours (it was mostly dry when I opened it up) for the final stage of drying.

This is kinda fun figuring out all the ins and outs of freeze drying.

[finishman2000]

I think I may have put to much in at once. I make my chili about twice a year and usually can some, retort some and freeze some. I figured with my new toy I would make some FD for on the go (use retort pouches most of the time for that) and loaded up all 4 trays. Well after 28 hours it was still in the second stage I figured there must have been a boat load of ice and I was right. I quickly defrosted and chipped the ice out, reset the freeze time for 3 hours and drying for 4 hours (it was mostly dry when I opened it up) for the final stage of drying.

This is kinda fun figuring out all the ins and outs of freeze drying.

[Deryn]

Scotch - If the ice cream sandwiches are wrapped in a plastic-like wrap, I would definitely make some kind of slit/opening in the wrapper. If you don't, there is nowhere for the humidity to exit during sublimation. I am not sure if paper is porous enough either to allow the water out.

I had an 'exploding ice cream sandwich' accident too. Cheap ice cream is what I thought was the problem - but not having them frozen enough I am sure isn't good either.

[Christopher N.]

I, like most of you, purchased a HR FD.  HR introduced me to this forum, which I have read through several times.  There is so much useful information here!  A big thank you to those that have contributed their experiences!!  I have completed a few cycles now, with some minor hiccups.  My first issue was with the vacuum pumps cord plugging into the back of the FD.  It just wasn't working consistently without manual manipulation.  To make a long story short, I widened the prongs on the plug a lot and now it seems to be able to work if I don’t move things around.  I’m still evaluating that situation (I have been in contact with HR and they will address it if it remains an issue).

 

Upon closing, the acrylic door doesn’t make good contact with the rubber seal on my FD unless I pull the seal away from the machine a bit after each time I open the door.  Only then will a sheet of paper not slide through.  As long as I address that with each batch it isn’t a problem.  For those that are new, when closing the acrylic door, make sure the handle latches, then turn the handle an additional 1/4 turn to fully complete the seal.  Like Tim P., Tango Charlie, and some others have done, I put a paper towel over the vacuum pump de-mister using a rubber band to secure it, and change it as needed.

 

I have noticed that each batch is a trial and error process unless I have previously done those same ingredients before.  Everything matters… the size of food pieces, the starting temperature of the food, the moisture content, the density of the cellular structure, the quantity placed in the FD, including the amount layered on each tray, etc.  I have started to error on the side of slightly longer freeze times and longer cooling/drying cycles (increasing each by 1-2 hours).  I love reading about and seeing pictures of what others have done.  They are extremely useful.  I won’t post my pictures (unless asked for) as they are the mostly the same items others have done.

 

Certain food items seem to be very popular, where as others aren’t as much.  I had some extra cooked chickpeas and steamed and cubed sweet potato (about 3/4” cubes) that I put in.  FYI, the sweet potato had to go in twice, as the skin seemed to cause a delay in drying (I would recommend either peeling, cubing smaller, slicing, or just set a longer cooling/drying cycle).  Has anyone tried FD’ing fish or shellfish?

 

Deryn asked about using acidulated water to dip certain foods in prior to FD’ing to prevent oxidation (browning or discoloring).  I put 2 tsp. of Fruit Fresh powder in 1/4 cup water to have a slurry to dip the fruit in.  It worked great for the apples, and I certainly should have used it for the pears.

 

I like a good sale and tend to stock up when I find one.  I will primarily use my FD for shorter term storage (1-5 years) of items that I have an abundance of, or other items that be can hard to come by at times (especially perfectly ripe), and also to thin out my many freezers (is that even possible?).  We eat out very seldom and I am the cook.  We eat a very diversified menu and I love to have items on hand from many different cultures at all times (which can be very difficult).  I harvest our garden and some fruit trees throughout the summer and autumn, so this will be a nice addition to my dehydrator and canning processes, perhaps even replacing them in many cases.  I have started storing my FD items in half gallon and quart sized mason jars and use our Food Saver to vacuum seal them.  I am, however, very intrigued by JimR’s process of sealing the jars by using the vacuum pump.

