Freeze Dryers and Freeze Dried Food (Part 2)

[Pipsqueak]

[Deryn]

Ick but thanks, Pipsqueak. Makes me wonder why they don't design these pumps to have a drain at all low points. And/or maybe what is needed too is some kind of injection/pressure wash out system one could hook up every few uses to get the grunge off the sides and propel it down to a drain. But .. failing all that .. my ad for the cabana/oil changing boy will stand.

Edited March 26, 2015 by Deryn (log)

[Pipsqueak]

I wouldn't expect yours to be as bad as mine, I abuse it a little.  I haven't been keeping track of how often the oil needs changed.  

 

I've been drying fruit that is really thick - apples almost an inch.  I pre-freeze everything in my chest freezer, and chill the freeze dryer for about an hour before I put the food in, and then let it cool for about 2 hours after I put the food in.  A lot of cycles I get almost a gallon of water out.  The really heavy loads I've been running 16 hours on the final dry cycle.  I use a hair dryer to defrost, so a lot of the loads the vacuum pump is only off about 4 hours between cycles, and then running for over 24 hours.  I should probably change the oil every 5 cycles or so.

 

It looks like if you let the used oil set for a month the nasty stuff all settles to the bottom, and the oil on top looks pretty clear.  You could probably dump it back in.  I plan to filter mine and use it again.  I'll probably start changing it more often.

[Rett]

Is there any other cause possibly for oil to be blown everywhere other than the valve not being closed?

[Gypsyman]

A vacuum leak at the door seal, loose vacuum line fitting or an overfilled pump could all cause oil loss out the exhaust.

 

As for the water vapor contamination of the pump oil. I will be installing a frontline vapor trap ahead of the pump to help with that issue. I think part of the problem is that Harvest Right now uses the cheaper Eliminator pump which doesn't have a gas ballast valve to help eliminate part of the water vapor during initial pull down. Long term I plan on upgrading the pump to the Platinum which has a gas ballast and using the vapor trap ahead of it.

[TonyC]

Tony - By any chance have you repeated your temperature test at all? The more I look at your chart the more I am confused by what appears to be happening temperature wise.

 

As I noted I was told that the temperature would cycle up and down for many hours between -50F and -5F and it was not till the drying was done that it would begin to rise to +50F. Secondly, I see your chart seems to be only for a 12 hour period - what food did you have in the drier on that run that it would dry that fast?

 

When I spoke to my contact at HR a while back he said that I should not expect my runs to be less than about 20-24 hours (though I had success at 16 hours on my first run (from start of freeze cycle to removal of food).

 

Deryn,

 

I ran the test twice with very similar results. The first test I placed the sensor on top half way back.  The 2nd test I placed the sensor upright between the trays and the door plug (not on a shelf). 

 

I may have inadvertantly confused you because this is not the entire cycle.  The table shows the freezing (phase 1, 9PM- 7AM) and only the first two hours of the cooling / drying cycles (phase 2).  I then went to bed.  At the end of phase 3 the temps were ~60F and at the end of 20 minute cooling cycle they were just below freezing.

 

I ran the phase 1 cycle long enough to see just how cold the compressor would get the freeze dryer.  When it leveled out for 2 hours at -39F I started in on Phase 2 at 7AM.  The temperature changes from 7am to 9:09 am are quite dramatic.  I believe that even though the "air temps are high, the chamber walls are well below freezing all the time (I surmise... I have not measured them, but ice buildup makes a compelling case that this is so).

 

I hope this clarifies what I measured.  I should have explained the chart better.

 

I 'll try to run the test from beginning to end with high density readings early on where temp fluctuations are greatest and then fall back to hourly measurements

 

Freezing - Phase 1 - Hourly readings

Dry/Cooling cycle - Phase 2 - High density readings the first two hours, then hourly

Post Drying cycle - Phase 3 - Hourly until completed

Cooldown - Phase 4 - Temp at Beginning of cooldown and at Beep

 

I did not expect to see temps above freezing...  but quite frankly I don't care... the system works very well, and the final freeze dried product is excellent... and we are "pleased as punch" with our freeze dryer.

 

These Harvest Right engineers are quite clever.  There are several ways to control what's going on within the chamber and they took the simplest most cost effective method to do it with the least wear and tear on components, and on your electrical bill. I am sure there have been many incremental changes from the first design to what we see today.   

