Thursday, January 12, 2012

Making astronaut ice cream in my home shop



In his recent post, Chris Gammell used astronaut ice cream as a fun example of how high tech innovation trickles down to consumer-level products. Seeing an image of astronaut ice cream in my G+ feed got me thinking about making some of my own. I managed to accomplish this with a harbor freight vacuum pump, some dry ice and various hoses and fittings. The process is known as freeze-drying and allows water to pass directly from ice to vapor, thus allowing the ice cream to maintain its physical structure while it is dried.

What should I freeze-dry next?

http://engineerblogs.org/2012/01/weekend-journal-the-trickle-down-techonomy/

21 comments:

Adam said...

Ben,
Fantastic videos, as always. Thank you for producing them!
You should freeze-dry pineapple. Trader Joe's carries a really interesting "vacuum fried" pineapple product that I gather is popular/common in southeast Asia. They're sort of sweet and very crunchy, almost like (not at all salty) pineapple chips. I wonder if you could get a similar effect with freeze-dried "astronaut" pineapple. Give the stuff at TJ's a try so you see what I'm talking about, and thanks again for the videos!
-Adam

Tom Hargrave said...

I wonder how freeze drying your own coffee would work out?

Jonathan said...

I seem to remember that strawberries or other berries in breakfast cereal are freeze dried to preserve their delicate structure, that could be interesting to reproduce :)

Anonymous said...

I don't understand how long did you do the -30 cooling and heating? In the video you showed taking the flask out of the water cooler. But how long did you take it out and how often.

Ben Krasnow said...

Anonymous, I left the ice cream at -30*C for about an hour at atmospheric pressure in the water cooler. I then applied vacuum while still holding the temperature at -30*C. After a good vacuum level had been reached, I took the ice cream out of the ethanol bath and applied heat with the tungsten lamps. This lasted about 18 hours.

Ben Krasnow said...

Adam, thanks for the idea. Vacuum frying (as a I just researched) is basically a deep fryer inside a vacuum chamber. This causes the boiling point of water to be lower and so lower oil temperatures can be used. Conversely, pressure can be applied to a fryer to raise the boiling point of water. Apparently this is how KFC cooks their chicken. I am definitely going to look into this. -Ben

5cc7f8fa-3fe8-11e1-8a90-000bcdcb8a73 said...

How much would you say your entire apparatus cost to make? Any hints on where to get bargains on flasks, pump, etc.?

Ben Krasnow said...

5cc7f8fa..., The pump cost $175 new from Harbor Freight. You could probably find a suitable vacuum pump for less. Harbor Freight has a smaller model that will also work for $125. You could also try eBay, or craigslist. You don't really need the water cooler -- you could achieve the same thing with alcohol ($15) and dry ice ($15). The tubing and fittings came from mcmaster.com ($30). The flask and stopper came from LabPro ($10), but any lab supply place will have them. You'll need to find/built a cold trap perhaps from a vacuum flask ($20) and copper pipe ($20). My design is not that good, so your cold trap should have a larger interior volume, and I am going to redesign mine very soon. The vacuum gauge came from eBay, I forget what it cost. Good luck!

Matt Hall said...

Can I ask, why is the heat trap actually needed? It seems that once the moisture has left the food, one needn't bother with it. Would the moisture damage the vacuum pump, or is there another reason?

Cheers,
Matt

Ben Krasnow said...

Matt, the trap is a "cold trap". It freezes the water vapor that has been extracted from the ice cream. Without it, the water vapor would pass into the vacuum pump, and a lot of it would condense into liquid water inside the pump. This would cause rust and failure over time, but the water may also build up so quickly that the pump would fail simple from being overfilled with water!

Anonymous said...

Hi Ben, my name is Tomas and I dont have an ac here, but let me tell you that I love what you do here. I watch your videos.
About this I can give you an idea. I am from Prague, Czech Republic and we had this major flood back in 2002. And that time a lot of libraries were flooded. I remember they used this technique to dry them out without damaging the books. I remember they put all of it into the freezers and doing this procedure. You know all those historical books from whatever century. You may try this. Good luck!

Anonymous said...

Hi,
plz can you write for me what was Mr Ben saying in the videos (with details) because i don't understand while listening, My english is bad
I'm intersted by the subject and i would like to now details. with text i can understand the subject well.
Thank you for your help :)

Keith Anderson said...

What about a giant canister of silica gel kitty litter as your moisture trap? Use it, then bake it to drive out the moisture, use it again. If you are paranoid, put your cold trap between the kitty litter and the pump just in case....

Anonymous said...

Does anyone know what kind of hose that is? I am trying to replicate the experiment...

Ben Krasnow said...

Anonymous, it's vacuum hose from McMaster, part number 5393K45

Anonymous said...

JuJu said:
While looking for a unique snack to send a college freshman, I became convinced that someone needs to make freeze dried picklechips from bread and butter sandwich slices. I even sent a suggestion to a NC based company that sells jars of the standard burger toppers nationwide. Would you be willing to attempt these? I have seen fd jalapeno rings marketed to the spicy snack seekers and really wish to see some puckermakers treated the same way!
:)

I am a fan of astro-ice cream as well!

Anonymous said...

Freeze dried "Floral Gel" aka "Water Beads" aka "Xploderz ammo", superabsorbent polymers. Would these maintain their inflated structure or just collapse into a powder?

(But please, try the previous poster's bread and butter chips first, I'd love to see those on the market!)

superUnknown said...

Nice Snap-On electronic screw driver!

Anonymous said...

Hi, does the water vapor damage the vacuum pump?

Arobertsbu@gmail.com said...

Ben, I thought it was interesting that you left the vaccuum pump on for as long as you did. Was this simply to maintain the vacuum strength or do you think it was moving very much air? It seems to me that once a certain level of vacuum was attained, the pump would not do much more than pump out random particles and leaking air. Maybe a circulation fan would be more effective once the atmosphere is drawn out? The fan might also help you to manage the ice distribution.
What do you think?

Ben Krasnow said...

Arobertsbu, most vacuum systems are pumped continuously. Many materials outgas and will slowly raise the pressure level unless a vaccum pump is constantly running to remove the outgassed material. In this case, the water itself will be sublimating, and raising the pressure to the point where it would not longer sublimate unless pumped.

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