 

I will probably be using most of my items dry, as snacks or just to put into wet meals.  However, does anyone have a chart of how much water (by volume) they use for rehydrating various foods (by weight)?  I found this one (http://www.harmonyhousefoods.com/assets/images/default/PDFs/rehydrate_chart.pdf) but I don’t have any experience rehydrating yet, and I would be interested in seeing a reference guide that others prefer to use.

 

Thanks again for the useful information you have all contributed!!  I look forward to learning so much more.

[Kerry Beal]

Welcome Christopher.  

 

Your post got me thinking about how most of the stuff I use dry rather than reconstituted, but this morning I decided I wanted to make some imitation Boursin cheese, and didn't really want to go out to the grocery store for cream cheese.  I knew I had a lot of freeze dried cream cheese - so pulled it out, added some garlic powder, salt, pepper, fine herbs and some water.  

 

 

 

 

I may have added too much water - it seems a bit soupy - but I'll check on it later and see if it's firmed up a bit before considering adding more of the cream cheese powder.  

 

[Anna N]

Kerry,

Speaking of cheese… I am reminded that Christian Puglisi of Relae froze and then powdered Blue cheese which was sprinkled on certain dishes. He noted that even those who despised Blue cheese enjoyed it when prepared this way. At the time that his book was released he was just beginning to explore freeze-drying in cooperation with the University of Copenhagen. Perhaps by now he is freeze-drying it!

Edited to add:

Boursin cheese makes an awesome sauce for pasta and I bet it would work really well with zucchini noodles! Not that I am trying to merge topics but I do enjoy when one topic sparks a creative idea for another one. However, let's not allow this topic to drift off freeze drying/freeze driers. Comments about zucchini noodles should be in the spiralized vegetable topic here:

http://forums.egullet.org/topic/150390-spiralized-vegetables-and-vegetable-rices/

Edited January 15, 2015 by Anna N (log)

[Deryn]

Welcome to eGullet, Christopher. Thank you for the that link. I think, as time goes on, we may see this thread evolve (or a new one created) to talk about recipes which call for entirely (or almost entirely) freeze-dried ingredients.

Anna - I love that you strayed in here with a freeze-dried ingredient idea to complement the current topic on spiralizing vegetables. When I saw that thread, not only did it remind me that I own two spiralizers that I rarely to never use, but, it also got me thinking about freeze drying spiralized vegetables. They might be a bit fragile I fear but I think I may experiment with that concept soon anyway.

Edited January 15, 2015 by Deryn (log)

[Kerry Beal]

Except to mention that I spiralized a bunch of zucchini today and put them on a tray in the freezer to go with my next batch to be freeze dried.  There was a little space at the end of the tray so I added some spiralized swede as well.  I figure adding the raw FD vegetable noodles to the hot sauce will likely take the place of having to cook them.  Hope I'm right!

 

I should add a little blue cheese - perhaps I'll learn to like it.

[Scotch827]

I have been doing some apples. When I rehydrate them they would turn brown. I tried a few with some lemon juice and that did help. I have some asboric acid (vitamin c ) to try when I have more apples. My Bryers ice cream turned out good, better than most of the ice cream sandwitches. I dropped a piece of the vanilla ice cream in my coffee on a whim , it dissolved nicely and flavored it.

[JimR]

Finally !! My replacement FDer arrived, set it up and put a load in. Couldn't get the readout to move from XXXMtr. Bummer bummer!! So, rechecked all the fittings, the drain valve, the door seal. Still no go. Finally had my son-in-law check to be sure the vacume lines were tightened securely, he said they were. Tried it one more time and OMG! it worked!! Did my first batch yesterday and have my second going as we speak. First batch was pulled pork and green bean casserole. Came out great! I am on my way to emptying three freezers and downsizing those.