 

As an aside,  Our Freeze Dryer cycles between 500mT and 620mT.

 

I have had food complete in under 20 hours.  We have since started double loading 1/4" - 5/16" thick banana and apple slices on the trays stacking them like shingles.  We pre-freeze everything first and typically set the dry time to 12 hours.  It normally take 30 - 34 hours using this technique.  We've never had too much icing either.  It's been almost an 1' thick on the sides, but no where close to that on the top or bottom.

 

Corrected a few errors... I am sorry to have been away so long after posting that chart. Didn't mean to cause any confusion and I could have further explained things sooner.  I used an inexpensive Acu-Rite Indoor Outdoor thermometer Model Number 00606tx.  The transmitter is 5"L x 1.5" wide x .75" thick.

 

 

I measured twice - the first time above the top of the trays on the white corrogated plastic.  The second time it was placed upright between the black plug and the tray frame seated on the bottom of the chamber cylinder.

[TonyC]

rock it all you want, it won't get the rust off the inside pump cartridge.....and there is rust.

 

I agree.

 

I have taken my pump cover off both times that I have changed the oil.  I change on the 8th cycle.  On cycles 1-7 I drain out the water and top off the oil level.  Just an ounce or so.

 

When I took the cover off the first time the rust was flaking off the top steel plate.  I removed it and scrapped / cleaned it up, then reinstalled it.

 

Water vapor condensates on the top of the cover and then drips onto this plate where it sits, jells with the oil, and starts reacting with the steel plate creating quite a lot of rust.

 

This morning I changed the oil for the second time and replaced the rusted steel plate with an aluminum one that I made. 

 

Aluminum will oxidize as well and when it does it will show as a white powder.  The plexi glass should hold up to the water and the oil, but the temperature may be a problem.  The flash point of Robinaire pump oil is 420F, the melt point for plexi glass is 275F.  I know the pump reaches about 120F, but I need to test to see just how hot the oil becomes before I go with the plexi glass option.  I'll be measuring the oil temps in the next few days to see just how hot the oil becomes.  If it is well below 200F the plexi glass will go in next oil change (if I see aluminum oxide on the new plate).    

 

The pump housing is showing rust as well, but not as badly as the plate.

 

If you look at the picture below you can see the original part on the right after being scraped and thoroughly cleaned, and the two replacement parts that I made.  The middle one is all aluminum, the one on the left is aluminum angle with 1/4" plexi glass. 

 

The pump has 3 months use on it. 

 

I suspect a lot of the orange brown gunk in the bottom of my used oil jug is simply desolved rust.  I am going to find out just how much as I am dropping a magnet into the oil jug and will see how much iron oxide accumulates around it.

 

[TonyC]

One other warning about placement of the vacuum pump in relation to the freeze dryer.  I had my pump within 6" of the freeze dryer on a counter.  It worked there fine through the cold winter months, but as spring came and my garage reached 70F-80F I noticed that my FD cycles were taking longer and that the condenser of the Freeze Dryer was much warmer. Even after extending the post Drying Time by 5 - 6 hours I would still not see the XXX that indicates < 10mTor,  that had been normal.

 

I moved the pump below the counter to isolate the pump heat away from the Freeze Dryer intake. My cycles times and mTor reading are back to normal.  I think the vacuum line should exit the left side of the Freeze Dryer.  This would allow the condenser fan exhaust to cool the vacuum pump the same way it cools the compressor.  I know the exhaust air is roughly 100F-105F as it is slightly warm to the hand, but the pump is quite a bit hotter then that, and moving air helps to dissapate heat.

 

I also had a few water drips coming from the front of the unit - usually during defrost.  I traced them to the inside front of the chamber where the insulation stops/thins near the front panel.  I also noted that the circuit board was mounted at an angle and the water drops were in direct line of where the board would be if it were mounted flush (right where a mounting hole is located for flush mount of the control board). I suspect the board was relocated slightly to avoid the possibility of these drips.

 

I cured this problem by placing 1/2" thick x 1/2" wide x 18" long strip of stiff closed cell foam between the front panel and the insulation on the bottom half of the chamber.... It easily went in place.  No condensation collecting on the outside of the chamber means no more drips!  Worked like a charm.

