Freeze Dryers and Freeze Dried Food (Part 1)

[Kerry Beal]

Ok - so dumb idea back at you.  I thought you could take shell on shrimp - freeze dry - then fry like they do at Lotus of Siam to make the Salt and Pepper Prawns.  

[thegreatdane]

Kerry, what's the company in Utah from whom you bought the unit? I've got to admit, I'm enticed by the idea of being able to freeze dry anything I want.

[Kerry Beal]

Kerry, what's the company in Utah from whom you bought the unit? I've got to admit, I'm enticed by the idea of being able to freeze dry anything I want.

It's called Harvestright - here is a link.  

[Kerry Beal]

Ok - first batch is in!

 

A tray of nice ripe banana slices, a tray of mini ice cream sandwiches, a tray of regular sized neapolitan ice cream sandwiches and a 1 kg container of frozen Boiron mango puree cut into 1/2 inch slices.  I pre cooled the FD'er for about an hour, then dialled it up to 11 hours cooling.  Apparently ice cream sandwiches should be frozen to -40 C until thoroughly frozen through - if their centres are warmer they tend to puff up when the vacuum starts and it makes them ugly.

[Martin Fisher]

I'd love me a freeze drier just for the strawberries! 

[Kerry Beal]

Checked on the FDer this am - still has about 1 1/2 hours on the freezing part of the cycle before the vacuum pump kicks in and the shelf heaters start to do their thing. 

 

A fair amount of condensation on the door of the unit - beginning to understand some pictures that Chocolot sent me showing one of the trays under the door!  Mine now has a stainless Air Canada tray in the same location.  

 

The drying part of the cycle is set for 5 hours - but it will take much longer than that.  What happens is that the pump cycles on and brings the vacuum down to a certain level.  The shelf heaters then cycle on and water starts to sublimate out of the food.  Eventually the pressure rises due to the additional moisture and this causes the heaters to cycle off and the vacuum pump to cycle back on.  The timer resets over and over during the process.  So 5 hours could be anywhere between 12 and 24 hours by the time the microprocessor is satisfied with it's readings (or the water on the condenser overwhelms the unit and you have an endless cycle of melt and freeze on the condenser).  

[rotuts]

Im wondering if you might consider freeze-drying some wine.  one you might drink say ....

 

then use the concentrate as a wine flavoring.   Im wondering if the water and EtHO might be removed but the various flavor

 

components left behind   

 

this should be very very low on your list of experiments.

[gfweb]

Re FD wine...I bet a lot of volatile flavor would go off too.

 

When I lyophilized stuff in the lab (decades ago) , I would always freeze it first with LN2 or dry ice/acetone. This Freeze-Girl (relative of Steam Boy) seems like it takes a long time to get to frozen; why not pre-freeze?

[Kerry Beal]

Thinking that alcohol in the wine is likely to be removed in the process - I would assume that even frozen the boiling point of ETOH is lower than that of water - and I think the sublimation temperature would be as well.

 

Doesn't mean I won't do the experiments though!  

 

Do need to get some dry ice or liquid nitrogen for pre freezing things for sure.  Or maybe an anti griddle?

[rotuts]

""  an anti griddle  ""

 

 

in for a pound .....

 

I had assumed the FD wine would not work.  Id be interesting in wine w the water and EtOH removed, but the 'rest' left.

[gfweb]

Freezing point of EtOH is about -115C. LN2 could freeze it, but the Freeze Girl couldn't hold it there. I believe it would boil off rather than sublimate.

 

The volatiles in wine that contribute to what you smell would have to be lost by the process I think.

[Chocolot]

I love how Kerry gets us all involved:) Off to Salt Lake City I go in search of her treasure. The guys at HarvestRight are really nice. They gave me the tour of the plant. It appears to be very well made and I reported back to Kerry. Next thing I know, the crazy woman has ordered one!! The best part is now I have an "in". I take things down and they dry them for me. So far I have taken leftover ganache-I had visions of it just being poured on a tray, but somehow they managed to made mounds out of it. I tried rehydrating a piece. Not really successful. Next I will turn into a powder and try again. They have done cooked bacon--great for breaking up and putting on my Maple-Bacon piece for an upcoming Cowboy Festival. Fresh sliced peaches are wonderful. I turned them into a coarse powder and will make a peach-almond ganache. They gave me mini ice cream sandwiches that I enrobed in chocolate and returned to them. Very tasty, much like a crisp cookie. They gave me raspberries that I played with. I'll post a pix. I enrobed strawberries. I actually like them better than fresh, but then I am not a fan of strawberries in chocolate.  I want them to do cream cheese--they said it works great. I will turn into a powder and make a cheesecake ganache. About the only thing they said doesn't work is butter. It just melts.

We are lucky to live in a desert. The humidity here is usually under 15%, except today it is 100%. The products will try to rehydrate if left out in the open.  They gave me some pulled pork to play with. I was thinking of doing a pork and bean ganache--don't judge me!!! It was for the Cowboy Festival! I thought the pork might work. I decided against it and just ate the pork in a BBQ sauce. Very nice. I took down leftover peeps. They look the same, but taste like sweet styrofoam. 

I don't now how much longer the guys will FD things for me before expecting me to buy, but I keep taking them chocolate, so it might work for a while.  It will be fun to see what Kerry comes up with.