Peggy,

 

I just had this problem on my 25th FD'ing session. What we determined was there was enough water in the drain pipe to slow down the creating of a vacuum. As little as 1 ounce of water will cause a delay in your mTORR display coming off xxx. Even though you have been running the Freezing mode for 6-9 hours any water or mositure in the drain tube (from the bottom of the chamber to the valve) will NOT freeze. Another reason would be the food you put in the FD'er was not completely frozen. This is important for high water foods. If not completely frozen, as soon as the pump tried to pull a vacuum the unfrozen water will be pulled from the food. Without the water in it's gasious form it will not refreeze on the sides of the chamber. My problem appeared to be enough mositure in the drain since everything else tested OK.

 

The simple fix, if you think the drain line might have mositure, is to use a hair dryer pointed at the drain hole for a minute to remove any water. I just got of the phone with Pat at HR about this problem. Just when you think you totally understand how this thing works it throughs you a curve.

[JimR]

I did have one question........I would guess the only packaging you could use for longterm storage would be Mylar. I currently use that for all my longterm storage from dry goods I get from Latter Day Saints storehouses. I see some of you are using those home shrink wrap / vacuum machines which I think will not preserve as well as Mylar, but that is just a conjecture.

 

I'll give you may packaging reasoning. Long term (>3 or so years). Mylar with oxi absorber. Med term (>1 but <3) vacuum seal in mason jars with oxi absorbers and stored in dark place. This is to be used to refill my short term storage. Short term (<1 year) vacuum sealed in mason jars WITHOUT oxi absorber and resealed after opening and having product still left. This is used for day to day useage. I'm a believer in using what you preserve for normal cooking. Since you can use for FD'er to seal multiple jars at one time is can work very well (see my earlier post on vacuum sealing Mason jars in FD'er.)

 

Hope this helps. JimR

[peggy w]

JimR

I can see how water in the drain tube could cause a problem, however, it was the first load ever put in the FDer so that could not be the problem this time. Whatever it was, it is working now and I am more than happy with the results. Thanks for all the info and feed back  Pwilliams

Edited January 15, 2015 by peggy w (log)

[peggy w]

Just a note.  I ordered the Black Gold vacuum pump oil from Century Tool for less than 80.00 for 4 gallons. The shipping was over 30.00 but even with that it came out to about 7.00 a quart. The Black Gold pump oil was what came with my FDer vacuum pump so tried to stay with the same oil.

[Cowboyartist]

I have purchased 40 lbs of pears from bountiful baskets and they are almost ready to fd.  Have anyone had experience with pears, if so please advise, should I leave skin on or peal?  Any help is appreciated.  Thanks

[Kerry Beal]

I didn't peel my pears, I cut them top to bottom with a mandoline and FD'd the slices.  Of course I did this so I could dip them in chocolate.

[Christopher N.]

Cowboyartist, keep in mind that I am very new to all of this FD'ing stuff and I have only done pears once, but here's my experience.  I cored the pears and sliced them to about 3/8"-1/2" thick, leaving the skins on.  I ended up having to run them through twice as they were still wet on the skin end.  To do it again...  I would certainly increase the time on the drying/cooling cycle, as I only used the preset 7 hour cycle.  I would also slice them a bit thinner, but I still don't think I'd peel the pears.  I would also dip them in an acidulated wash prior to FD'ing.  I would put 2 tsp. of Fruit Fresh powder in 1/4 cup water to have a slurry to dip the fruit in.  If you don't have Fruit Fresh, you can use ground up vitamin C, or a diluted lemon juice wash.  This will help prevent the pear flesh from turning brown.  I only had one tray of pears and got them into the FD right away and they still turned a little brown.  40 lbs of pears is a lot and will take quite some time to FD.  As Mr. Mike has mentioned in the past, don't overload the FD, using a max of 5 lbs per load. He says even that can take up to 36 hours to FD.  If they are getting too ripe before you can FD them all, slice them up, dip in the acidulated wash and put them in a freezer (spread out on trays to keep them separated until frozen, then bag if necessary) until you are able to get them into the FD.