Edited April 16, 2015 by TonyC (log)

[TonyC]

I am not sure if anyone has done this yet but we prefer our eggs to be freeze dried raw and then vacuum packed in jars. We can make great omelets or use the eggs in recipes this way every easily.  We located 4 small 11" x 7" x 1.5" deep pans to freeze our raws eggs in (15-18 eggs at a time depending on the size), then we transfer them over to the FD pans.  This makes the task easier.

 

Here is what we do:

 

1) We line the pans with parchment paper and pour the scrambled egg mix in and freeze. The 1 1/2" deep pans keep you from spilling them on the way to the freezer, and are just the right size to fit the FD trays..

 

2) Once frozen we transfer the contents over to the freeze dryer trays.  No need to add addtional parchment paper.  1 2/3 pans will fit per FD tray.  The eggs cut easily with a knife.  Here is a picture of the eggs removed and placed in the FD tray ready to go into the freeze dryer

 

3) Once out of the Freeze Dryer, we place the eggs into a zip lock bag and use a roll pin to break them up into crystals.  You can mash the zip lock bags with your hands just as easily. 

 

4) We then pour the contents into our canning jars and vacuum pack them. 

 

 

This Freeze Dry batch consisted of a quart jar of 18 eggs( Left Jar) , 3 pint jars of cooked lima beans with ham (front right), 2 jars of apple slices, and a jar of banana slices.

 

We pull a miminum 29.5" vacuum on the jars.

 

The pans that we used are "Wilton Recipe Right 11 Inch x 7 Inch Biscuit Brownie Pan" from Amazon for $4.99 each

Edited April 16, 2015 by TonyC (log)

[Deryn]

 

 

The pans that we used are "Wilton Recipe Right 11 Inch x 7 Inch Biscuit Brownie Pan" from Amazon for $4.99 each

 

 

Almost double the price here in Canada - but thanks for the specs. I will get some of those.

 

Thanks everyone for all these very helpful posts today. Tony .. we missed you. Thanks for answering my query - yes, I was confused but as everyone has said, despite the confusion sometimes, the machine works very well. I just wish I was as 'handy' as some of you are at figuring out pump issues and solutions, etc. But, please keep the posts coming as you discover new things because someday I will find someone to help me try out some of your innovative ideas.

[TonyC]

Almost double the price here in Canada - but thanks for the specs. I will get some of those.

 

Thanks everyone for all these very helpful posts today. Tony .. we missed you. Thanks for answering my query - yes, I was confused but as everyone has said, despite the confusion sometimes, the machine works very well. I just wish I was as 'handy' as some of you are at figuring out pump issues and solutions, etc. But, please keep the posts coming as you discover new things because someday I will find someone to help me try out some of your innovative ideas.

 

Hi Deryn,

 

Re: almost double the price

I purchase from both Amazon.com and Amazon.ca all the time.  I check prices, shipping, and exchange rates... and purchase from the lowest.  The Logon info is the same at both web sites.

 

Re: Cleaning the vacuum pump

All you need to get into the pump is a set of allen wrenches.  You'll need the 3/16 one (a SAE set can be purchased for 6.99 from harborfreight.com, item number 69369).  For our purposes these are just fine.

 

There are 6 allen screws around the front cover.  Drain the pump oil ( open the valve and let it drain completely...even when you think it is finished dripping let it sit another 30 minutes or so )

 

I use disposible nitrile gloves ( $7.99 at harborfreight.com item number 68496 - 50 pair) to keep the oil at bay.  Just pull the cover off and wipe the inside down with an old cotton rag.  Do the same for the areas that appear to be grubby on the inside of the pump.  I used a small putty knife to get all the loose rust and oil off the top plate. (if you remove your filler cap and look into the hole, the metal you see is the plate that rusted up on my pump. Remember that there is nothing loose under the cover, so you can't hurt anything.  

 

Once everything is cleaned up check to see that the rubber gasket seal on the pump housing is still in its channel - mine tends to fall out of the channel at the bottom.  I simply place it back in the channel and reinstall the cover.  Tighten the allen bolts as tight as you can using the T handle allen wrench and you're good to go.

 

Takes about 15-20 minutes to complete the entire task.

