Sous Vide: Recipes, Techniques & Equipment (Part 4)

[slkinsey]

That wouldn't work, I'm afraid (although there are other tricks you can do with those cannisters).

In a chamber vacuum machine, the air is evacuated from the chamber and the bag is sealed around the food while it is still inside the chamber under low pressure. This is impossible with a FoodSaver.

[derekslager]

Amazon.com recently posted the description from Thomas Keller's forthcoming (October) sous vide book, "Under Pressure". It sounds promising. With the Alinea (October) and Fat Duck (November) books releasing around the same time, we're all sure to be very busy later on this year.

A revolution in cooking. A new era in gastronomy: sous vide is nothing more than cooking food in plastic bags in water at low temperatures--but the results are extraordinary. Sous vide is the culinary innovation that has everyone in the food world talking. In this revolutionary new cookbook, Thomas Keller, America's most respected chef, explains why this foolproof technique, which involves cooking at precise temperatures below simmering, yields results that other culinary methods cannot. The secret to sous vide is in discovering the precise amount of heat required to achieve the most sublime results. Through years of trial and error, Keller and his chefs de cuisine have blazed the trail to perfection--and they show the way in this collection of never-before-published recipes from his landmark restaurants--The French Laundry in Napa Valley and per se in New York. With an introduction by the eminent food-science writer Harold McGee, and artful photography by Deborah Jones, who photographed Keller's best-selling "The French Laundry Cookbook", this book will be a must for every culinary professional and anyone who wants to up the ante and experience food at the highest level.

[Mallet]

That wouldn't work, I'm afraid (although there are other tricks you can do with those cannisters).

In a chamber vacuum machine, the air is evacuated from the chamber and the bag is sealed around the food while it is still inside the chamber under low pressure.  This is impossible with a FoodSaver.

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Not so! Upthread pounce has a really nifty work-around where a check valve is attached to the FoodSaver bag and the whole thing is put inside a canister. Whether it will compress fruit or not I don't know...

[ossified]

That wouldn't work, I'm afraid (although there are other tricks you can do with those cannisters).

In a chamber vacuum machine, the air is evacuated from the chamber and the bag is sealed around the food while it is still inside the chamber under low pressure.  This is impossible with a FoodSaver.

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Damn the physics! Full speed ahead!

[sygyzy]

My FS machines have been tested up over 28hg.

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I recall you saying this before in other posts - that the FS has a very strong vacuum. Whether this is true on a *technical* perspective, it's worthless in action. It simply does not translate to a very strong vacuum. It couldn't even draw bubbles out of a solution.

[Ruth]

On that small point I beg to differ. When vacuuming liquids in a FS canister I have frequently seen bubbles coming to the surface. That said, of course it could be stronger. I am not sure if the strength on all models is the same. I use the Professional III and have to go through all kinds of conniptions to prevent juices from being sucked out of the bags.

[dougal]

I understand that Foodsaver's claim is that their machines can pull to a pressure difference of (about) 24 inches of mercury. (Which seems to be abbreviated, in the USA at least, to "24HG" - Hg being the chemical symbol for Mercury.)

Expressed differently, that means reducing sea level atmospheric pressure by 5/6, ie to 1/6.

"Standard" atmospheric pressure is taken as 760mm of mercury.

1/6 th of that is 126.6 mm.

The temperature at which the vapour pressure of water reaches 127mm of Mercury is just below 57ºC (ie 134ºF) - see http://intro.chem.okstate.edu/1515SP01/Database/VPWater.html

All of which I interpret as meaning that a Foodsaver (rigid) canister could see water boiling at no less than 134F (at sea level).

[sygyzy]

My FS machines have been tested up over 28hg.

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I recall you saying this before in other posts - that the FS has a very strong vacuum. Whether this is true on a *technical* perspective, it's worthless in action. It simply does not translate to a very strong vacuum. It couldn't even draw bubbles out of a solution.

