Freeze Dryers and Freeze Dried Food (Part 1)

[dbinokc]

Kerry,

After you dip freeze dried food into chocolate, do they stay crunchy or go soft. If they go soft, do you need to keep them refrigerated so they do not spoil?

[Kerry Beal]

They stay crunchy - the chocolate contains no water so it keeps them from getting soft (as long as they are completely covered).  I don't need to refrigerate - keep at room temperature.

[dbinokc]

Is there be anything non-chocolate that could coat something freeze dried and keep it from absorbing moisture. 

[Deryn]

dbinokc - Since chocolate is really a very short term solution (and subject itself to degradation from heat and time), chocolate is not going to make FD'd food last very long outside of a good storage container (glass/mylar/metal) with an O2 absorber, etc. The thicker the coat, the longer it would last however. Kerry could probably address that better than I can.

 

I guess you could coat it in wax - but, you would have to peel it off to eat the contents.

 

I am not sure what immersion in honey would do for a freeze-dried food but I suspect it would go soggy over time even if there was no oxygen - perhaps moisture would be the reason.

Edited January 18, 2015 by Deryn (log)

[Chocolot]

Is there be anything non-chocolate that could coat something freeze dried and keep it from absorbing moisture. 

 

I guess it depends on your purpose. Kerry coats in chocolate, not as a way of preserving, but for creating a unique confection. If you are looking for a confectionary coating that doesn't contain cocoa products, there are several. None worth using IMHO, as the taste suffers.

Edited January 18, 2015 by Chocolot (log)

[finishman2000]

don't know if anyone else has used this but it works great for filling mason jars as well as bags. It's a parts tray that I pour the FD tray into or my measured out portions into then just open the bag and pour the amount into. I just did a boatload of chili and I measured out two cups of fd chili into the tray then easy breezy pout it into my 6x10 chamber sealer bags. 

 

http://www.harborfreight.com/easy-sorter-funnel-tray-37081.html

[Kerry Beal]

Brilliant - that would be great for filling bags in all sort of applications.

[cyalexa]

Brilliant - that would be great for filling bags in all sort of applications.

Looks rather like the bottom of a pill counter. Ask in your pharmacy, they probably have lots as they are common freebies from reps. 

[Kerry Beal]

Ah yes - and the pharmacy ones would fit into a small bag top as well!

[Kerry Beal]

Host's note: this post's first paragraph refers to a series of posts suggesting ways to bring order to the chaos developing in this topic. Those posts have been moved to the Moderation and Policy Discussion Forum, in a new topic. Interested members are invited to read and participate in that conversation. Please focus posts in the present topic on the subject of freeze dryers and freeze dried foods.

We'd best get back on track on this thread - management on eG is going to look into something 'pinned' covering what Mike has suggested and others have put input into that will hopefully serve the purpose. So for now - this thread can serve to cover what we are making.

I have to confess that I haven't done anything for a while - we are working on some wiring in the house and I keep thinking that it's actually going to get started and interfere with a run - so about 5 runs could have been done while I waited!

Meantime in the freezer waiting to go I've got some spiralized veg, some ragu and some more fruit.

Edited January 19, 2015 by Smithy
Host's note to point to new discussion, in appropriate forum. (log)

[MelissaH]

I just want to say that yinz are all making me wish I had the time, space, and money for a freeze dryer. Alas, it's not happening any time soon, so in the meantime I'll just have to live vicariously through you.

 

Kerry, I'm curious whether the spiralizing is important for the fun spiral shape or just because it gives you more surface area from which water can get extracted. Would shaving veg with a peeler be as effective, albeit less pretty?

[Kerry Beal]

It's the fun spiral shape - imitation low carb noodles actually!

[finishman2000]

Trying to speed things up as much as possible, I have made a 8 tray holder for my freezer with some scrap material and some threaded rod. I'm using corrugated plastic as the trays. Frozen food comes right off. I cut them slightly smaller than the trays so I know what fits on the tray will fit on the factory ones. When doing food that stick I use parchment paper that I slide off the plastic right into the metal one. I take off 3 hours from the freeze cycle.