 

The next time that I'm in there I'll post a simple procedure with pictures if you are still hesitant to attempt this. 

 

BTW, the plate that I replaced was held in place with the same 3/16 allen bolt as those holding the cover in place.

 

One final thought. harborfreight has 20% off coupons around almost continuously (searh the coupon sites on the web), and you may have a store local to your area.

 

Have fun!

 

Tony

[Deryn]

Thanks, Tony.

 

I have masses of tools. Pretty sure I have those wrenches, etc. Just haven't braved it yet. But, I would very much appreciate a step by step with pics if/when you get around to posting them.

[Rett]

Is it normal for the fruit to soften up after being opened? It comes out of the freezer drier crunchy and was bagged right away in Mylar bags with an oxygenator. When we open the bag the strawberries they aren't really crunchy and they soften up as time goes by. They taste fine but I want to Make sure they are ok to feed my family. I also did green scallions which felt completely dried after the cycle but have softened up in the mason jar which also had an oxygenator in it. Am I doing something wrong? I hate to think all my previous cycles were stored wrong. I stored a lot of raw beef patties and precooked meatballs too. I will check those and see if they are still dry.

[TonyC]

This is the easiest way that I have found to vacuum pack Mylar bags.  I think I'm going to stick with it.

1. Using an Ice Pick puncture one side of the bag 1/2" from the top corner.  I poke through from the inside out to insure that I don't damage the other side of the bag.  This picture shows the location of the hole.  It insures no waste to the bag.
   
   
    
2. Next Insert product and O2 packet and seal the entire edge of the bag between the outer edge and just beyond the hole placed in the corner of the bag.
   
   
    
3. Insert the trusty suction tube into the bag.  Whatever tube you use needs to be stiff and long enough to get deep into the bag close to the product, otherwise you will seal off a small portion of the bag and leave a lot of air inside.  I push the tube near to the product.   Further down I go into detail on how I made my suction tube.
   
   
    
4. Position the corner of the bag with the hole across the impulse sealer.  Turn on the pump and slowly remove the tube from the bag as the bag is sucked down round the product.
   
   
    
5. As you approach the hole with the end of the suction tube, place your finger over the tube hole and seal the corner of the bag with the impulse sealer.
   
   
    
6. The picture below shows the completed process with a sealed Mylar bag.
   1. Step 1 shows the hole in the bag
   2. Step 2 shows the seal across the entire opening of the bag
   3. Step 3 shows the corner seal isolating the hole ( I actually seal over the hole as well)

 

Hope this helps you.  This is the easiest most inexpensive way that I have found to pull all the air from the bags.   I don't think I even need the O2 packets as I pull 29+" Mg of vacuum.  The above was done with raw steaks and pork a few weeks ago.

Here are the tools I used. 
My home made suction tube.  This is the smallest diameter section of the cheapest available TV antenna that I puchased from Walmart for less than $10.  To disassemble the antenna, extend it, Snap off the largest end of the antenna at the bottom with a pair of plyers ( don't cut it, snap it off - it separates easily), cut the ball off the smallest end, and push all the sections out the big end that you removed earlier.  This will leave you with 5 or 6 sections each about 1 foot long.  I use the smallest diameter size.
 

The Ice pick

 

The 5MM wide 12" long Impulse sealer



The $79 HF 2.5 CFM Single Stage Vacuum Pump.  Any vacuum pump will do, but the closer you get to 30" Mg vacuum the longer your food will last.  You pull out moisture as well as O2.   The bags quickly compress around your food.  I found freeze dried pulled pot roast poked holes through the 5mm bags when I pulled a tight vacuum so be careful and insure the food has no sharp ends.  If the food does have sharp edges, it best to use jars to store your food.

 

 

For sealing using canniong jars we use the Food Save Lid Adapters.  They're available from Amazon and other retailers for around $10.  A small clear hose adapter for the adapters sells for around $6.  You'll need it as well.  I pull 29.5" of vacuum using these adapters and each jar is sealed in about 15-20 seconds.  I have opened jars with saltine crackers that were put away without O2 packets 8 years ago and they were as fresh as the day I placed them in the jars.  Just be sure to store them in a cool dark place.  Mine stay between 60F and 72F all year long.

