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I've got in mind to make a dish with compressed watermelon, but I don't have access to a vacuum machine. I've tried once using weight, but it just cracks because the pressure is all from one side. Thoughts? If not, can it be done with a home vacuum food-saver type device instead of a restaurant quality vacuum machine? What about denser foods such as canteloupe or cucumber?

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Can you expand the question to see if a home vacuum machine is sufficient or if you really need a chamber vacuum? I've been wondering the same thing and was about to ask the same question. –  yossarian Aug 17 '10 at 3:29
    
I'd also be interested in the more general case. I've had compressed cucumbers which were also really nice. –  yossarian Aug 17 '10 at 3:32
    
I've made the question more general for both of yossarian's comments. –  Michael at Herbivoracious Aug 17 '10 at 5:44
    
Thanks! I sure hope my answer below is wrong. I also added the sous-vide tag, since that's how Thomas Keller categorizes these dishes. –  yossarian Aug 17 '10 at 13:35

5 Answers 5

up vote 5 down vote accepted

Haven't tried it but here: http://newmountaincookery.typepad.com/a_new_mountain_cookery/2008/06/compressed-wate.html

The link suggests the following technique:

  1. Vacuum seal pieces of watermelon (if you don't have one, just put it in a ziploc bag and take out as much as the air as possible)

  2. Freeze it overnight

  3. Take it out and thaw

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Good tip! I'll wait and see if there are any other equally brilliant suggestions but this could easily be the best answer, and I bet it would work just as well with cucumber etc. –  Michael at Herbivoracious Aug 17 '10 at 5:47
    
@Michael - It was amusing synchronicity since I was going through my things_to_try tags on delicious and ran across the mtncookery tip and your question at almost the same time. I'll also have to give it a shot since it's prime Hermiston watermelon season here in Oregon. –  wdypdx22 Aug 17 '10 at 18:48
    
So this totally worked, at least with cucumber. It came out of the freezer limp but not mushy in any way, very much like the compressed melon I've had at restaurants. You can slice it thin and it is translucent, and you can practically wring water out of it. And it is flexible. Very, very cool. Thank you! –  Michael at Herbivoracious Sep 9 '10 at 3:53
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I know this is an old answer, but any chance you could take a few minutes to summarize the main points in your link? Links aren't all that helpful without context, and if that blog ever dies, then this answer dies with it. –  Aaronut Feb 5 '11 at 23:35
    
FWIW, freezing vs compression does yield different results and textures. Freezing breaks cell walls and has a "mushier" result. Compression removes air spaces between walls. Also, it's possible to combine compression with flavors that you can't do as well with this freezing technique. The compression actually pushes flavored liquid in the air gaps between cell walls - for example compressed pineapple spears with Malibu rum taste like Pina Colada Bites. –  Adisak Mar 7 '11 at 5:05

This technique described in the link below works well with watermelon.

http://www.cookingissues.com/2013/08/03/new-technique-pressure-pickle-and-the-cucumber-martini/

You need a ISI whipper, but that is a heck of a lot less expensive than a chamber vac.

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Both the chamber and simple vacuum sealer produces the same pressure once the process is complete. That would be 15 pounds per square inch. The chamber process has an extra step, and it's important. When the vacuum is being drawn in the chamber, the food is exposed directly to the vacuum, and air from inside the food is free to diffuse out. You can see this as the "boiling" effect in the videos. Then, when the seal is made and the chamber is purged, the food is compressed. This is much more effective because liquid can get forced into the the part of the food that used to contain air. With a simple sealer, the plastic bag gets forced against the food right away, and this prevents air from diffusing out of the food.

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"The chamber sealer gets around this by creating the same vacuum on both sides of the bag."

If you have a vacuum, ie the same pressure on either side of the bag then there is no force on the contents of the bag.

To quote Thomas, "Place the piece of watermelon in a bag and vacuum-pack at the highest setting."

The pressure on the watermelon comes from the atmosphere pushing equally on all surfaces of the bag, trying to make it smaller. This is why weights won't work, they only puch on two sides of the watermelon.

A

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I've wanted to do this at home for some time, but am concerned that nothing but a vacuum chamber will really work. Thomas Keller in Under Pressure says "Compression, which requires a great deal of pressure..." Additionally, my understanding was that compression does not rupture the cell walls, but rather evacuates the space between the cells making a dense, crisp texture with an enhanced flavor (same amount of flavor in less space). That is certainly how it's described by Mark Hopper of Bouchon Las Vegas who is credited with coming up with the technique. I would think that methods that didn't use a vacuum (weight, freezing) would tend to rupture the cell walls rather than just pull the cells in to a more dense packing.

My guess is that a home vacuum sealer is not strong enough to create the vacuum necessary, but I've never tested it. The Thomas Keller quote and the lack of this technique on popular sous vide at home blogs makes me a little skeptical that it's feasible with the cheaper home models. Sous Vide Cooking lists two issues with the home style vacuum machines, liquid extracted from the fruit can clog the machine and the vacuum isn't strong enough.

A little further reading shows a more fundamental issue with a home vacuum sealer. Reading the sous vide thread over at egullet, I found a post from dougal that gets at the more fundamental difference between a chamber and home vacuum sealer.

A bag has almost no rigidity - if there's a pressure difference between one side of the plastic film and the other side, the film will just flex and stretch to relieve the pressure difference. The only way a pressure difference between inside and outside the containment can exist is if the containment can resist the force resulting from the pressure difference. A bag simply can't. However, a "rigid" container can. Inside a flexy bag, the pressure is going to end up at atmospheric - regardless of the pump.

So the more fundamental issue with a home sealer is the pressure outside the bag rather than in. A home sealer with a bag (rather than cannister), can expel air but not create a strong vacuum. The chamber sealer gets around this by creating the same vacuum on both sides of the bag.

I sure hope I'm wrong though, because i'd love to make Thomas Keller's Steak Tartar with Egg Yolk (aka Watermelon with Mango).

I swear it's fruit

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As the cell walls are rigid, I wouldn't think there is any way to compress them together without rupturing at least some of them. –  kevins Aug 17 '10 at 13:39
    
@Kevin, I really don't know. None of the sources I can find talk about the cell walls rupturing, they all just discuss evacuating the air between cells. That's how it's explained by Mark Hopper, the chef credited with coming up with the idea to vacuum compress fruit: starchefs.com/events/studio/techniques/Mark_Hopper/index.shtml –  yossarian Aug 17 '10 at 14:54
    
Very helpful answer! I was conflicted as to whether to give the star to this one or the freezing technique. I opted for freezing just because I'm an optimist so I chose the answer that said I had hope :). –  Michael at Herbivoracious Aug 18 '10 at 2:52
    
@michael, obvious answer is: try first, stars later. ;o) –  yossarian Aug 18 '10 at 3:34
    
Indeed, I'll change the star if I try it and it doesn't work. –  Michael at Herbivoracious Aug 18 '10 at 22:01

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