←

On that small point I beg to differ. When vacuuming liquids in a FS canister I have frequently seen bubbles coming to the surface. That said, of course it could be stronger. I am not sure if the strength on all models is the same. I use the Professional III and have to go through all kinds of conniptions to prevent juices from being sucked out of the bags.

←

Would you say it completely clears the solution of air bubbles?

Also, the fact that the FS sucks in moisture from a piece of meat that is wet from brine or marinade does not speak to its vacuum capabilities. I can suck up the liquid with a straw and my mouth and we'd hardly say a human is a strong vacuum.

[pounce]

What's the issue at hand? You can "outgas" liquids with a FS canister and FS vacuum without lowering the "atmosphere" to one that would cause a boil at room temps.

If someone can state a test for the equipment I can run it.

[DocDougherty]

How about a simple case:

3 ft of 1/4" vinyl tubing direct connected through an adapter to a vacuum gage or manometer.

Measure steady state low-side pressure after 1 minute of pump operation.

In my experience it is not so much how good the vacuum pump is, but how much air is trapped in the food by the pressure of the bag. If you are as careful when you set up to use your Seal-a-Meal as you must be when you cast a gold medallion, then all comes out OK. Crushing fruit with atmospheric pressure is perhaps interesting to watch, but once you get the gas out, the remaining water is pretty much incompressible.

Doc

[e_monster]

Would you say it completely clears the solution of air bubbles?

Also, the fact that the FS sucks in moisture from a piece of meat that is wet from brine or marinade does not speak to its vacuum capabilities. I can suck up the liquid with a straw and my mouth and we'd hardly say a human is a strong vacuum.

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I am wondering: what is the relevance of this inquiry?

A FoodSaver does a fine job of vac packing for sous vide cooking, AND it isn't strong enough to compress things like watermelon (though it does compress strawberries nicely).

It also pulls enough of a vac that it does a very nice job of quick marinading/pickling in canisters.

I am not sure what difference it makes whether or not a FoodSaver pulls enough vacuum to pull all the air bubbles out of a solution. There isn't really any question about compressing watermelon: it isn't strong enough to do it. But it is great for most sous vide applications and is MUCH less expensive than machines that pull enough vac to compress watermelon significantly.

(Question: what about putting a weighted plate on top of the bagged watermelon when it is being vac'ed and then leaving the plate on? Note: I am thinking out loud without thinking it through -- so don't flame me if this is an idiotic idea.)

[pounce]

How about a simple case:

3 ft of 1/4" vinyl tubing direct connected through an adapter to a vacuum gage or manometer.

Measure steady state low-side pressure after 1 minute of pump operation.

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Can you state a hypothesis or your expected result of this test?

I'm not sure what it's proving or disproving so I am curious about what this test means to you.

[DocDougherty]

Pounce,

I think it only puts on the table a measurement from a reputable source. Personally I see little practical difference between 1 Torr and 100 Torr. In terms of atmospheric pressure, you are at least 100 Torr lower in NM than I am in SoCal just as a result of the altitude difference but that shouldn't make much difference in terms of the measurement. On the other hand if you have the instrument, it would be interesting to have a sense of how good the dry pumps really are in the commercial Seal-a-Meal type devices.

In the past when I needed a decent vacuum I just salvaged an old refrigerator compressor and attached an upward coiling 3/4" discharge tube to recover the oil that gets pumped out. With a couple of Freon flushes it was good enough to recharge both auto and home air conditioners but never good enough to boil water at room temperature.

Doc

[MikeTMD]

I've been reading the last few posts with a great deal of interest, but how do those ultra-complex matters help us cook better SV food? Are we getting off the cooking track, and into the murky waters of physical chemistry, where most participants involved in the discussion are simply lacking proficiency and competence? In plain English - what's the purpose of all of that?

Edited May 28, 2008 by MikeTMD (log)

[Mikels]

Maybe I can ask a naive question. Once you remove enough air from the FS bag, does it matter if a higher vacuum is used? Does it change the way you cook?