[peggy w]

that is a cool idea. I wish I had more room in my freezer for something like that. Right now I pre freeze stuff on cookie sheets. I get the next load ready when I start a load in the freeze drier. That way they are frozen thru and ready to go in the freeze drier. This is hard on my cookie sheets, they want to rust, but until I find something better that is what I use. 

[Christopher N.]

I have been wondering if anyone is able to share their experience with changing the oil in their HR FD vacuum pump.  Mine is the JB Industries Eliminator DV-6E model.  I just did my first oil change today after having run through 10 FD cycles.  A picture I've tried to include shows what my used oil looked like.  file:///Users/christopher/Desktop/used%20FD%20oil.jpg  Based on the brown color of the oil, I think I will change it more frequently.  I tried draining about 1/8 cup after each FD cycle and replacing it with fresh oil, but only did it for the first 5 cycles as I couldn't see any evidence of water in the oil.

 

When the pump was still warm I drained the oil from the bottom into a little pan.  With the FD drain tube valve open to air, I placed a paper towel over the vacuum pump exhaust and covered it tightly.  I then turned on the vacuum pump by plugging it directly into an outlet for about 40 seconds (against my better judgement, as I always thought you shouldn't run any motor without oil in it).  It did, however, evacuate about an additional 1/3 cup of oil.  After I turned it off again, I then tilted the pump forward up on the end with the glass window for about a minute or so, then back flat again.  I repeated this tilt one more time.  Only a little more oil came out after doing that twice.  I closed the drain valve and refilled the pump with a little more than 3/4 of a quart (almost 800 ml) of clean oil.

 

After having read the two instruction manuals that came with the pump I should have probably considered flushing the pump (pouring 1/3 - 1/2 cup oil into the pump as it is running) as it directs if the oil is badly contaminated.  I think I will do that for the next oil change. I suppose this is to be done with the drain valve open??  It says to repeat as required until contamination is removed, then dispose of that oil.  

 

I know that the vacuum pump is one of the most important parts of the FD system.  I want to make sure I'm taking care of it properly.  Has anyone had experience with removing the pump cover, the oil deflector, and the cover seal for a deeper cleaning of the inside of the pump?

 

I'd appreciate hearing from anyone about their oil changing experiences.

[peggy w]

Christopher

I had to flush my vacuum pump and found that it took more than the 1/2 cup it calls for in the manual. I used almost a qt of oil before it really cleared up. Not sure if my oil was extra dirty or what. I think if you want to take out a little and add a little each time, you almost have to open the intake valve and run the pump while doing it. Otherwise, the only oil that comes out is what is in the front by the window. The water and dirty stuff is back in the chamber. I don't know if I am right about this but that was my experience.

[Christopher N.]

peggy w, thank you for your input.  I sure am curious now about "removing the water" from the oil between FD cycles.  Section 9 - Troubleshooting (in supplied HR owners manual) says to drain about a tablespoon of used oil before beginning a new batch of food in order to drain any water that has accumulated in the vacuum pump.  It is my understanding that water would sink to the bottom, as oil floats on water,  but does that mean it sinks down to the drain valve or perhaps in a back chamber??  If it is indeed the case that I would need to run the pump to flush out a bit of oil due to the water and dirt being back in the chamber, as you suggest, I'm afraid I'd blow out more oil than intended and would just be better off not doing that between each cycle, but rather change all the oil more frequently.  Perhaps every 5-8 cycles instead??  I'd love to hear from others as well regarding their oil changing experiences.  Thanks again, peggy w.

[finishman2000]

I find there are factors that come into play that decide the amount of water in the oil. 4 trays of a dry cheddar cheese will let you extend the cycles between oil changes, trays full of apples or onions will shorten it. I always  drain more than a table spoon between cycles and sometimes drain some out to lower the level while in the middle of the cycle to maintain the proper level. I have yet to have any oil come out of the vent. 