 

 

Any food product with less the 5% water ( all dry goods and staples such as rice, powdered milk, pasta, flour, cereal, pancake mix, etc) store fine this way.  We have even stored candy such as M&M, and Snickers candy bars, as well as scrambled raw eggs  without trouble using this technique.

 

Have fun and good luck freeze drying your food!

 

Tony

Edited April 23, 2015 by TonyC (log)

[Deryn]

Thanks, Tony.

 

Most people who pack foods in mylar for long storage use either suction or an appropriately sized O2 absorber, but definitely not both. If you suction, the O2 absorber is a waste. Mylar will not suck down on its own with just an absorber (since air is comprised of more than just oxygen) but that is not an issue because it is oxygen (and water) that cause storage issues.

 

Among preppers, the predominant method is to use an absorber only.

 

If you have a good mylar bag (and by the way, you should use 7 mil mylar bag in my opinion and it is also good to get the manufacturer/supplier to specify the O2 and H2O penetration stats for their particular bag - not all bags are created the same), it is definitely not necessary to suction out the air if you throw in the absorber. Mountain House certainly doesn't and they vouch that most of their freeze-dried foods last for 20 plus years (and that number is going up every year as they review the state of the bags they packed years ago). In contrast, bags of other manufacturers/suppliers of ready packed freeze-dried foods have been shown to be less able to go that distance - even if they were actually thicker than the bags Mountain House uses (which they have manufactured according to their proprietary specifications).

[TonyC]

Hi Deryn,

 

Thanks for the information.  I have just started using O2 absorbers and I have several questions that I am hoping that you or someone else can answer?

 

• How do you size the O2 absorber for a given bag and its contents?  
• How do you know if the O2 absorbers are still good?  Do they have a shelf life even if unopened?
• What is the best source for mylar bags and O2 absorbers?

Any assistance is appreciated

[Gypsyman]

I've been using discountmylarbags.com for my supplies. Had good luck so far.

 

O2 life is hard to judge but they should not be hard or brittle as they are a powdered product. The packs of them typically have an OxyEye indicator that should be pink if the package of absorbers is good. Once placed in your bag they should get warm to the touch when they begin reacting. Usually takes about 30 minutes.

 

The page below is a good reference for sizing.

 

http://www.sorbentsystems.com/order_O2.html

 

Since you are removing the oxygen (which I believe is about 20% of the volume) you can get a decent "vacuum pack" on product if you just squeeze enough of the excess air out to start with. I have 5 gallon bags of wheat and rice that pulled down as hard as a brick of coffee from the store using just a 2000cc absorber and taking the time to remove as much of the excess air as possible before sealing.

[Deryn]

The Sorbent Systems site is a very good place to do some reading about mylar bags as well. I have ordered most of my bags from them because it has become apparent to me over the years that not all 'mylar' bags are the same at all. One doesn't know exactly the quality of bags purchased from many other sources - though they may be just fine.

 

Suffice it to say that, over time, I have learned that thickness is not the only important criteria when choosing a mylar bag for long term storage (which I deem to be > 10 years). If you are just trying to store your food for shorter than a decade, as long as the bag is a decent thickness and your food has enough H2O removed (as it should have with freeze-drying) and they are food-grade with an appropriately sized O2 absorber and properly sealed, most Mylar bags should be fine however.

 

Gypsyman - thanks for linking to that site. I was about to post a similar SS link about mylar but there is a list on the left of the page you linked to so Tony can explore that whole site from there if he wishes.

[TonyC]

Instant Mashed Sweet Potatoes

The latest Freeze Dryer test was with cooked sweet potatoes.   We baked 7 large sweet potatoes.  When done we used a mixer to create mashed sweet potatoes.  We then placed the mashed sweet potatoes into a single FD tray and freeze dried them.  Once the freeze dried process was completed, we broke up the pieces into 1" sections and used a blender to create a powder.  The powder went into two pint jars.  There are 4 adult servings in each jar.

There are 7 sweet potatoes in the big bowl behind the jars. Each one is bigger then the individual jars.

Add a little water and these are good to go!  We have not tried to reconstitute them yet, but I don't foresee a problem.

 

[harrisgo]

Hi all the foodgeek in the forum    ,

 

My name is Harris from Indonesia. I just bought Harvest right freeze dryer recently and the machine will be shipped it here.  