[slkinsey]

That wouldn't work, I'm afraid (although there are other tricks you can do with those cannisters).

In a chamber vacuum machine, the air is evacuated from the chamber and the bag is sealed around the food while it is still inside the chamber under low pressure.  This is impossible with a FoodSaver.

Not so! Upthread pounce has a really nifty work-around where a check valve is attached to the FoodSaver bag and the whole thing is put inside a canister. Whether it will compress fruit or not I don't know...

Oh yea... That's a pretty sweet hack. I wonder if it would work.

I am not sure what difference it makes whether or not a FoodSaver pulls enough vacuum to pull all the air bubbles out of a solution. There isn't really any question about compressing watermelon: it isn't strong enough to do it. But it is great for most sous vide applications and is MUCH less expensive than machines that pull enough vac to compress watermelon significantly.

Right. For actual sous vide cooking, there is nothing wrong with using a FoodSaver or "semipro" edge sealing vacuum machine. For a very small number of tricks, you'll need a chamber machine.

(Question: what about putting a weighted plate on top of the bagged watermelon when it is being vac'ed and then leaving the plate on? Note: I am thinking out loud without thinking it through -- so don't flame me if this is an idiotic idea.)

I think that, once you sealed the bag, there would be noplace for the "extra air" to go. So the weighted plate might crush the watermelon, but wouldn't compress the watermelon.

Maybe I can ask a naive question.  Once you remove enough air from the FS bag, does it matter if a higher vacuum is used?  Does it change the way you cook?

Short answer: No, it doesn't really matter for most sous vide applications.

There are certain tricks that one can do with sous vide equipment (although I am not sure I would call most of these sous vide cooking) that require a strong chamber machine.

[pounce]

How about a simple case:

3 ft of 1/4" vinyl tubing direct connected through an adapter to a vacuum gage or manometer.

Measure steady state low-side pressure after 1 minute of pump operation.

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I had an 8' piece of 1/4 hose I didn't want to cut so I left it at 8'. A FS handheld Wine Saver vacuum unit showed 24 hg at 1 minute. A FS v1085 showed 22.5hg at 1 minute. A venturi vacuum I have registered 27.8hg at 1 minute.

The vacuum gauge I used was an inexpensive automotive vacuum/pressure gauge.

I generally use the Wine Saver unit with the FS canisters, wine stoppers and Handi-Vac bags.

[DocDougherty]

A FS handheld Wine Saver vacuum unit showed 24 hg at 1 minute.

A FS v1085 showed 22.5hg at 1 minute.

A venturi vacuum I have registered 27.8hg at 1 minute.

The vacuum gauge I used was an inexpensive automotive vacuum/pressure gauge.

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Thanks for taking the time and effort. This seems to indicate that a typical FS leaves at least couple of psi of residual pressure in a bag, and I am pretty sure that a chamber vacuum machine leaves less.

I am trying to relate this to the effective buoyancy of the residual trapped air and my observation that I generally need to put about a handful of glass beads in a large bag to keep it from floating.

[e_monster]

The FoodSaver is strong enough to get most of the air out of a bag.

If you are left with so much air that the bag floats, it may be that your FoodSaver is defective or old or that you are placing the food in a position that makes it difficult to get the last residual air bubbles. I recently replaced a four year-old FoodSaver because it was frequently leaving too much air in the bag. Since I replaced it, I haven't had any problems with floating bags. Pounce's check valve method is also useful for venting any air bubbles that expand during cooking. (Fortunately, I haven't needed to use that method since getting the new FoodSaver)

Where you place the food in the bag can make a difference in whether too much air gets trapped in the bag. Also, the stiffness of the bags can be a factor. I have found that putting an empty bag under running hot water can soften the material so that the FS doesn't have to fight so much.

I find that the models with the Pulse vac option work better than the old FoodSaver that I replaced. (But that might be because mine had become so long in the tooth).