I do wish there was a way to have another chamber that traps the water before it gets to the pump. I think I could use a small compressor dryer but the cost of running it would more than likely be greater than the cost of the oil change. I'm waiting on my kill-a-watt meter to come in and actually see how many amps I'm pulling. I have a small dryer that I can try and see what my total amps would be and if it made a difference. 

[Kerry Beal]

Did some more raspberries - the dregs of a bag of frozen - there might be a few whole berries in there but the rest will be powdered.  

 

 

Black Cherry yogurt.

 

 

Spiralized zucchini and swede - gotta say the turnip is darn tasty.  

 

 

There was also a tray with meatloaf and ragu - it would appear I forgot to take a picture.  

[Erika]

Hello finishman 2000, your apples look beautiful... Do you by any chance remember how long did the freezing/drying/cooling process took?.... I haven't been able to get a complete cycle with cero problems.... I am doing my first batches though... My drying cycle runs on 7 hours every time and time doesn't seem to go down. Any comment would help tremendously.

[Cowboyartist]

Erika,   I just completed a load of pears, four trays.   The freeze/drying time was right at 34 hrs, a lot of moisture in the pears.  I also had not flushed the pump after 23 runs.  I had changed the oil twice and added oil several times as I drained out moisture.  I think that the oil was getting a little old, it was really dark and dirty.  

 

As apples go, I have run about 50 lbs of apples and have found that the default settings are ok,  9 hrs freeze time and 7 hrs drying time.   I have also pre froze the apples and was able to cut freeze time to 7 hrs.  Good luck

[Christopher N.]

finishman2000, thanks for your input as well regarding the oil changes.  I find it easy to believe that less moisture will enter the pump when one starts with less moist foods.  I'm afraid, however, that most of the foods I will FD will be quite wet to start with.  I am not sure I understand the compressor dryer concept, but I did find (on line search) some in-line, general purpose filters that remove harmful water condensate and dirt from compressed air systems.  A single stage ($50) up to many stage systems ($600) are available, but I think that might be overkill and I would just be better off changing the oil more frequently.  I totally agree, however, that it would sure be nice to have a chamber or filter, pre-pump that could collect the pump damaging moisture, perhaps even installed by HR.  Thanks again, and let us know if you find any solutions.

 

FYI... If anyone tries FD'ing peeled garlic, I highly suggest either slicing or chopping it first, as the whole peeled cloves took 3 cycles and still, not all were fully done.

[finishman2000]

if you guys are running over 30 hours........and it is stays in the second stage (heating and cooling) you may want to deice in the middle od the second cycle. I have found that when the chamber gets too much ice it really really extends the overall time.

If I find that I'm still in the second stage after 7 or 8 hours (if I'm home and catch it) I'll turn the unit off, put the trays in my freezer (you will see that they well on their way to being dried out), use a heat gun and quickly get the ice out. I have it down to about 10 minutes. I the dry it way a cloth and get everything back in and turn it on again. I have been resetting the freeze time (stage one) to an hour to an hour and half. and walk away. So far, the unit goes to the third stage very quickly (I haven't been watching to see when it goes) and in 7 hours everything is done.

 

This just what I'm doing...I have no idea if it's right or wrong but seems to be working for me. These units will only handle so much water. I wish they showed the internal temp on the chamber, I bet that would tell us a lot about what is going on inside. 

[finishman2000]

Christopher, I did talk to HR about doing something to save the pump but they said they could not find away to do it without raising the cost too much which I agreed. $4k was at the top end of my limit. $5k and I would have passed. I'll be sure to post if I try something to filter out the water.

[Cowboyartist]

fisherman 2000       I found a IR Laser Thermometer on e-bay for around $ 20.   I have been able to measure the chamber temp down to -58 degrees.  This was a the end for the freeze cycle.