[Kerry Beal]

Re FD wine...I bet a lot of volatile flavor would go off too.

 

When I lyophilized stuff in the lab (decades ago) , I would always freeze it first with LN2 or dry ice/acetone. This Freeze-Girl (relative of Steam Boy) seems like it takes a long time to get to frozen; why not pre-freeze?

I did pre freeze too - in my upright freezer.  I need to get it cleaned out and defrosted so things can lie flat on the shelf to freeze - especially before I get into stuff like cream and milk. 

[Kerry Beal]

Got home from work last night - Freeze-Girl had 2 hours of drying left - decided to pull everything half an hour before that as I had to work again this am.  

 

Turned off machine, opened the drain hose to allow air back into the unit.  Shelves and product were warm.  

 

The bananas and ice cream bars were completely dry - the mango puree still had dampness at the center.  I bunged that tray back into the deep freeze to put in on my next run to finish it off.  I suspect my 1/2 inch slices were perhaps a little thicker than that!

 

I allowed the unit to defrost overnight - this am there were a couple of litres of water in the drain bucket.

 

Put the various things into vacuum bags with an O2 absorber and heat sealed closed.  

 

 

 

Banana slices - nice and ripe!  Will be excellent as flavouring in a banana filling I think.  

 

 

Mini ice cream bars - think I'll dip a couple of these in some dark chocolate with the addition of 4% butter fat to soften the chocolate a bit.  

 

 

Standard sized neapolitan bars.  Brought a few to work this am - they seem to be popular.

 

 

 

[Smithy]

That looks like a lot of fun, Kerry, and I want one of those ice cream sandwiches after you're dipped them. At some point I hope you'll check the water to see what it's like.

[Kerry Beal]

You mean to see if there is any flavour in it?  I'll give it a sniff tonight before I pitch it.

[Smithy]

Yes, I'm curious about whether some volatiles end up in the water - enough to give it useful flavour. If it's more like distilled water I could imagine using it for watering plants or other household uses in an arid climate, but that hardly applies to your part of the world.

[MelissaH]

I'm definitely talking to you before my next camping trip, Kerry!

[Kerry Beal]

Indeed - I'm picturing decent airline meals!

[Kerry Beal]

Yes, I'm curious about whether some volatiles end up in the water - enough to give it useful flavour. If it's more like distilled water I could imagine using it for watering plants or other household uses in an arid climate, but that hardly applies to your part of the world.

Water was minimally fruity.

[Kerry Beal]

Tonight I'm going to start the next batch. 

 

On the first tray I have the mango puree that was still a bit damp last time - I mentioned I had put it back in the deep freeze to wait for tonight's run.  

 

 

Some shredded cheddar.

 

 

Tomatoes from my garden.

 

 

Liberty greek yogurt with honey - got a couple of those old fashioned ice cube trays with the lever but made from stainless, lined them with parchment.  

 

Also added to the half empty tray are some mini marshmallows.  

 

 

I dipped some pieces of the larger ice cream bars in dark chocolate (with the addition of some butterfat for softness).  

 

 

Lots of shattering happened so made some bark with the remains.  

[Beth Wilson]

I am tempted to take some time off work and head down to your neck of the woods to try some of that bark!  Very hard to not want some delicious chocolate bark for breakfast now

 

What do you use as an oxygen absorber for your vacuum sealed products? 

[Kerry Beal]

You are always welcome!

 

I got 100 oxygen absorbers and mylar bags with the unit.  Uline does carry them too.

[huiray]

I used to do a lot of freeze-drying (lyophilizing) in the lab, but in the format where frozen solutions are externally attached to the manifold or chamber-(platform) leading to the condensating drum.  Typically one used dry-ice/acetone (this was adequate) or liquid nitrogen to rapidly freeze the solution while creating maximal surface area for the sublimation by rotating the flask.  Cooling done to the temperature of the cooling bath.  Solutions of water-soluble peptides, proteins, immunogens, protein-drug conjugates, other water-soluble substances/molecules, that sort of thing.  If organic co-solvent was present one removed most of it first on a rotovap before freezing and lyophilizing.  Vacuum on the freezemobile was not applied until the drum was at least -30ºC.  Vacuum was preferably at less than 100 mT, but "several hundred" mT was adequate.  Ambient heat was sufficient to drive the sublimation; the outside of the vessel would "freeze over" with atmospheric water vapor and insulate the vessel sufficiently so that heat transfer from the surroundings was slow enough to maintain the internal temperature well below the melting point; in fact the temperature of the "ice layer" around the flask would frequently be a fair bit below 0ºC and this ice layer would not melt until the lyophilization was nearing the end and water sublimation was ceasing.  But perhaps folks in MClabs know all this?

 

The freeze-dryer you have is the sort more common in the food industry and in pharmaceutical or medical scenarios - e.g. freeze-drying multiple vials of (aqueous) vaccine, medical formulations, etc - as you well know.  The sort of freeze-dryer used in chemistry and biochemical labs tend to be of the sort I described - like this one or this one - just so folks know there are two basic formats for the process.

Edited September 11, 2014 by huiray (log)

[Kerry Beal]

I have followed a lot of those manifold freeze driers over time on ebay - as well as the chamber ones used for flowers and taxidermy!  Saw one in the place I picked up an old stokes candy pan - wasn't prepared for it at that time!  Nor did I have room in the car (it was in New Jersey).