[slkinsey]

I'll add my voice to those who have never had a problem with bags floating when using a FS-type machine.

[dougal]

A FS handheld Wine Saver vacuum unit showed 24 hg at 1 minute.

A FS v1085 showed 22.5hg at 1 minute.

A venturi vacuum I have registered 27.8hg at 1 minute.

The vacuum gauge I used was an inexpensive automotive vacuum/pressure gauge.

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Thanks for taking the time and effort. This seems to indicate that a typical FS leaves at least couple of psi of residual pressure in a bag, and I am pretty sure that a chamber vacuum machine leaves less.

No, please, no!

Surely this has been done to death?

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.

I am trying to relate this to the effective buoyancy of the residual trapped air and my observation that I generally need to put about a handful of glass beads in a large bag to keep it from floating.

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However, a stronger pump will more quickly/effectively/completely pump out air that is 'trapped' and which only has tiny channels to escape through (to the pump).

Also a stronger pump will be able to produce more stretching of the plastic film, so that it fits more tightly around the food, but the pressure difference while pumping is going to be relieved rather quickly by the bag stretching as a result of any (temporary) pressure difference. And thermoplastics 'creep' faster still at 50C and above ...

And a stronger pump (volume as well as pressure) should cope better with leaky sealing lips on te machine...

What you want to end up with is the smallest practical volume of residual trapped air. A stronger pump will help a bit, but mostly the limitations are going to be seals and technique, rather than a 5% or so difference in maximum sustained pressure difference. (Note that the U-tube manometer testing above was using the 'accessory connector' and not the bag nozzle with its imperfect sealing.)

"A handful of glass beads" sounds like a lot of buoyancy, a lot of remaining air.

Doc, your problem could be that your pump isn't sucking properly. But it could equally well be that the soft 'lips' that seal the bag to the pump (and away from the room) aren't effective enough at preventing/restricting 'new' air leaking from room to pump (for whatever reason - wear, dirt, misassembly, whatever). Or that you are using inappropriate bags (the textured ones evacuate more completely more easily). Or, hey, it could be technique...

One technique to try is sealing as you do now, but then following that by snipping off a corner (small as you can), and re-introducing the pump nozzle through this small hole, re-evacuating and resealing. The bag will look kinda strange, but usually much better evacuated.

One cheapskate technique is to use just a strip of the (more expensive) textured plastic inside a plain bag, arranged so as to provide a pathway for air from the food area to the neighbourhood of the pump nozzle.

Hopefully, some of that will make some sense and be some help... !

[Vicious Wadd]

Question about short ribs:

As I type this, some short ribs are bathing at 151F. I'm loosely basing the temperature and cooking time on Daniel's 30 hour short ribs. Two questions:

(1) Dinner time will be at approx. the 25 hour mark. Will the difference of 5 hours make or break this dish?

(2) Anyone use Chinese Five Spice in SV preparations? I've read that some seasonings can get overpowering with prolonged cooking times. I hope this isn't one of them.

Best,

- VW

[Ruth]

If you have a good five spice powder (preferably one you made yourself) there should be no problem. There are some that have a chemical taste. As for the timing they will definitely be cooked but possibly not quite as tender as Daniel's version

[Vicious Wadd]

Thank Ruth. I ate them last night and I would say, next time, I will back off a bit on the five spice. As to tenderness, what you predicted turned out to be true. They were very good and tender, but not quite as fork-tender as I would have liked. That said, of the sous vide meats I have cooked so far, this has to be my favorite and I will definitely be experimenting with short ribs in the future.

Best Regards,

- VW

[pounce]

I hope Nathan doesn't mind, but there is a great video of Nathan talking at a TED conference about various topics, but maybe halfway through he talks about and shows some images of experimenting with cooking temps for beef. I thought others might be interested.

http://www.ted.com/talks/view/id/271

The whole video is very interesting, but if you want to skip to the cooking part and skip the whale sex, search for aliens and the invisibility cloak stuff head to about 8 minutes into the segment.