 

I have questions regarding the electricity consumed by this machine: are any of you have a calculations on how much do you spend on electricity for this machine? (or better how much energy does it consume for a batch of production, lets say.. 8 lbs of banana?

 

My plan is to use this machine to for many kind of food and non-food experiment at home.

 

I will be grateful for any kind of response you guys have. Thanks

 

Cheers,

Harris

[Pipsqueak]

I have questions regarding the electricity consumed by this machine: are any of you have a calculations on how much do you spend on electricity for this machine? (or better how much energy does it consume for a batch of production, lets say.. 8 lbs of banana?

Your electricity usage will be dependent on your ambient temperature where the machine is running, and how big of a batch you are running through the machine.  If you pre-freeze the food, that will save you time and electricity.  If you've read through this forum, you probably have an idea of how the cycle works, so I'll give you some rough numbers on electricity usage.

 

My unit runs approximately:

365 Watts on the refrigeration unit

300 Watts on the vacuum pump

825 Watts on the heaters

 

The first 9 hours of the cycle is cooling only, so 365 W x 9Hr = 3.3KWH.  If I pre-freeze the food to -10F in my chest freezer I pre-chill the unit for an hour, put the food in, let it freeze for another hour, and then kick it into dry cycle.  That will save you about 7 hours.

 

Once the unit kicks into dry cycle, the heaters kick on and off to keep the ice evaporating.  I would say my average electricity usage for a dry cycle is around 1100 watts, but that varies a lot depending on ambient temperature.  The colder your ambient temperature, the more efficient the refrigeration unit runs, and the faster food will dry.  

 

It seems like my average usage per cycle is around 20KWH, but that is an average that can vary widely.  A batch of herbs that only has 8 ounces of water in it can be done very quickly, for probably 7KWH, but when it's really cold in my garage in the winter, I can load 10 pounds of apples in it and run a really long cycle which probably takes more like 30KWH.  (When the ambient temperature is around 40F, I can easily take out a gallon of water in a cycle, I've dried trays of apples sliced an inch thick.)

 

You'll just have to play around with it and see how it works for you.  I was using a Kill-a-watt meter to check the electricity usage of all my cycles, but I had a momentary power failure on one of the cycles, and when the power came back on it blew the internal fuse in the meter.  I replaced the fuse, but haven't hooked the meter back up.

 

So this probably doesn't really answer your question, but hopefully gives you a general idea how it will work out.

[Rett]

Is anyone having trouble with moisture when storing items in mason jars using the food sealer? I did some chopped onions, green onions and chopped celery and they where completely done but after two months in the jars they have softened up. Also did peaches and stored in Mylar bags but when I opened them they had softened up as well. I am not finding any cold spots when I take them out of FD. They seem dried. Any suggestions would be appreciated. I am concerned I will open my bags down the road to find they are not good to eat.

[Gypsyman]

Are you using O2 absorbers?

[Deryn]

You are better off using O2 absorbers than pulling a vacuum. You don't need to do both.

[JimR]

Hi all the foodgeek in the forum    ,

 

My name is Harris from Indonesia. I just bought Harvest right freeze dryer recently and the machine will be shipped it here.  

 

I have questions regarding the electricity consumed by this machine: are any of you have a calculations on how much do you spend on electricity for this machine? (or better how much energy does it consume for a batch of production, lets say.. 8 lbs of banana?

 

My plan is to use this machine to for many kind of food and non-food experiment at home.

 

I will be grateful for any kind of response you guys have. Thanks

 

Cheers,

Harris

I have been tracking electric use for 80 plus FD'ing sessions and my average per session is $1.70 @ $0.12 per kilowatt using a Kill-A-Watt meter. One of the keys is for each session to be 18 to 24 hours. If your sessions are much more than 24 hours you are wasting electricity. The trick is put food with enough water so the machine will cycle properly but not too much water. Having to much water will cause longer, and less effiecent, drying.

 

If you have some high water contend foods just put a few trays of that and one or two trays of food with less water (graded cheese, cooked rice, etc). With practice you will learn how much "high water" food, combined with "med" or "low" water foods to have your sessions below 24 hours.

 

Hope this helps.